MF研究者総覧

研究者データベース

詳細
横澤　宏一(ヨコサワ　コウイチ)
保健科学研究院　保健科学部門　健康科学分野
教授
researchmap個人ページ
Last Updated :2024/05/09

基本情報

所属

  • 保健科学研究院　保健科学部門　健康科学分野

職名

  • 教授

学位

  • 博士（工学）（北海道大学）

ホームページURL

J-Global ID

研究キーワード

  • 脳磁界   脳情報   情報処理   認知機能   

研究分野

  • ライフサイエンス / 生体材料学
  • ライフサイエンス / 生体医工学

担当教育組織

研究活動情報

論文

  • Risa Anada, Hayato Watanabe, Atsushi Shimojo, Hideaki Shiraishi, Koichi Yokosawa
    Cerebral Cortex 34 2 1 - 12 2024年01月31日 [査読有り]
  • Nano Yoneta, Hayato Watanabe, Atsushi Shimojo, Kazuyoshi Takano, Takuya Saito, Kazuyori Yagyu, Hideaki Shiraishi, Koichi Yokosawa, Jared Boasen
    Frontiers in Neuroscience 16 790057 - 790057 2022年08月02日 [査読有り][通常論文]
     
    Auditory communication is an essential form of human social interaction. However, the intra-brain cortical-oscillatory drivers of auditory communication exchange remain relatively unexplored. We used improvisational music performance to simulate and capture the creativity and turn-taking dynamics of natural auditory communication. Using magnetoencephalography (MEG) hyperscanning in musicians, we targeted brain activity during periods of music communication imagery, and separately analyzed theta (5-7 Hz), alpha (8-13 Hz), and beta (15-29 Hz) source-level activity using a within-subjects, two-factor approach which considered the assigned social role of the subject (leader or follower) and whether communication responses were improvisational (yes or no). Theta activity related to improvisational communication and social role significantly interacted in the left isthmus cingulate cortex. Social role was furthermore differentiated by pronounced occipital alpha and beta amplitude increases suggestive of working memory retention engagement in Followers but not Leaders. The results offer compelling evidence for both musical and social neuroscience that the cognitive strategies, and correspondingly the memory and attention-associated oscillatory brain activities of interlocutors during communication differs according to their social role/hierarchy, thereby indicating that social role/hierarchy needs to be controlled for in social neuroscience research.
  • Hayato Watanabe, Atsushi Shimojo, Kazuyori Yagyu, Tsuyoshi Sonehara, Kazuyoshi Takano, Jared Boasen, Hideaki Shiraishi, Koichi Yokosawa, Takuya Saito
    PloS one 17 6 e0270090  2022年 
    Communication is one of the most important abilities in human society, which makes clarification of brain functions that underlie communication of great importance to cognitive neuroscience. To investigate the rapidly changing cortical-level brain activity underlying communication, a hyperscanning system with both high temporal and spatial resolution is extremely desirable. The modality of magnetoencephalography (MEG) would be ideal, but MEG hyperscanning systems suitable for communication studies remain rare. Here, we report the establishment of an MEG hyperscanning system that is optimized for natural, real-time, face-to-face communication between two adults in sitting positions. Two MEG systems, which are installed 500m away from each other, were directly connected with fiber optic cables. The number of intermediate devices was minimized, enabling transmission of trigger and auditory signals with almost no delay (1.95-3.90 μs and 3 ms, respectively). Additionally, video signals were transmitted at the lowest latency ever reported (60-100 ms). We furthermore verified the function of an auditory delay line to synchronize the audio with the video signals. This system is thus optimized for natural face-to-face communication, and additionally, music-based communication which requires higher temporal accuracy is also possible via audio-only transmission. Owing to the high temporal and spatial resolution of MEG, our system offers a unique advantage over existing hyperscanning modalities of EEG, fNIRS, or fMRI. It provides novel neuroscientific methodology to investigate communication and other forms of social interaction, and could potentially aid in the development of novel medications or interventions for communication disorders.
  • 柳生 一自, 渡辺 隼人, 高野 一義, 下條 暁司, 白石 秀明, 横澤 宏一, 齊藤 卓弥
    臨床神経生理学 48 5 440 - 440 (一社)日本臨床神経生理学会 2020年10月
  • Koichi Yokosawa, Keisuke Kimura, Ryoken Takase, Yui Murakami, Jared Boasen
    PLOS ONE 15 9 e0239577 - e0239577 2020年09月28日 [査読有り]
  • Kazuyoshi Takano, Hayato Watanabe, Kazuyori Yagyu, Atsushi Shimojo, Jared Boasen, Yui Murakami, Hideaki Shiraishi, Koichi Yokosawa, Takuya Saito
    2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) 2020 2893 - 2896 2020年07月 [査読有り]
     
    Face to face communication is interactive, and involves continuous feedforward and feedback of information, thoughts, and feelings to the opposite party. To accurately assess the neural processing underlying these interactions, synchronous and simultaneous recording of the brain activity from both parties is needed, a method known as hyperscanning. Here, we investigated the neural processing underlying nonverbal face-to-face communication using a magnetoencephalographic (MEG) hyperscanning system, comprising two fiber optically connected MEGs. Eight pairs of subjects participated. Each individual in each pair viewed a combined 80 randomized 20 s trials of 40 real-time and 40 recorded (hereafter, real and simulated, respectively) videos of the opposite party's face. Non-verbal communication through actions such as gaze, eye blinks, and facial expression was intrinsically only possible during real videos. After each trial, subjects individually subjectively discriminated whether the viewed video was real or simulated. Overall subjective discrimination accuracies were slightly but significantly above chance level. Statistical analysis of brain activity revealed a significant three way interaction between theta-band rhythm amplitude, video type, and subjective discrimination response in the right frontal cortex. Additionally, when subjects responded that videos were simulated, theta activity was significantly lower for real videos compared with simulated videos (p = 0.01). This result not only demonstrates the importance of right frontal theta activity during non-verbal communication, but also indicates the existence of unconscious, semi-automated neural processing during non-verbal communication that underlies one's ability to subjectively discriminate whether or not the opposite party is real.
  • Rie Matsunaga, Pitoyo Hartono, Koichi Yokosawa, Jun-ichi Abe
    Music Perception 37 3 225 - 239 2020年02月01日 [査読有り][通常論文]
     
    Tonal schemata are shaped by culture-specific music exposure. The acquisition process of tonal schemata has been delineated in Western mono-musical children, but cross-cultural variations have not been explored. We examined how Japanese children acquire tonal schemata in a bi-musical culture characterized by the simultaneous, and unbalanced, appearances of Western (dominant) music along with traditional Japanese (non-dominant) music. Progress of this acquisition was indexed by gauging children’s sensitivities to musical scale membership (differentiating scale-tones from non-scale-tones) and differences in tonal stability among scale tones (differentiating the tonic from another scale tone). Children (7-, 9-, 11-, 13-, and 14-year-olds) and adults judged how well two types of target tones (scale tone vs. non-scale tone; tonic vs. non-tonic) fit a preceding Western or traditional Japanese tonal context. Results showed that even 7-year-olds showed sensitivity to Western scale membership while sensitivity to Japanese scale membership did not appear until age nine. Also, sensitivity to the tonic emerged at age 13 for both types of melodies. These results suggest that even though they are exposed to both types of music simultaneously from birth, Japanese children begin by acquiring the tonal schema of the dominant Western music and this age of acquisition is not delayed relative to Western mono-musical peers.
  • Koichi Yokosawa
    Advanced Biomedical Engineering 9 0 217 - 224 2020年 [査読有り]
  • Ryoken Takase, Jared Boasen, Koichi Yokosawa
    2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) 2019年07月 [査読有り][通常論文]
  • リアルタイムコミュニケーションを計測するためのdual MEGシステムの構成
    渡辺 隼人, 下條 暁司, 柳生 一自, 曽根原 剛志, 白石 秀明, 横澤 宏一, 齊藤 卓弥
    日本生体磁気学会誌 32 1 158 - 159 日本生体磁気学会 2019年
  • Hong-Seng Gan, Tatsuya Suzuki, Koichi Yokosawa, Yumie Ono
    Advanced Biomedical Engineering 8 23 - 29 2019年
  • 脳磁計（MEG）の50年
    横澤宏一
    生体医工学 57 4-5 113 - 118 2019年 [査読無し][招待有り]
  • Appearance and modulation of a reactive temporal-lobe 8–10-Hz tau-rhythm
    Koichi Yokosawa, Yui Murakami, Hiroaki Sato
    Neuroscience Research 2019年 [査読有り][通常論文]
  • Akira Toyomura, Koichi Yokosawa, Atsushi Shimojo, Tetsunoshin Fujii, Shinya Kuriki
    J Neurosci Methods 307 14 - 22 2018年09月 [査読有り][通常論文]
     
    BACKGROUND: Locomotion, which is one of the most basic motor functions, is critical for performing various daily-life activities. Despite its essential function, assessment of brain activity during lower-limb movement is still limited because of the constraints of existing brain imaging methods. NEW METHOD: Here, we describe an MR-compatible, cylindrical treadmill device that allows participants to perform stepping movements on an MRI scanner table. The device was constructed from wood and all of the parts were handmade by the authors. RESULTS: We confirmed the MR-compatibility of the device by evaluating the temporal signal-to-noise ratio of 64 voxels of a phantom during scanning. Brain activity was measured while twenty participants turned the treadmill with feet in sync with metronome sounds. The rotary speed of the cylinder was encoded by optical fibers. The post/pre-central gyrus and cerebellum showed significant activity during the movements, which was comparable to the activity patterns reported in previous studies. Head movement on the y- and z-axes was influenced more by lower-limb movement than was head movement on the x-axis. Among the 60 runs (3 runs × 20 participants), head movement during two of the runs (3.3%) was excessive due to the lower-limb movement. COMPARISON WITH EXISTING METHODS: Compared to MR-compatible devices proposed in the previous studies, the advantage of this device may be simple structure and replicability to realize stepping movement with a supine position. CONCLUSIONS: Collectively, our results suggest that the treadmill device is useful for evaluating lower-limb-related neural activity.
  • Akira Toyomura, Tetsunoshin Fujii, Koichi Yokosawa, Shinya Kuriki
    Neuroscience 374 144 - 154 2018年03月15日 [査読有り][通常論文]
     
    Affective states, such as anticipatory anxiety, critically influence speech communication behavior in adults who stutter. However, there is currently little evidence regarding the involvement of the limbic system in speech disfluency during interpersonal communication. We designed this neuroimaging study and experimental procedure to sample neural activity during interpersonal communication between human participants, and to investigate the relationship between the amygdala activity and speech disfluency. Participants were required to engage in live communication with a stranger of the opposite sex in the MRI scanner environment. In the gaze condition, the stranger gazed at the participant without speaking, while in the live conversation condition, the stranger asked questions that the participant was required to answer. The stranger continued to gaze silently at the participant while the participant answered. Adults who stutter reported significantly higher discomfort than fluent controls during the experiment. Activity in the right amygdala, a key anatomical region in the limbic system involved in emotion, was significantly correlated with stuttering occurrences in adults who stutter. Right amygdala activity from pooled data of all participants also showed a significant correlation with discomfort level during the experiment. Activity in the prefrontal cortex, which forms emotion regulation neural circuitry with the amygdala, was decreased in adults who stutter than in fluent controls. This is the first study to demonstrate that amygdala activity during interpersonal communication is involved in disfluent speech in adults who stutter.
  • フィンランドの教育 そのしくみと成果
    横澤宏一
    臨床検査学教育 11 1 38 - 41 2018年 [査読無し][招待有り]
  • R. Matsunaga, T. Yasuda, M. Johnson-Motoyama, P. Hartono, K. Yokosawa, J. Abe
    Psychomusicology: Music, Mind, and Brain 28 3 178 - 188 2018年 [査読有り][通常論文]
  • Multiple Brain Activities during Sequential Memory Encoding ―MEG Study of Modulation of Alpha-band Rhythm
    Koichi Yokosawa, Ryoken Takase, Ryota Chitose, Keisuke Kimura
    Conference proceedings of IEEE Engineering in Medicine and Biology Society (EMBS) 5 - 8 2018年 [査読有り][通常論文]
  • Spectral-spatial Differentiation of Brain Activity during Mental Imagery of Improvisational Music Performance using MEG
    Jared Boasen, Yuya Takeshita, Shinya Kuriki, Koichi Yokosawa
    Frontiers in Human Neuroscience 12 Article 156  2018年 [査読有り][通常論文]
  • Akira Toyomura, Koichi Yokosawa, Shinya Kuriki
    Advanced Biomedical Engineering 6 15 - 20 公益社団法人 日本生体医工学会 2017年 [査読有り][通常論文]
     

    Bipedal locomotion requires an automatic process for rhythmic motor generation, as well as volitional and precise motor control for purposeful action. The neural substrates for these two distinct locomotion controls in humans are still unclear. This functional magnetic resonance imaging (MRI) study investigated the neural activity of the locomotor-related brain regions along with participants' lower limb behavior. Participants lay face-up in the MRI bore and moved their legs up and down at the knees under two conditions. Under the non-obstacle condition, they moved their legs while watching a point-of-view video that showed walking straight along a corridor at a constant speed. On the other hand, under the obstacle condition, the point-of-view video showed walking while avoiding obstacles in the passage. Two white markers were pasted on the soles of the participants' feet and images were captured by a video camera throughout the experiment to track the participants' lower limb movements. The horizontal fluctuation of lower limb movement was extracted offline. We assumed that the horizontal fluctuation reflected participants' volitional behavior of lower limb movement. The results showed that the obstacle condition elicited greater fluctuation of lower limb movement compared to the non-obstacle condition, and elicited brain activation in wider areas including the parietal and occipital lobes compared to the non-obstacle condition. The involvement of the parietal and occipital lobes in volitional control is consistent with findings of previous animal studies. In a correlation analysis between the signal change extracted from the locomotor-related cortical/subcortical regions and the horizontal fluctuation of the feet, activities in the cortical motor areas (primary motor cortex, premotor cortex, and supplementary motor area) showed weak but significant correlation with the fluctuation of lower limb movement. Activities in the cerebellar and mesencephalic locomotor regions showed no significant correlation, but almost constant activation irrespective of fluctuation of the lower limbs. These results suggest that the parietal, occipital cortices, and cortical motor areas are involved in volitional control.

  • Mizobe Kayo, Yokosawa Koichi, Shimojo Atsushi, Ozaki Michitaka
    Advanced Biomedical Engineering 5 88 - 93 2016年12月 [査読有り][通常論文]
     
    ストレスが身体機能に与える影響を評価することを目的に、健常者20名(平均21.3±1.3歳)に情動的快・中性・不快な画像刺激をランダムに呈示した際の主観的評価(VAS)、脳磁図、脈拍数、酸素飽和度(SpO2)を計測した。平常時に実験を行った被験者を対照群、12〜15時間絶食した状態で実験を行った被験者を絶食群とした。20名のうち、3名の脳磁図は信号源が特定できなかったため除外し、17名を分析対象とした。その結果、顕著な振幅変化が初期ステージ(画像提示後0.5〜1.75秒)に見られた。対照群ではα帯域律動が中性画像よりも快・不快画像で有意に抑制され、絶食群では快画像より不快画像でα帯域律動が有意に抑制された。絶食時には快画像に対する応答の低下がみられたことから、絶食時は情動的刺激に対する感受性が変化する可能性があることが示された。
  • 豊村 暁, 横澤 宏一, 下條 暁司, 藤井 哲之進, 栗城 眞也
    生体医工学 54 27 S199 - S199 一般社団法人 日本生体医工学会 2016年 

    ヒトの二足歩行に関する神経基盤は，主に計測上の制約からこれまで研究が進んでいない．本研究ではまず，MRI環境で使用可能な非磁性下肢運動装置を開発した．次に，ファントムを用いて，fMRIで用いられる高速撮像法において画像への影響がほとんど見られないことを，装置無し，装置静止時，および装置稼動時の比較によって確認した．次に，MRI内に被験者を入れて実際に計測を試みた．レスト時と下肢運動課題時を比較した場合，足の領域に相当する運動野背側部の領域が広く活動することが観察された．本装置はヒトの下肢運動に関する神経基盤の研究を始め，リハビリテーションの評価などに使用可能であると考えられる．

  • Koichi Yokosawa, Keisuke Kimura, Ryota Chitose, Takuya Momiki, Shinya Kuriki
    2016 38TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) 4539 - 4542 2016年 [査読有り][通常論文]
     
    Alpha-band rhythm is thought to be involved in memory processes, similarly to other spontaneous brain rhythms. Ten right-handed healthy volunteers participated in our proposed sequential short-term memory task that provides a serial position effect in accuracy rate. We recorded alpha-band rhythms by magnetoencephalography during performance of the task and observed that the amplitude of the rhythm was suppressed dramatically in the memory recall period. The suppressed region was estimated to be in the occipital lobe, suggesting that alpha-band rhythm is suppressed by activation of the occipital attentional network. Additionally, the alpha-band suppression reflected accuracy rate, that is, the amplitude was suppressed more when recalling items with higher accuracy rate. The sensors with a significant correlation between alpha-band amplitude and accuracy rate were located widely from the frontal to occipital regions mainly in the right hemisphere. The results suggests that alpha-band rhythm is involved in memory recall and can be index of memory performance.
  • Keisuke Kimura, Ryota Chitose, Koichi Yokosawa
    Advanced Biomedical Engineering 5 43 - 48 一般社団法人 日本生体医工学会 2016年 [査読有り][通常論文]
     
    Alpha-band (8–13 Hz) rhythm during encoding of sequentially presenting memory items was recorded using a 76-channel magnetoencephalograph. In a memory task, seven images each with an arrow pointing up, down, left or right were presented sequentially. Thereafter, a recall number was presented. Each participant memorized the arrow directions in the order of presentation and recalled the direction of the arrow for the recall number, and responded by pressing a button. Each participant also took part in a control task, in which the participant looked at the same images as those in the memory task but pressed the button previously instructed. Ten right-handed male volunteers performed 280 epochs of the memory task and 120 epochs of control task. The amplitudes of alpha-band rhythm during presentation of midterm (3rd–5th) items were compared with those of beginning (1st and 2nd) items. Fifteen sensors showed significant differences (midterm > beginning) in the memory task (0.01 < p < 0.05 at 11 sensors, 0.001 < p < 0.01 at 4 sensors), while no sensors showed a significant increase in the control task. Using the statistical parametric mapping (SPM) method, the region of increase in alpha-band rhythm from beginning to midterm was estimated to be located in the visual cortex and around bilateral temporal gyri. Additionally, the increase in amplitude from beginning to midterm was significantly greater before a correct answer than before a wrong answer (0.01 < p < 0.05 at 7 sensors and p < 0.001 at 1 sensor). Previous works demonstrated that alpha-band rhythm is increased by active inhibition of visual inputs that are irrelevant to memory. The region of increase estimated to be in the visual cortex agrees with previous works. An interpretation of our results is that since irrelevant visual inputs are successfully inhibited before a correct answer, the amplitude of alpha-band rhythm increases more than that before a wrong answer. These results indicate the possibility that alpha-band amplitude during memory encoding can be used as an index of memory performance.
  • 竹下悠哉, 角屋智香, 木村勁介, 松永理恵, 栗城眞也, 横澤宏一
    生体医工学 53 2 84 - 89 2015年06月01日 [査読有り][通常論文]
     
    We examined whether auditory steady-state response (ASSR), which is known as a lower-order brain response, can be modulated by expectations accompanying the progression of a musical phrase. We fabricated musical melodies consisted of seven tones, the amplitudes of which were modulated at 40Hz, under two conditions:the final (7th) tone was either congruent or incongruent with respect to the musical context of the melodies. Two control experiments were also conducted. The objective of one control experiment was to investigate the effect of the preceding sound (6th) on the final tone (7th) by presenting two final tones (6th and 7th) extracted from the melodies, and the objective of the other control experiment was to investigate the effect of hearing a pitch itself by presenting a tone sequence of ascending and descending scales between A♭5 and C7. The ASSR source strengths were estimated by magnetoencephalography. The strength of the 7th tone of the melodies was significantly larger in the incongruent condition than in the congruent condition. This difference could not be explained by effects of the preceding sound and pitch of the target tone, suggesting that ASSR was modulated by musical expectancy.
  • シーケンシャル記憶課題の記銘時におけるα波帯域脳律動の変調メカニズム
    千年涼太, 山路萌, 栗城眞也, 横澤宏一
    電子情報通信学会技術報告 114 514 177 - 182 2015年03月 [査読無し][通常論文]
  • リズム変化音列に対する脳磁界応答
    竹下悠哉, 田村菜月, 横澤 宏一
    電子情報通信学会技術報告 114 514 377 - 380 2015年03月 [査読無し][通常論文]
  • Yuya Takeshita, Koichi Yokosawa
    2015 37TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) 6650 - 6653 2015年 [査読有り][通常論文]
     
    Rhythm is an element of music and is important for determining the impression of the music. To investigate the mechanism by which musical rhythmic changes are perceived, magnetoencephalographic responses to rhythm deviants were recorded from 11 healthy volunteers. Auditory stimuli consisting of physically controlled tones were adapted from a song. The auditory stimuli had a steady rhythm, but "early" and "late" deviants were inserted. Only the "early" deviant, which was a tone with a short duration, caused N100m-like prominent transient responses at around the offset of the deviant tone. The latency of the prominent response depended on the descending sound pressure of the deviant tone and was 65 ms after 50% descent. The results suggest that unexpected shortening of tone in a continuous rhythm evokes a transient response and that the response is caused by descending sound pressure of the shortened tone itself, not by the following tones.
  • Ruokang Han, Taiki Takahashi, Akane Miyazaki, Tomoka Kadoya, Shinya Kato, Koichi Yokosawa
    2015 37TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) 6646 - 6649 2015年 [査読有り][通常論文]
     
    Impulsivity dictates individual decision-making behavior. Therefore, it can reflect consumption behavior and risk of addiction and thus underlies social activities as well. Neuroscience has been applied to explain social activities; however, the brain function controlling impulsivity has remained unclear. It is known that impulsivity is related to individual time perception, i. e., a person who perceives a certain physical time as being longer is impulsive. Here we show that activity of the left auditory cortex is related to individual impulsivity. Individual impulsivity was evaluated by a self-answered questionnaire in twelve healthy right-handed adults, and activities of the auditory cortices of bilateral hemispheres when listening to continuous tones were recorded by magnetoencephalography. Sustained activity of the left auditory cortex was significantly correlated to impulsivity, that is, larger sustained activity indicated stronger impulsivity. The results suggest that the left auditory cortex represent time perception, probably because the area is involved in speech perception, and that it represents impulsivity indirectly.
  • Mika Omatsu, Takayuki Obata, Kazuyuki Minowa, Koichi Yokosawa, Eri Inagaki, Kinya Ishizaka, Koichi Shibayama, Toru Yamamoto
    JOURNAL OF MAGNETIC RESONANCE IMAGING 40 6 1481 - 1486 2014年12月 [査読有り][通常論文]
     
    PurposeTo evaluate the effect of the static magnetic field of magnetic resonance (MR) scanners on keepers (ie, ferromagnetic stainless steel plate adhered to the abutment tooth of dental magnetic attachments). Materials and MethodsMagnetically induced displacement force and torque on keepers were measured using 1.5 Tesla (T) and 3.0 T MR scanners and a method outlined by American Society for Testing and Materials (ASTM). Changes in magnetic flux density before and after exposure to scanner static magnetic field were examined. ResultsThe maximum magnetically induced displacement forces were calculated to be 10.3 x 10(-2) N at 1.5 T and 13.9 x 10(-2) N at 3.0 T on the cover surface. The maximum torques exerted on the keeper (4 mm in diameter) were 0.83 N x 4 mm at 1.5 T and 0.85 N x 4 mm at 3.0 T. These forces were considerably higher than the gravitational force (7.7 x 10(-4) N) of the keeper but considerably lower than the keeper-root cap proper adhesive force. The keepers' magnetic flux density remained less than that of the Earth. ConclusionMagnetically induced displacement force and torque on the keeper in the MR scanner do not influence the keeper-root cap proper adhesive force.J. Magn. Reson. Imaging 2014;40:1481-1486. (c) 2013 Wiley Periodicals, Inc.
  • Akira Toyomura, Tetsunoshin Fujii, Koichi Yokosawa, Shinya Kuriki
    Transactions of Japanese Society for Medical and Biological Engineering 52 157 - O-158 2014年08月17日 [査読有り][通常論文]
     
    Stuttering is a developmental disorder of speech fluency. It is known that stuttering speakers can fluently speak when they speak by themselves, but stuttering appears well when they speak under face-to-face condition. This phenomenon is well known but the mechanism is still unclear. In general, vocal communication of face-to-face induces a certain level of stress comparing to speaking to oneself. This stress may have influence on speech motor production. In this study, we attempted to construct the experimental setup for face-to-face communication in MRI environment. There were four conditions 1) question by another participant in console room, 2) question presented on the screen, 3) look a face of another participant, and 4) a rest condition. Preliminary results showed that there were difference of neural activity between the conditions and speaker groups in the motor or sensory areas.
  • 溝部 佳代, 横澤 宏一, 澤部 祐貴, 太田 早紀, 河村 優生, 半谷 早紀枝, 下條 暁司, 尾崎 倫孝
    日本生体磁気学会誌 27 1 160 - 161 日本生体磁気学会 2014年05月
  • 音楽的旋律の期待による聴覚性定常応答の変調
    角屋智香, 竹下悠哉, 栗城眞也, 横澤宏一
    電子情報通信学会技術報告 113 500 203 - 208 2014年03月 [査読無し][通常論文]
  • Rie Matsunaga, Koichi Yokosawa, Jun-ichi Abe
    NEUROPSYCHOLOGIA 54 1 - 10 2014年02月 [査読有り][通常論文]
     
    Bilingual studies have shown that brain activities for first (L1) and second (12) languages are influenced by L2 proficiency. Does proficiency with a second musical system (M2) influence bimusical brains in a manner similar to that of bilingual brains? Our magnetoencephalography study assessed the influence of M2 proficiency on the spatial, strength, and temporal properties of brain activity in a musical syntactic-processing task (i.e., tonal processing) involving first (M1) and second (M2) music systems. Two bimusical groups, differing in M2 proficiency (high, low), listened to melodies from both their M1 and M2 musical cultures. All melodies ended with a tonally consistent or inconsistent tone. In both groups, tonal deviations in both M1 and M2 elicited magnetic early right anterior negativities (mERANs) that were generated from brain areas arouna the inferior frontal gyrus (IFG). We also analyzed the dipole locations, dipole strengths, and peak latencies of mERAN. Results revealed: (a) the distances between dipole locations for M1 and M2 were shorter in the M2 high-proficiency group than in the M2 lowproficiency group; (b) the dipole strengths were greater in the high than the low group; (c) the peak latencies of M2 were shorter in the high than low group. The dipole location results were consistent with those from bilingual studies in that the distances between the (left) IFG peak activations for Ll and L2 syntactic processing shortened as L2 proficiency increased. The parallel results for bimusicals and bilinguals suggest that the functional changes induced by proficiency in a second (linguistic or musical) system are defined by domain-general neural constraints. (C) 2013 Elsevier Ltd. All rights reserved.
  • 江戸末期の和本
    横澤宏一
    生体医工学 52 1 50  2014年 [査読無し][招待有り]
  • Koichi Yokosawa, Siina Pamilo, Lotta Hirvenkari, Riitta Hari, Elina Pihko
    PLOS ONE 8 11 e80284  2013年11月 [査読有り][通常論文]
     
    To study how auditory cortical processing is affected by anticipating and hearing of long emotional sounds, we recorded auditory evoked magnetic fields with a whole-scalp MEG device from 15 healthy adults who were listening to emotional or neutral sounds. Pleasant, unpleasant, or neutral sounds, each lasting for 6 s, were played in a random order, preceded by 100-ms cue tones (0.5, 1, or 2 kHz) 2 s before the onset of the sound. The cue tones, indicating the valence of the upcoming emotional sounds, evoked typical transient N100m responses in the auditory cortex. During the rest of the anticipation period (until the beginning of the emotional sound), auditory cortices of both hemispheres generated slow shifts of the same polarity as N100m. During anticipation, the relative strengths of the auditory-cortex signals depended on the upcoming sound: towards the end of the anticipation period the activity became stronger when the subject was anticipating emotional rather than neutral sounds. During the actual emotional and neutral sounds, sustained fields were predominant in the left hemisphere for all sounds. The measured DC MEG signals during both anticipation and hearing of emotional sounds implied that following the cue that indicates the valence of the upcoming sound, the auditory-cortex activity is modulated by the upcoming sound category during the anticipation period.
  • Shinya Kuriki, Koichi Yokosawa, Makoto Takahashi
    PLOS ONE 8 9 e75990  2013年09月 [査読有り][通常論文]
     
    The auditory illusory perception "scale illusion" occurs when a tone of ascending scale is presented in one ear, a tone of descending scale is presented simultaneously in the other ear, and vice versa. Most listeners hear illusory percepts of smooth pitch contours of the higher half of the scale in the right ear and the lower half in the left ear. Little is known about neural processes underlying the scale illusion. In this magnetoencephalographic study, we recorded steady-state responses to amplitude-modulated short tones having illusion-inducing pitch sequences, where the sound level of the modulated tones was manipulated to decrease monotonically with increase in pitch. The steady-state responses were decomposed into right- and left-sound components by means of separate modulation frequencies. It was found that the time course of the magnitude of response components of illusion-perceiving listeners was significantly correlated with smooth pitch contour of illusory percepts and that the time course of response components of stimulus-perceiving listeners was significantly correlated with discontinuous pitch contour of stimulus percepts in addition to the contour of illusory percepts. The results suggest that the percept of illusory pitch sequence was represented in the neural activity in or near the primary auditory cortex, i.e., the site of generation of auditory steady-state response, and that perception of scale illusion is maintained by automatic low-level processing.
  • 短期記憶課題の記銘時α波脳磁場振幅の変調
    横澤 宏一, 千年 涼太, 馬場 聡美, 椴木 拓也, 高橋 誠, 栗城 眞也
    電子情報通信学会技術報告 112 480 147 - 152 2013年03月 [査読無し][通常論文]
  • Satoshi Sakuraba, Hana Kobayashi, Shinya Sakai, Koichi Yokosawa
    2013 35TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) 6909 - 6912 2013年 [査読有り][通常論文]
     
    The human brain has two streams to process visual information: a dorsal stream and a ventral stream. Negative potential N170 or its magnetic counterpart M170 is known as the face-specific signal originating from the ventral stream. It is possible to present a visual image unconsciously by using continuous flash suppression (CFS), which is a visual masking technique adopting binocular rivalry. In this work, magnetoencephalograms were recorded during presentation of the three invisible images: face images, which are processed by the ventral stream; tool images, which could be processed by the dorsal stream, and a blank image. Alpha-band activities detected by sensors that are sensitive to M170 were compared. The alpha-band rhythm was suppressed more during presentation of face images than during presentation of the blank image (p=.028). The suppression remained for about 1 s after ending presentations. However, no significant difference was observed between tool and other images. These results suggest that alpha-band rhythm can be modulated also by unconscious visual images.
  • Koichi Yokosawa, Tatsuya Watanabe, Daichi Kikuzawa, Gakuto Aoyama, Makoto Takahashi, Shinya Kuriki
    2013 35TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) 6187 - 6190 2013年 [査読有り][通常論文]
     
    Detection of a collision risk and avoiding the collision are important for survival. We have been investigating neural responses when humans anticipate a collision or intend to take evasive action by applying collision-simulating images in a predictable manner. Collision-simulating images and control images were presented in random order to 9 healthy male volunteers. A cue signal was also given visually two seconds before each stimulus to enable each participant to anticipate the upcoming stimulus. Magnetoencephalograms (MEG) were recorded with a 76-ch helmet system. The amplitude of alpha band (8-13 Hz) rhythm when anticipating the upcoming collision-simulating image was significantly smaller than that when anticipating control images even just after the cue signal. This result demonstrates that anticipating a negative (dangerous) event induced event-related desynchronization (ERD) of alpha band activity, probably caused by attention. The results suggest the feasibility of detecting endogenous brain activities by monitoring alpha band rhythm and its possible applications to engineering systems, such as an automatic collision evasion system for automobiles.
  • Rie Matsunaga, Koichi Yokosawa, Jun-ichi Abe
    NEUROPSYCHOLOGIA 50 14 3218 - 3227 2012年12月 [査読有り][通常論文]
     
    Individuals who have been exposed to two different musical cultures (bimusicals) can be differentiated from those exposed to only one musical culture (monomusicals). Just as bilingual speakers handle the distinct language-syntactic rules of each of two languages, bimusical listeners handle two distinct musical-syntactic rules (e.g., tonal schemas) in each musical culture. This study sought to determine specific brain activities that contribute to differentiating two culture-specific tonal structures. We recorded magnetoencephalogram (MEG) responses of bimusical Japanese nonmusicians and amateur musicians as they monitored unfamiliar Western melodies and unfamiliar, but traditional, Japanese melodies, both of which contained tonal deviants (out-of-key tones). Previous studies with Western monomusicals have shown that tonal deviants elicit an early right anterior negativity (mERAN) originating in the inferior frontal cortex. In the present study, tonal deviants in both Western and Japanese melodies elicited mERANs with characteristics fitted by dipoles around the inferior frontal gyrus in the right hemisphere and the premotor cortex in the left hemisphere. Comparisons of the nature of mERAN activity to Western and Japanese melodies showed differences in the dipoles' locations but not in their peak latency or dipole strength. These results suggest that the differentiation between a tonal structure of one culture and that of another culture correlates with localization differences in brain subregions around the inferior frontal cortex and the premotor cortex. (C) 2012 Elsevier Ltd. All rights reserved.
  • 背側視覚経路は本当に道具カテゴリを処理しているのか？
    桜庭 聡, 境 信哉, 山中正紀, 横澤宏一, 平山和美
    北海道医学雑誌 87 6 256  2012年11月 [査読無し][招待有り]
  • 渡辺 隼人, 横澤 宏一, 久住 一郎, 室橋 春光
    生理心理学と精神生理学 30 2 144 - 144 日本生理心理学会 2012年08月
  • 視覚単一モーダルミスマッチ反応における脳磁界応答
    畑中亜翔, 横澤宏一, 高橋誠
    電子情報通信学会技術研究報告 111 483 377 - 380 2012年03月 [査読無し][通常論文]
  • 衝突模倣刺激を用いた運動の予測と知覚に伴うα波帯域脳磁場の振幅変調
    菊澤大地, 横澤宏一, 齋藤千尋, 竹内文也, 関原謙介
    電子情報通信学会技術研究報告 111 483 293 - 298 2012年03月 [査読無し][通常論文]
  • Satoshi Sakuraba, Shinya Sakai, Masanori Yamanaka, Koichi Yokosawa, Kazumi Hirayama
    JOURNAL OF NEUROSCIENCE 32 11 3949 - 3953 2012年03月 [査読有り][通常論文]
     
    Previously, Almeida et al. (2008) used a technique called Continuous Flash Suppression to show that human dorsal stream cortical areas specifically responded to a "tool category." Here, we used the same technique to clarify what attributes of tools are processed in the dorsal stream. We examined surface attributes and shape. A significant priming effect was found when we removed surface attributes by using line drawings instead of photographs. In a second experiment, we manipulated shape and we found that there were no significant priming effects when we used nonelongated tool pictures as tool prime stimuli. To better clarify the effect of shape attributes on priming effects, we conducted a further experiment using elongated stick-like rectangles as prime stimuli and found that elongated shapes significantly shortened the reaction time to the tool pictures as target stimuli. Additionally, when elongated vegetables were used as prime stimuli, the reaction time to the tool pictures as target stimuli was also significantly shortened, but there was no effect when stubby vegetables were used. Finally, when we controlled for orientation by presenting rotated elongated stick-like rectangles, diamond shapes, and cut circles as prime stimuli, we found that rectangles replicated the same significant priming effect as previous experiments, but the others did not. These results suggest that the dorsal stream processes elongated shapes but does not process the tool category specifically.
  • 純正律和音が与える印象と脳磁界活動の関係性の評価
    関大輔, 横澤宏一
    電子情報通信学会技術研究報告 111 483 371 - 376 2012年 [査読無し][通常論文]
  • Desynchronization of alpha-band rhythm related to retrieving short-term memory
    T. Momiki, K. Yokosawa, M. Sata, Y. Nakazono, M. Takahashi, S. Kuriki
    Proceedings of 2011 World Congress on Engineering and Technology 5 1 165 - 168 2011年10月 [査読有り][通常論文]
  • 椴木 拓也, 佐多 正至, 中園 嘉巳, 横澤 宏一, 高橋 誠, 栗城 眞也
    電子情報通信学会技術研究報告. NC, ニューロコンピューティング 110 461 401 - 406 一般社団法人電子情報通信学会 2011年02月28日 [査読無し][通常論文]
     
    短期記憶の想起の脳内機序の解明を目的として,記憶想起時の脳磁場の計測を試みた.記憶課題として被験者10名は連続で7個提示される矢印画像の方向(上下左右)を順番通りに記憶するよう努めた.さらに最後の矢印が提示された500ms後に提示される1から7までのいずれかの数字の順番に該当する矢印の方向を想起し,ボタン押しで回答した.コントロールとして記憶負荷のない同様の課題も行わせた.脳磁界データはボタン押しを基準として自発脳磁界を解析した.その結果,記憶負荷のある場合のみ,前頭部においてボタン押しの約2秒前から低周波自発リズム(1〜4Hz)の振幅増大(ERS)が観察された.本結果から,δ波帯域自発リズムと記憶想起の関連が示唆された.
  • 関 大輔, 横澤 宏一
    電子情報通信学会技術研究報告. NC, ニューロコンピューティング 110 461 143 - 146 一般社団法人電子情報通信学会 2011年02月28日 [査読無し][通常論文]
     
    和音には長和音,短和音,不協和音があり,それぞれ異なる印象を与える.本研究では,物理特性を極力統一して3種の和音を7個ずつ作成し,これらを提示した時の脳磁界活動を計測して,和音の種類間での活動の差異を自発リズムと誘発応答について評価した.また,行動実験を行い,和音聴取により得られる印象の度合いを数値化し,脳磁データとの相関を評価した.和音提示後の自発リズムの振幅変調に関して和音間で有意差が確認され,行動実験結果との相関も確認された.これらの結果は,和音の種類の差異は誘発応答よりも自発リズムの振幅変調の差異に反映されること,さらに,その差異は和音聴取により得られる印象と相関があることを示しており,自発リズムの変調により感情が定量計測できる可能性を示唆するものである.
  • N1m (M100) 潜時と自閉症傾向の関係に関する検討
    渡辺隼人, 横澤宏一, 室橋春光
    臨床神経生理学 39 5 405  2011年 [査読有り][通常論文]
  • MEG study of music processing in bimusicals
    Matsunaga R, Yokosawa K, Abe J
    International Journal of Bioeleoctromagnetism 13 4 239 - 244 2011年 [査読有り][通常論文]
  • 視覚情報回転変換・遅延環境における到達運動遂行時の脳磁界計測
    佐多正至, 中瀬洋人, 椴木拓也, 横澤宏一, 高橋誠
    第25回生理・生体工学シンポジウム論文集 333 - 336 2010年08月 [査読無し][通常論文]
  • 外的な音声と映像への発声の同調による神経活動の変調
    豊村 暁, 横澤 宏一, 鈴木 要, 栗城 眞也
    第25回生理・生体工学シンポジウム論文集 329 - 332 2010年08月 [査読無し][通常論文]
  • Prediction of vocalization using time-frequency information of mu rhythm
    A. Toyomura, K. Yokosawa, K. Suzuki, S. Kuriki
    Proceedings of the SICE2010 Annual conference 3407 - 3408 2010年08月 [査読有り][通常論文]
  • 豊村 暁, 横澤 宏一, 鈴木 要, 栗城 眞也
    電子情報通信学会技術研究報告. NLP, 非線形問題 110 122 29 - 32 一般社団法人電子情報通信学会 2010年07月05日 [査読無し][通常論文]
     
    運動のタイミングに合わせて外的な視聴覚刺激を与えると,例えば発声や歩行に関連した運動障害に対して運動機能促進効果があることが知られているが,その神経メカニズムは十分に調べられていない.本研究では,通常の発声の際に受聴している発声音声の聴覚フィードバック経路に,外的な聴覚刺激と視覚刺激を同期的に与えた場合の脳活動をMEG装置を用いて計測した.運動関連の神経リズムを反映する10Hzおよび20Hz帯に着目して時間周波数解析を行ったところ,自発的な発声条件に比べ,外的刺激に同期して発声する場合により強く事象関連脱同期現象(event related desynchronization: ERD)が観察された.また,視聴覚刺激を単に見ている場合でも,映像の発声付近で最も抑制される傾向にあった.これらの結果は,吃音における斉読効果のメカニズムとして,外的な視聴覚刺激が発声運動に関連する神経活動をより促進する,という説明が可能であることを示唆している.また,発声関連の脱同期現象の特定は,発話コミュニケーションにおけるBMI (Brain Machine Interface)などへの応用等も期待される.
  • 青山 岳人, 横澤 宏一, 栗城 眞也, 高橋 誠
    電子情報通信学会技術研究報告. NC, ニューロコンピューティング 109 461 357 - 362 一般社団法人電子情報通信学会 2010年03月02日 [査読無し][通常論文]
     
    本研究では,衝突とその予測段階における脳内メカニズムを明らかにすることを目的とした.被験者には衝突を模倣した視覚刺激と2種類のコントロール刺激を与えた.またそれらの刺激の2s前に,各刺激を予測させるための手がかり刺激を与え,脳磁界計測と解析を行った.その結果,手がかり刺激が提示されてから衝突を模倣した刺激が提示されるまでの期間で,α帯域の振幅がコントロール刺激に比べて有意に小さかった.この結果は,内因性の脳活動である「予測」によって生じた衝突模倣刺激の提示に先行した脳活動の変調を計測したものと考えられる.さらにブレイン-コンピューターインターフェイスへの応用展開を目指して,α帯域の振幅変調量から与えられた刺激が衝突模倣刺激かコントロール刺激かを単一エポックごとに弁別できるかどうかを検討した.60試行分のα帯域の振幅変調量を基準としたところ,最も正答率の高い被験者では79%の正答率が得られた.
  • 大内 健一, 横澤 宏一, 栗城 眞也, 高橋 誠
    電子情報通信学会技術研究報告. NC, ニューロコンピューティング 109 461 351 - 356 一般社団法人電子情報通信学会 2010年03月02日 [査読無し][通常論文]
     
    本研究では,周波数タグを利用して,左右の耳に与えた音情報の脳内処理を明らかにすることを目的とした.そのために,両耳性の聴覚反応の基本的な特性と,両耳間の相互干渉の結果として生じる錯聴現象(scale illusion)について,脳磁界計測と解析により調ペた.その結果,左右の音高が異なる刺激音を聴取した場合の反応は音高が左右で同一の場合に比べ,刺激のキャリヤ周波数に対する依存性が小さくなることが示された。また,音が連続してメロディーが聞こえることによる注意の効果により,脳半球特異的なタグ振幅の変調が生じ,比較的短時間(<1s)で変化する競合的メロディー音が左右の聴覚野で機能的に分化して処理されていることが示された.
  • 佐多 正至, 横澤 宏一, 高橋 誠
    電子情報通信学会技術研究報告. NC, ニューロコンピューティング 109 461 57 - 59 一般社団法人電子情報通信学会 2010年03月02日 [査読無し][通常論文]
     
    我々はこれまで,視覚と固有受容感覚の関係を時空間的に矛盾させた環境における上肢到達運動遂行時の運動軌跡および脳活動を解析することにより,前頭前野・運動前野における活動について検討を行ってきた.その結果,前頭前野では初期運動方向を評価していることを,運動前野は運動計画や修正運動の遂行に関与することを示唆した.現在,脳活動のタイミングをより明確にするために,時間分解能に優れた脳磁気計測(MEG)を用いた計測を検討している.しかしながら,磁性を有する位置計測装置をシールドルーム内に設置できないという問題点がある.そこで,非磁性材料であるナイロン糸を用いて手先位置を引っ張り,シールドルーム外から手先の変位を計測する到達運動計測システムを試作した.本手法により,脳磁気計測(MEG) と到達運動計測の併用が可能になると考える.
  • 短縮持続時間MMNmと延長持続時間MMNmの違いに関する検討
    渡辺隼人, 横澤宏一, 室橋春光
    臨床神経生理学 38 5 364  2010年 [査読有り][通常論文]
  • 二音階両耳刺激による定常応答の解析―左右聴覚野と2音階を弁別する手法―
    大内健一, 横澤宏一, 栗城眞也, 高橋 誠
    第24回生理・生体工学シンポジウム論文集 57 - 60 2009年09月 [査読無し][通常論文]
  • 視覚情報回転・遅延変換環境における到達運動遂行時の前頭葉の活動
    佐多正至, 中瀬洋人, 横澤宏一, 高橋誠
    第24回生理・生体工学シンポジウム論文集 89 - 92 2009年09月 [査読無し][通常論文]
  • 衝突の予測と視覚的知覚に伴う脳磁界応答
    青山 岳人, 横澤 宏一, 栗城眞也, 高橋 誠
    第24回生理・生体工学シンポジウム論文集 69 - 72 2009年09月 [査読無し][通常論文]
  • Effects of Auditory Attention on Oscillatory Activities around 10 Hz
    H. Tanaka, K. Yokosawa, A. Otsuka, S. Kuriki
    Biomagnetism; Interdisciplinary Research and Exploration 203 - 205 2008年08月 [査読無し][通常論文]
  • Koichi Yokosawa, Sadaki Nakano, Yasushi Goto, Kazuo Saitoh, Keiji Tsukada
    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING 3 2 229 - 235 2008年03月 [査読有り][通常論文]
     
    A prototype system for detecting hydrogen-gas leaks in hydrogen filling stations was fabricated. The prototype is composed of a wireless network with 10 sensor nodes for monitoring the spatial distribution of hydrogen-gas concentration. To make each sensor node to be driven by a battery, field-effect transistor (FET) sensors and a microprocessor with low power consumption were used. Additionally, two functions were devised and implemented in the microprocessor in each node: one reduces the power consumption of each sensor node and the other controls the transmission to avoid communication congestion when a gas leak occurs. The use of batteries and wireless communications enables the nodes to be placed at optimal sensing locations without regard to the wiring needed with existing gas sensors. (C) 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
  • Koichi Yokosawa, Kazuo Saitoh, Sadaki Nakano, Yasushi Goto, Keiji Tsukada
    SENSORS AND ACTUATORS B-CHEMICAL 130 1 94 - 99 2008年03月 [査読有り][通常論文]
     
    A method for heating field-effect-transistor (FET) gas sensors with minimum power is proposed. The time of the FET sensor response to target gases depends on temperatures of catalytic metals laminated on gate insulators. Therefore, maximum heating efficiency can be obtained by applying current to each catalytic metal directly and using those catalytic metals as heaters. FET hydrogen gas sensors have been fabricated on 7.5 mm x 3 mm x 0.73 mm silicon chips, and narrow palladium catalytic metal has been deposited and terminated by two electrodes. The FET sensor can be heated to 100 degrees C by applying current corresponding to 0.2 W, and the response speed to 1000 ppm by volume hydrogen gas increases by about a factor of six. No morphological change caused by the heating current has been observed in the catalytic metal. Moreover, numerical and experimental simulations demonstrate that the required power and time to heat the FET sensor to 100 degrees C can be further reduced to 20-30 mW and 1 s, respectively, by miniaturizing the senor chip to 2 mm x 2 mm x 0.15 mm. We are planning to apply the FET sensors with this heating method to our hydrogen-leak detection system that is being developed to make hydrogen energy structures safe and secure. Such detection systems consist of many sensor nodes powered by batteries, so reducing power consumption is important to extend battery lifetimes. (C) 2007 Published by Elsevier B.V.
  • T. Yamaguchi, T. Kiwa, K. Tsukada, K. Yokosawa
    SENSORS AND ACTUATORS A-PHYSICAL 136 1 244 - 248 2007年05月 [査読有り][通常論文]
     
    This paper reports the effect of oxygen in air on a Pt-FET hydrogen sensor. The output voltage change of the Pt-FET had good linearity to the logarithm of hydrogen concentration in nitrogen. The slope of the linear curve is -26.4 mV/decade, which is close to the calculated value of the Nemstian slope. This indicates the response mechanism of the Pt-FET sensor is based on the catalytic reaction on the Pt surface. However, the output voltage change of the Pt-FET was not proportional to the logarithm of hydrogen concentration in air due to adsorbed oxygen on the Pt surface. This indicates the water formation for the reaction of hydrogen and oxygen on the Pt surface is the main hydrogen response mechanism in air. (C) 2006 Elsevier B.V. All rights reserved.
  • Akira Tsukamoto, Daisuke Suzuki, Koichi Yokosawa, Akihiko Kandori, Yusuke Seki, Kuniomi Ogata, Tsuyoshi Miyashita, Kazuo Saitoh, Keiji Tsukada
    ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS 90 4 46 - 55 2007年 [査読有り][通常論文]
     
    As a new clinical examination apparatus for cardiac diseases, attention is focused on the magnetocardiograph, which can represent electrophysiological phenomena of the heart noninvasively as graphical information. We have been developing a compact and portable high-temperature superconducting magnetocardiograph based on our technology for magnetocardiographs using low-temperature superconductors. Since a high-temperature superconducting magnetocardiograph can work with liquid nitrogen cooling, it allows miniaturization and lower running costs. Hence, it is expected to help popularize magnetocardiographs by its use in smaller hospitals and in group medical examinations in the field. In this paper, we introduce the prototype high-temperature superconducting magnetocardiographs we have made, and report the fabrication technology for a highly sensitive high-temperature SQUID and the technology for external noise shielding and compensation. (C) 2007 Wiley Periodicals, Inc.
  • Recent Technologies of Magnetocardiography and Impedance Magnetocardiography: Review of the Literature
    A. Kandori, D. Suzuki, K. Saito, A. Tsukamoto, T. Miyashita, K. Tsukada, K. Yokosawa, K. Ogata, Y. Seki
    Progress in Superconductivity 8 1 1 - 7 2006年10月 [査読有り][招待有り]
  • 簡易小型磁気シールドを用いた高温超電導SQUIDマルチチャネル心磁計システム
    鈴木大介, 塚本晃, 宮下豪, 神鳥明彦, 緒方邦臣, 横澤宏一, 塚田啓二, 渡辺重行
    電子情報通信学会技術研究報告 SCE2006-12～24 61 - 66 2006年07月 [査読無し][通常論文]
  • 高温超伝導心磁計測システムの開発
    塚本晃, 鈴木大介, 横澤宏一, 神鳥明彦, 関悠介, 緒方邦臣, 宮下豪, 齋藤和夫, 塚田啓二
    電子情報通信学会和文論文誌C J89-C 3 95 - 103 2006年03月 [査読有り][通常論文]
  • K Tsukada, T Kiwa, T Yamaguchi, S Migitaka, Y Goto, K Yokosawa
    SENSORS AND ACTUATORS B-CHEMICAL 114 1 158 - 163 2006年03月 [査読有り][通常論文]
     
    The fast response characteristics of a Pt-FET hydrogen sensor have been investigated using a hydrogen gas flow system and a flow-through cell for the sensor. The Pt-FET hydrogen sensor showed good linear response, detecting hydrogen concentrations from 10 ppm to 10%, and had a sensitivity of -25.1 mV/decade at room temperature, which is close to the value for the Nemstian slope. The transient response characteristic shows that the equivalent catalytic reaction on the platinum surface is dominant in the response time. (c) 2005 Elsevier B.V. All rights reserved.
  • K. Yokosawa, S. Nakano, Y. Goto, K. Tsukada
    Proceedings of the 22nd Sensor Symposium on Sensors, Micromachines, and Applied Systems 435 - 438 2005年10月 [査読有り][通常論文]
  • A Tsukamoto, K Saitoh, K Yokosawa, D Suzuki, Y Seki, A Kandori, K Tsukada
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 426 1580 - 1584 2005年10月 [査読有り][通常論文]
     
    A high-throughput high-T-c SQUID fabrication process that can provide the appropriate number of SQUIDs for a 51-channel magnetocardiograph (MCG) has been developed. A new deposition system-based on a pulsed-laser-deposition technique to increase the process throughput in fabricating superconducting YBa2Cu3Oy, thin films-was developed. In this system, nine superconducting thin films are successively deposited on bicrystal substrates in one deposition sequence. A mask aligner, which was customized for the bicrystal substrate, was also developed. This system enables mask alignment for the bicrystal grain boundary without the need for preprocessing to visualize it. In addition, the magnetometer pattern was designed to improve the yield for magnetometer fabrication. In this directly coupled magnetometer, four SQUIDs were connected with the same pickup coil. Accordingly, the yield of magnetometer could be enhanced by selecting the best SQUID among the four. (c) 2005 Elsevier B.V. All rights reserved.
  • A Kandori, D Suzuki, A Tsukamoto, Y Kumagai, T Miyashita, K Ogata, Y Seki, K Yokosawa, K Tsukada
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 9A 6513 - 6518 2005年09月 [査読有り][通常論文]
     
    We aimed to develop a control system for multichannel magnetocardiography (MCG) based on a high-temperature DC superconducting quantum interference device (high-T, SQUID). To create this system, we used one oscillator as an AC bias controller to operate a multichannel high-T(c) SQUID. To optimize the SQUID parameters (such as the AC bias, offset voltage), two new control sequences based on a cross-correlation method and a fast Fourier transform method were developed. Using the AC bias controller and the sequences, the typical white noise level of the SQUID was about 50-60fTHz(-1/2) around 100Hz. Multichannel MCG signals were detected clearly in the system with the SQUIDs. We conclude that our control system with one oscillator and new protocols can reliably operate a multichannel SQUID.
  • MOS構造を用いた半導体FETガスセンサの水素応答性評価
    後藤康, 横澤宏一, 右高園子, 中野定樹
    電気学会 ケミカルセンサ研究会資料 CHS-05-11 49 - 52 2005年06月 [査読無し][通常論文]
  • A Tsukamoto, K Saitoh, K Yokosawa, D Suzuki, Y Seki, A Kandori, K Tsukada
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15 2 177 - 180 2005年06月 [査読有り][通常論文]
     
    We have constructed a high throughput HTS SQUID fabrication process to develop a 51-channel HTS MCG system. To increase the process throughput of the YBCO deposition, we designed and developed a new deposition system based on a pulsed laser deposition technique. In this deposition system, nine YBCO thin films could be deposited in one deposition sequence by successively depositing the YBCO thin films one by one. In addition to the improvement of the fabrication throughput, the magnetometer pattern was designed to improve the yield of the SQUID fabrication. In our magnetometer design, four SQUIDs were connected with one pickup coil. The yield of good magnetometer chips could be increased by selecting the best SQUID among the four. Using the developed SQUID fabrication process, about one hundred magnetometers were fabricated in a month. The 51-channel HTS MCG system was successfully developed and used for clinical testing.
  • T Kiwa, K Tsukada, M Suzuki, M Tonouchi, S Migitaka, K Yokosawa
    APPLIED PHYSICS LETTERS 86 26 261102  2005年06月 [査読有り][通常論文]
     
    A laser terahertz emission system is proposed to investigate the catalytic metal/semiconductor interfaces of hydrogen sensors. Samples were fabricated by depositing a catalytic metal thin film on a semi-insulating silicon substrate. A femtosecond laser was used to radiate terahertz waves from the sample in a gas cell filled with a hydrogen and nitrogen gas mixture. The peak amplitude of the terahertz waves decreased with increasing hydrogen concentration. We also fabricated a metal-oxide-semiconductor field effect transistor hydrogen sensor, and compared its properties with the terahertz radiation properties. These results suggest that the laser terahertz emission system is a potential tool to investigate catalytic metal/semiconductor interfaces.
  • 無線ネットワークを利用した水素ガス漏洩検知システム
    横澤宏一, 後藤康, 右高園子, 中野定樹, 渡辺篤雄, 嘉本大五郎, 塚田啓二, 紀和利彦
    燃料電池 4 4 60 - 64 2005年04月 [査読無し][招待有り]
  • T. Kiwa, K. Tsukada, M. Suzuki, M. Tonouchi, S. Migitaka, K. Yokosawa
    Optics InfoBase Conference Papers 2005年 
    Terahertz emission properties of catalytic-metal/semiconductor structures under hydrogen gas were investigated for non-contact and non-destructive test of hydrogen sensors. The peak amplitude of terahertz from the samples decreases with increasing the hydrogen concentration.©2005 Optical Society of America.
  • T Kiwa, K Tsukada, M Suzuki, M Tonouchi, S Migitaka, K Yokosawa
    Transducers '05, Digest of Technical Papers, Vols 1 and 2 263 - 266 2005年 [査読有り][通常論文]
     
    Laser terahertz (THz) emission and detection system for investigating catalytic metal/semiconductor interface of the hydrogen sensors was proposed and developed. THz radiation from palladium/silicon structures was successfully obtained. The proper-ties of THz radiation under hydrogen and nitrogen gas mixture were investigated. The peak amplitude of THz radiation was decreased by increasing the volume concentration of hydrogen gas. This change in the amplitude can be explained by change in the local field near the surface of silicon. This result indicates that the system is one of potential tool for non-destructive and non-contact measurement of the hydrogen sensors.
  • S Nakano, Y Goto, K Yokosawa, K Tsukada
    2005 IEEE SENSORS, VOLS 1 AND 2 159 - 162 2005年 [査読有り][通常論文]
     
    We fabricated a prototype for detecting hydrogen gas leaks in hydrogen filling stations. The prototype is composed of a wireless network with ten sensor nodes that can monitor the spatial distribution of hydrogen gas leakage. To enable each sensor node to be driven by a battery, field-effect-transistor sensors and a microprocessor with low power consumption have been adopted. Additionally, a function to consume minimal levels of power has been developed and installed in the microprocessor in each node. The use of batteries and wireless communications enables the nodes to be placed at optimal sensing locations without regard to the wiring needed with existing gas sensors.
  • D Suzuki, A Tsukamoto, K Yokosawa, A Kandori, K Ogata, K Tsukada
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 43 1 117 - 120 2004年01月 [査読有り][通常論文]
     
    A high-temperature superconducting (HTS) magnetocardiographic system composed of 16-channels HTS-Superconducting Quantum Interference Device (SQUID) magnetometers and a vertical magnetically shielded cylinder has been developed. The cylinder is designed to save space and provide mobility for the entire system, including the magnetically shielded cylinder. It consists of two fixed semicircular shells and a sliding semicircular door, all of which are made from sheets of a flexible nanocrystalline soft-magnetic material. The cardiomagnetic field from a subject seated in the vertical magnetically shielded cylinder is measured by multichannel HTS-SQUID magnetometers that are sensitive to field strengths weaker than 100fT/ (Hz)(1/2). The high signal-to-noise ratio of the magnetometer signals makes beat-to-beat measurement of the cardiomagnetic field possible. This HTS-based multichannel MCG system is being applied to medical applications such as the detection of arrhythmias and ischemic heart disease.
  • A Tsukamoto, K Saitoh, K Takagi, K Yokosawa, D Suzuki, K Ogata, T Miyashita, A Kandori, K Tsukada
    APPLIED PHYSICS LETTERS 83 24 5080 - 5082 2003年12月 [査読有り][通常論文]
     
    An electronic first-order gradiometer in a cylindrical magnetic shield was investigated in order to determine the best magnetometer configuration for a compact multichannel magnetocardiograph (MCG). It was found that a planar gradiometer is better in terms of noise reduction than an axial gradiometer. This is because the magnetic field inside the cylindrical magnetic shield exhibits an anisotropic distribution, which was confirmed by a numerical calculation using a three-dimensional finite element method. It was also found that MCG measurement in the cylindrical magnetic shield is possible by using a planar electronic gradiometer with high-T-c directly coupled magnetometers. This configuration can successfully detect the P-wave in MCG signal without the need for averaging. (C) 2003 American Institute of Physics.
  • Koichi Yokosawa, Akira Tsukamoto, Daisuke Suzuki, Akihiko Kandori, Tsuyoshi Miyashita, Kuniomi Ogata, Yusuke Seki, Keiji Tsukada
    Superconductor Science and Technology 16 12 1383 - 1386 2003年12月 [査読有り][通常論文]
     
    A compact, light and easy-to-handle magnetocardiograph (MCG) has been developed. The MCG consists of a sensor array with superconducting-quantum-interference-device magnetometers made of a high-critical temperature superconductor, arranged in a 4 × 4 matrix, and operated in a vertical magnetically shielding cylinder (1.7 m high and 1 m in diameter). Each magnetometer is paired with each of its adjacent magnetometers, and the difference between the respective outputs provides us with a measure of magnetic gradient. This configuration for the electronic gradiometers cancels out the environmental magnetic field noise within the shielding cylinder. We use the data from the multiple gradiometers to construct a current arrow map that describes the distribution of original current vectors in the area being measured. We used the fabricated MCG to record magnetocardiograms of healthy volunteers. The smallest signals, i.e., the P-waves, were clearly detected without averaging. The current arrow maps obtained from the single-beat magnetocardiograms indicate the feasibility of clinical application of this MCG.
  • K. Yokosawa, A. Kandori, T. Miyashita, D. Suzuki, K. Tsukada, A. Tsukamoto
    Appl. Phys. Lett 82 26 4833 - 4835 2003年06月 [査読有り][通常論文]
     
    A magnetocardiograph, consisting of superconducting quantum interference device (SQUID) magnetometers made of a high-critical-temperature (T-c) superconductor and a compact magnetically shielding cylinder, has been developed. We assembled a sensor array of 4x4-matrix-arranged magnetometers which are treated as 24 electronic first-order gradiometers by taking the differences between the outputs in every pair of adjacent magnetometers. Field gradients generated by P waves were estimated from the results for 21 subjects of a conventional magnetocardiograph made of low-T-c SQUID gradiometers. Every gradiometer of the assembled sensor array was then designed to be sufficiently sensitive to detect the field gradient corresponding to the mean P wave. The clear magnetocardiograms obtained without averaging indicate the clinical applicability of the developed magnetocardiograph. (C) 2003 American Institute of Physics.
  • A Kandori, A Tsukamoto, D Suzuki, K Ogata, Y Soutome, T Miyashita, Y Seki, K Yokosawa, K Tsukuda, K Takagi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 13 2 393 - 396 2003年06月 [査読有り][通常論文]
     
    A high-T-c superconducting quantum interference device (SQUID) magnetometer-in which a room-temperature pickup coil is used to detect an impedance magnetocardiogram (I-MCG) signal-has been developed. The pickup coil (30-mm diameter) is installed outside the cryostat and is connected to the input coil of the high-T-C SQUID. The magnetometer's noise level is is 150 fT Hz(-1/2) (> 10 kHz). The magnetometer was used to measure I-MCG signals (about 12 PT), which were obtained by applying an ac current (15 kHz) of constant amplitude (7 mA, peak-to-peak) to a healthy male subject.
  • K. Yokosawa, D. Suzuki, K. Tsukada, A. Tsukamoto
    IEEE Trans. Appl. Supercond 13 2 727 - 730 2003年06月 [査読有り][通常論文]
     
    We have developed a planar gradiometric device with two orthogonal SQUID gradiometers integrated on a substrate. in developing this new device, both series- and parallel-type gradiometric SQUID's (without pickup coils) suitable for the same pickup coils were fabricated. The parasitic inductance, parasitic areas, and cross talks of each SQUID were evaluated to compare their performances. Next, to evaluate the effects of changing field on the SQUID's, the critical current reduction and noise increase under an applied magnetic field were measured. These results show that the parallel SQUID is superior to the series SQUID; thus the parallel SQUID was chosen for use in the new single-chip gradiometric device.
  • K Yokosawa, A Kandori, T Miyashita, D Suzuki, K Tsukada, A Tsukamoto
    APPLIED PHYSICS LETTERS 82 18 3059 - 3061 2003年05月 [査読有り][通常論文]
     
    A stabilizer for superconducting quantum interference device (SQUID) magnetometers operating in lightly shielded environments is proposed. When the stabilizer is applied in an electrical gradiometer, which operates by obtaining differences between the outputs of the two SQUID magnetometers, the intrinsic noise of the stabilizer can be neglected. The operation of an electrical gradiometer where the SQUID magnetometers are of the high-critical-temperature (high-T-c) type is shown to be substantially more stable in a lightly magnetically shielding cylinder with the addition of the stabilizer function. Very clear magnetocardiograms were obtained by a gradiometer of this type. (C) 2003 American Institute of Physics.
  • SQUID（超伝導量子干渉素子）磁束計と心臓磁場計測への応用
    横澤宏一, 塚本晃, 鈴木大介, 神鳥明彦, 宮下豪, 緒方邦臣, 関悠介, 塚田啓二
    日本応用磁気学会研究会 129回研究会資料 47 - 54 2003年03月 [査読無し][招待有り]
  • K Yokosawa, D Suzuki, K Tsukada, A Tsukamoto
    JOURNAL OF APPLIED PHYSICS 92 11 6857 - 6861 2002年12月 [査読有り][通常論文]
     
    A planar gradiometric device for estimating current vectors in specimens, was fabricated as two orthogonal magnetic field gradiometers integrated on a 14.5-mm-square substrate. The gradiometers consist of superconducting quantum interference devices (SQUIDs) and pickup coils made from a low-critical-temperature superconductor. The two gradiometers (one for the x direction and one for the y direction) have exactly the same structure, and their gradiometric centers coincide at the center of the substrate. The gradiometric balance of each gradiometer is 1/2000-1/3700, the cross-talk ratio between the two gradiometers is less than 1% below a few hundred hertz, and their intrinsic noise is 2-3 pT/(mrootHz). The gradiometric configurations of both the pickup coils and the SQUIDs provide good gradiometric balance. The parallel-type gradiometric SQUIDs produced a simple yet effective structure, although the superconducting loops of such SQUIDs have conventionally been thought to lead to adverse effects in the presence of a changing magnetic field. Magnetic fields up to 1 mT, i.e., 20 times the geomagnetic field, applied to a zero-field cooled SQUID reduced the critical current, but did not affect the intrinsic noise. This result shows that the configuration of the SQUIDs kept the circulating current in the superconducting loop away from the Josephson junctions. (C) 2002 American Institute of Physics.
  • 横澤宏一, 鈴木大介, 塚田啓二, 塚本晃
    電子情報通信学会技術研究報告 SCE2002-20 221 19 - 22 一般社団法人電子情報通信学会 2002年07月 [査読無し][通常論文]
     
    基板上に2つのLow-Tc SQUIDグラジオメータを薄膜一体形成したデバイスを試作した。直交2方向の磁場勾配を同時に計測し、直下の電流源を直接推定できる。検出コイルだけでなく、SQUIDも並列型の空間差分構造を持つ。並列型の空間差分SQUIDは磁場の変動に弱いとされるが、1mT(地磁気の20倍)の磁場を加えても固有雑音の上昇がなく、環境磁場の変動に対して安定であることが確認できた。また、試作したデバイスの基本パラメータ(コイルバランス、相互干渉、固有雑音)を実験評価し、実用上十分な性能を有することを確認した。
  • A Kandori, T Miyashita, D Suzuki, K Yokosawa, K Tsukada
    IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING 49 7 721 - 728 2002年07月 [査読有り][通常論文]
     
    A new method for measuring two-dimensional (2-D) impedance magnetocardiograms (I-MCGs) and magnetocardiograms (MCGs) above the heart simultaneously, has been developed. The I-MCG's and MCG's signals are recorded by using a superconducting interference device (SQUID) system. To measure the I-MCG and MCG signals, four first-order gradiometers with an 18-mm, diameter and a 50-mm baseline were used. The SQUIDs are driven by a flux-locked-loop circuit with a frequency range higher than that of an ac-current (40 kHz) with constant amplitude passed through a subject. The output of the circuit is filtered through two circuits: one for measuring the I-MCG signals and one for measuring the MCG signals. The I-MCG signals are obtained by demodulating the magnetic field, which is detected by the gradiometers, at the frequency of the ac current. As a result, the I-MCG signal reflects the change in spatial distribution of conductivity caused by the movement of the heart muscle and blood volume. A contour map of the 2-D I-MCG signals showed the largest signals occur above the right ventricle and right atrium. In a corresponding current-arrow map, it was found that the large current arrows occurred above the right side of the right ventricle. Furthermore, it was found that the systole and diastole timings obtained from the first-derivative I-MCG signal and the phonocardiogram were different. These results show that primitive 2-D I-MCG signal can provide much physiological information on the circulatory movement of the heart.
  • A Tsukamoto, K Yokosawa, T Fukazawa, D Suzuki, K Tsukada, T Miyashita, A Kandori, K Takagi
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 368 1-4 41 - 44 2002年03月 [査読有り][通常論文]
     
    We have fabricated a first-order, directly coupled gradiometer with a gradiometric balance below 0.1% without balance adjustment by selecting the coupling direction of the pickup coil and the superconducting quantum interference device. The noise of the gradiometers with various balances measured in an unshielded environment decreased in proportion to the improvement in balance. However, the noise of the gradiometer with a balance of 0.03% was limited by the gradient field component of the environmental noise. Magnetocardiogram measurement with this gradiometer in an unshielded environment was also demonstrated. (C) 2001 Elsevier Science B.V. All rights reserved.
  • S Kuriki, H Oyama, A Hayashi, S Hirano, T Washio, M Matsuda, K Yokosawa
    IEICE TRANSACTIONS ON ELECTRONICS E85C 3 670 - 676 2002年03月 [査読有り][通常論文]
     
    We describe here development of a multichannel high-Tc SQUID magnetometer system for measurement of cardiac magnetic fields, aiming at future application of diagnosis of heart diseases. Two types of direct-coupled SQUID magnetometers were fabricated and used: single pickup coil magnetometer having flux dams to suppress the shielding current that would induce flux penetration and the consequent low-frequency noise, and double pickup coil magnetometer having no grain boundary junctions and flux dams on the pickup coil. The superconducting film of both the magnetometers had holes and slots, leaving 5 mum-Aide strip lines, to suppress trapping and penetration of magnetic flux vortices in environmental fields. We studied different schemes of active shielding to reinforce the efficiency of field-attenuation of magnetically shielded room (MSR). A feedback-type compensation using a normal detection coil wound around the wall of MSR and a selective cancellation of 50 Hz noise by means of adaptive filter were developed, Such combination of passive and active shielding, based on the use of simple MSR, would be suitable in a practical low-cost magnetometer system for clinical MCG examination. We fabricated a liquid nitrogen cryostat that could contain up to 20 magnetometer-capsules at 4cm separation in a flat bottom, with a distance of 16 mm between the air and liquid nitrogen. The cryostat was set in a gantry, which had rotational, vertical and horizontal freedoms of movement, in a moderate-shielding MSR that was combined with the developed active shielding. Measurements of MCG were performed for normal subject using eight magnetometers operating simultaneously.
  • A Kandori, D Suzuki, K Yokosawa, A Tsukamoto, T Miyashita, K Tsukada, K Takagi
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 2A 596 - 599 2002年02月 [査読有り][通常論文]
     
    To measure an impedance magnetocardiogram (I-MCG) signal, we have developed a superconducting quantum interference device (SQUID) magnetometer with a room-temperature pickup coil. The pickup coil (30-mm diameter) is set outside the cryostat and is connected to the input coil in the SQUID. The noise level of the magnetometer is 90 fT Hz(-1/2) at 10 kHz. Using the magnetometer, we measured I-MCG signals (below 15 pT)-which were obtained by applying an ac current (10 kHz) with constant amplitude (7 mA, peak-to-peak) to a subject-from the heart.
  • K Yokosawa, A Tsukamoto, T Miyashita, A Kandori, D Suzuki, K Tsukada, K Takagi
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 15 1 136 - 140 2002年01月 [査読有り][通常論文]
     
    To design practical planar high-T-c SQUID gradiometers for magnetocardiographs, a signal-to-noise (S/N) chart that will enable the gradiometers to detect P-waves was developed. The signal was estimated as the gradient field generated by the mean current dipole of P-waves of 20 healthy volunteers. The current dipoles were obtained by using a conventional magnetocardiograph comprising low-T-c SQUID gradiometers. On the other hand, the noise was estimated from studies on previously reported gradiometers based on the limit of intrinsic gradient field noise. The obtained S/N chart indicates that a gradiometer with a baseline longer than 12 mm is necessary for detecting P-waves without averaging. The reliability of the S/N chart was confirmed by detecting actual P-waves with 100-beat averaging by using a fabricated planar high-T-c SQUID gradiometer with a baseline of 6.75 mm.
  • A Tsukamoto, T Fukazawa, K Takagi, K Yokosawa, D Suzuki, K Tsukada
    APPLIED PHYSICS LETTERS 79 26 4405 - 4407 2001年12月 [査読有り][通常論文]
     
    We fabricated directly coupled gradiometers made of YBa2Cu3Oy thin films on bicrystal substrates. The parasitic effective area of the gradiometric pickup coil was found to be comparable with that of the superconducting quantum interference devices (SQUIDs) in each gradiometer. A gradiometer balance of below 10(-3) was achieved by selecting the coupling direction of the SQUID so as to cancel the parasitic effective area of the pickup coil by the effective area of the SQUID itself. The noise of the gradiometers measured in an unshielded environment decreased in proportion to the improvement in the gradiometer balance; however, the noise of the gradiometer with a balance of 0.03% was limited by the gradient-field component of the environmental noise. (C) 2001 American Institute of Physics.
  • D Suzuki, K Yokosawa, T Miyashita, A Kandori, K Tsukada, A Tsukamoto, S Arakawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 40 10A L1026 - L1028 2001年10月 [査読有り][通常論文]
     
    A small and simple magnetic-shielding cylinder using a new high-permeability sheet, developed for magnetic shielding, can reduce the amount of effort expended on taking magnetocardiogram (MCG) measurements. This sheet is made of a nanocrystalline soft-magnetic material (an Fe-Cu-Nb-Si-B alloy) and is flexible and easy to handle. Moreover, magnetostriction of the material is nearly zero, unlike that of the materials used in conventional magnetic shielding. The shielding cylinder is made up of three tubes of various diameters (but having the same length), placed one inside the other. The shielding cylinder is 1.0 m in diameter and 2.0 m long, and it has a shielding factor of about 35 dB at 1 Hz. The shielding cylinder was tested by measuring MCGs using a high-T-c superconducting quantum interference device (SQUID) gradiometer.
  • Measurement of Two-dimensional Impedance Magnetocardiogram –Model Experiment-
    A. Kandori, D. Suzuki, T. Miyashita, K. Yokosawa, K. Tsukada
    EEE/EMBS 4 25 - 28 2001年10月 [査読有り][通常論文]
  • K Yokosawa, S Kuriki, S Hirano, H Oyama, D Suzuki, K Tsukada
    JOURNAL OF APPLIED PHYSICS 90 8 4049 - 4055 2001年10月 [査読有り][通常論文]
     
    We have investigated the behavior of high-critical-temperature (high T-c) direct-coupled superconducting quantum interference device (SQUID) magnetometers in static and fluctuating magnetic fields. The magnetometers consist of narrow-linewidth superconducting films to prevent flux trap during field cooling. Moreover, they have no superconducting films crossing the bicrystal lines of the substrates (except at the Josephson junctions); i.e., they have no flux dams. When one of these magnetometers was cooled in a static magnetic field B-cool, the low-frequency noise when B-cool< 100 <mu>T was as low as that under zero-field cooling, but above 100 muT the noise increased substantially. On the other hand, when a field B-ext of less than 4 muT was applied after zero-field cooling, the low-frequency noise increased in proportion to B-ext. It returned to its original value reversibly when B-ext was turned off. However, when B-ext was greater than or equal to 4 muT, the output of the flux-locked-loop started to drift with time and the low-frequency noise increased further. This additional noise increase remained after turning off B-ext. These results suggested that there are two modes of increase for the low-frequency noise induced by flux penetration due to the shielding current: a "reversible" mode and an "irreversible" mode. We found that the low-frequency noises of the two modes were additive with respect to their power, suggesting that the two noises derived from independent sources at different sites on the magnetometer. We also found that the reversible-mode noise could be reduced by improving the profile of the film edge. (C) 2001 American Institute of Physics.
  • K Yokosawa, H Oyama, S Kuriki, D Suzuki, K Tsukada
    APPLIED PHYSICS LETTERS 78 18 2745 - 2747 2001年04月 [査読有り][通常論文]
     
    A first-order axial gradiometer has been constructed using two high-critical-temperature superconducting-quantum-interference-device magnetometers having a double-pickup loop configuration on bicrystal substrates. The magnetometer, which had a slot-type structure but no weak links on the pickup loops, can be operated steadily in an unshielded environment after in situ cooling. The gradiometer was formed by connecting the feedback and the compensation coils of the two magnetometers in series using a normal conductive wire. Sufficiently high noise reduction (31 dB at 1 Hz) was achieved without any need for adjustments and low-noise magnetocardiograms were obtained with the gradiometer in a moderately magnetically shielded room. (C) 2001 American Institute of Physics.
  • K Yokosawa, H Oyama, S Kuriki, D Suzuki, K Tsukada, M Matsuda
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 11 1 1335 - 1338 2001年03月 [査読有り][通常論文]
     
    A direct-coupling-type high-critical-temperature (high-T-c) SQUID magnetometer with two pickup loops per SQUID on a bicrystal substrate has been fabricated. To avoid flux trapping, the superconducting films of the pickup loops have slits with a separation of 5 mum To suppress flux entry into the pickup loops, there are no weak links on the pickup loops, ie., no flux dams, In field Fooling, noise did not substantially increase in low frequency region unless the Field reached around 100 muT Regardless of whether the magnetometer was previously zero-field-cooled or field-cooled, the flux did not enter the pickup loop until the changing field exceeded about 10 muT The magnetometer cooled under the geomagnetic- and environmental-field noise could work in an unshielded environment. A gradiometer was made by connecting the feedback coils of two magnetometers in series. The environmental field noise was reduced by the gradiometer by about 35 dB,
  • M Matsuda, S Ono, K Kato, T Matsuura, H Oyama, A Hayashi, S Hirano, S Kuriki, K Yokosawa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 11 1 1323 - 1326 2001年03月 [査読有り][通常論文]
     
    We have fabricated and characterized high-T-c planar SQUID magnetometers and first derivative gradiometers with directly-coupled pickup loops. The devices were made from single layer of YBa2Cu3O7-8 thin film on LSAT bicrystal substrate with 30 degrees or 24 degrees misorientation angle, Magnetic properties were investigated by applying a magnetic field Bo for the SQUID magnetometer patterned with holes to reduce the maximum structural width. We found an increasing Low frequency noise with cooling fields B-0 larger than 1.5 muT This value consists with the threshold field estimated from the maximum structural width. A magnetic field noise level of 500 fT/Hz(1/2) at 10 Hz was observed by using PLL electronics with a bias current reversal in a moderate magnetically-shielded room consisting of only two 1mm thick layers of permalloy, Measurements of magnetocardiograms demonstrate the suitability of this magnetometer for biomagnetic applications. On the other hand, the gradiometer with two symmetric pickup loops was operated without any shielding. The performance obtained was a field gradient resolution of about 1 pT/cmHz(1/2) at 1 kHz and 10 pT/cmHz(1/2) at 1 Hz, with a baseline of 4 mm, The imbalance of this gradiometer was around 0.7%, limited by the sensitivity to homogeneous field of the SQUID itself.
  • A Kandori, T Miyashita, D Suzuki, K Yokosawa, K Tsukada
    PHYSICS IN MEDICINE AND BIOLOGY 46 2 N45 - N48 2001年02月 [査読有り][通常論文]
     
    We have developed an impedance magnetocardiogram (IMCG) system to detect the change of magnetic field corresponding to changes in blood volume in the heart. A low magnetic field from the electrical activity of the human heart-the so-called magnetocardiogram (MCG)-can be simultaneously detected by using this system. Because the mechanical and electrical functions in the heart can be monitored by non-invasive and non-contact measurements, it is easy to observe the cardiovascular functions from an accurate sensor position. This system uses a technique to demodulate induced current in a subject. A flux-locked circuit of a superconducting quantum interference device has a wide frequency range (above 1 MHz) because a constant current (40 kHz) is fed through the subject. It is shown for the first time that the system could measure IMCG signals at the same time as MCG signals.
  • K Yokosawa, D Suzuki, A Tsukamoto, T Miyashita, A Kandori, K Tsukada, K Takagi
    PROCEEDINGS OF THE 23RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-4 23 3281 - 3284 2001年 [査読有り][通常論文]
     
    A magnetocardiograph (MCG), which consists of a sensor comprising four superconducting-quantum-interference device (SQUID) gradiometers and a magnetic shielding cylinder made of nanocrystalline soft magnetic materials, has been developed. The sensor can be handled easily because the gradiometers are made of high-critical-temperature (Tc) superconductor operated in liquid nitrogen. Further, the shielding cylinder is lightweight (160 kg) and compact (2 in long and 1 m in diameter). The gradiometer balance is high enough (typically 0.1%) for recording magnetocardiograms inside the shielding cylinder, whose shielding factor is -35 dB at 1 Hz. We used the new MCG to record magnetocardiograms of a healthy volunteer at four different positions. From this magnetocardiograms we then obtained a current arrow map, by which mycardium activity can be estimated, at 16 sites (4 x 4 matrix) on the measurement plane. The similarity between the current-arrow map obtained by a conventional MCG and that from the newly developed MCG indicates that the developed compact MCG is also capable of estimating the region of cardiac activity.
  • A Kandori, D Suzuki, T Miyashita, K Yokosawa, K Tsukada
    PROCEEDINGS OF THE 23RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-4 23 374 - 377 2001年 [査読有り][通常論文]
     
    The purpose of this paper is to clarify the relationship between impedance magnetocardiogram (I-MCG) signal and its source position. We measured I-MCG signals that could be obtained above a heart two-dimensionally by inducing a current with high frequency. To record the signals, we used a superconducting interference device (SQUID) that was connected to a pickup coil of first-order-gradiometer type. To ensure the source of I-MCG signals, we measured magnetic field changing to the movement of rubber balloon in water tab. The magnetic field of the balloon model could be obtained around the balloon shape. In comparison between the I-MCG signals and the result of balloon model, the I-MCG signals have the information due to changes of electrical conductivity in a heart. Furthermore, it can be thought that the peak position of I-MCG signals might slightly be different from that of electrical conductivity change.
  • 小山 洋, 栗城 眞也, 横澤 宏一
    電子情報通信学会論文誌. C, エレクトロニクス 83 9 860 - 866 一般社団法人電子情報通信学会 2000年09月25日 [査読無し][通常論文]
     
    YBa_2Cu_3O_<7-x>(YBCO)薄膜中への磁束トラップを抑制するため, 数μm幅のYBCOストリップからなるメッシュ状のSQUID磁束計を設計, 試作した.また, 遮へい電流による磁束トラップを抑える目的で, 検出コイルに弱結合(フラックスダム)を作り込んだ.10μTを超える磁場中で素子を冷却した場合, V-φ特性に磁束シフトが観測されたことから, 約10μTをしきい値として磁束トラップが生じたと推定された.このしきい値は弱結合部近傍のYBCO薄膜の幅から計算される値に対応する.ゼロ磁場冷却後に磁場を印加すると, 遮へい電流によるフラックスダムが電圧状態となり, 検出コイル内に磁束が侵入した.そのしきい値磁場は0.14μTであり, 推定された臨界電流値は0.5mAであった.印加磁場に対するフラックスダムの臨界電流の変化はフラウンホーファー的な特性を示し, 電流値が極小となる磁場の値から印加した磁束が弱結合部に集中する機構があると推測された.
  • K Yokosawa, D Suzuki, K Tsukada, S Ugai, T Suzuki, Y Shimizu
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 13 8 1286 - 1291 2000年08月 [査読有り][通常論文]
     
    We have fabricated low-T-c SQUIDs (superconducting quantum interference devices) that have a built-in heater module next to the Josephson junctions to remove trapped Aux by using only a low heating power. To suppress the generation of magnetic fields, the heater module comprises a double-layer consisting of a heater, which is a narrow Nb film, and an Al electrode. The module can be fabricated together with the SQUID without complicating the process. The Nb heater is transformed to normal metal with sufficient resistance when a current above the critical current flows through it. We demonstrated that the heater module could reliably remove trapped flux with 24 mW without increasing any noise of the SQUID or causing re-trapping.
  • K Yokosawa, K Sasaki, S Umemura, R Shinomura, S Ishikawa, S Sano, Y Ito
    ULTRASOUND IN MEDICINE AND BIOLOGY 26 4 503 - 507 2000年05月 [査読有り][通常論文]
     
    Intraoperative diagnostic tissue differentiation is expected to be useful clinically. We have fabricated a 3-mm diameter rod-shaped ultrasound (US) probe mounted with a 120-MHz transducer whose lateral resolution is the same as the cellular size of 13 mu m. The probe can image a microscopic structure (i.e., the cellular arrangement inside intracorporeal living tissue). We imaged normal kidney tissue of a living mouse and tumor tissue implanted in another mouse kidney, We anesthetized the mice, exteriorized the kidneys, and punctured the kidneys with the probe, Renal corpuscle-like structures were seen in the healthy kidney, but a wavy spindle-like structure was seen in the tumor. The similarity between the ultrasonic images and histological sections taken from the imaged organs demonstrates the possibility of real-time tissue differentiation by ultra-high-frequency US. (C) 2000 World Federation for Ultrasound in Medicine & Biology.
  • K Yokosawa, K Sasaki, S Umemura, R Shinomura, S Ishikawa, S Sano, Y Ito
    ULTRASOUND IN MEDICINE AND BIOLOGY 26 4 503 - 507 2000年05月 [査読有り][通常論文]
     
    Intraoperative diagnostic tissue differentiation is expected to be useful clinically. We have fabricated a 3-mm diameter rod-shaped ultrasound (US) probe mounted with a 120-MHz transducer whose lateral resolution is the same as the cellular size of 13 mu m. The probe can image a microscopic structure (i.e., the cellular arrangement inside intracorporeal living tissue). We imaged normal kidney tissue of a living mouse and tumor tissue implanted in another mouse kidney, We anesthetized the mice, exteriorized the kidneys, and punctured the kidneys with the probe, Renal corpuscle-like structures were seen in the healthy kidney, but a wavy spindle-like structure was seen in the tumor. The similarity between the ultrasonic images and histological sections taken from the imaged organs demonstrates the possibility of real-time tissue differentiation by ultra-high-frequency US. (C) 2000 World Federation for Ultrasound in Medicine & Biology.
  • K. Yokosawa, H. Oyama, S. Kuriki, D. Suzuki, K. Tsukada
    Physica C: Superconductivity and its Applications 341-348 Pt.4 2705 - 2706 2000年 [査読有り][通常論文]
     
    A direct-coupling-type high-Tc SQUID magnetometer with two pickup loops per SQUID on a substrate has been fabricated. To suppress the flux trapping and vortex entry, the superconducting film of the whole device except a 5-μm-wide transmission-line-shaped SQUID is composed of narrow (5 μm) lines with slots and holes. The threshold field for the flux trapping during field cooling was evaluated to be around 130 μT, a much larger field than the geomagnetic field. Moreover, applying a field after cooling reduced the critical current of the SQUID to zero at 6 μT. And vortex entry into the pickup loop occurred at a field exceeding about 10 μT.
  • H Oyama, K Yokosawa, M Matsuda, S Kuriki
    ADVANCES IN SUPERCONDUCTIVITY XII 1027 - 1029 2000年 [査読有り][通常論文]
     
    In order to suppress the flux entry into YBa2Cu3O7-x (YBCO) thin film of dc-SQUIDs, we have designed and fabricated SQUID magnetometers with a mesh structure having slots and holes. The magnetometer also included flux dams within the pickup loop to suppress the flux entry driven by shielding current. In the field cooling, we observed a flux shift caused by flux trapping in the V-Phi characteristics above 10 mu T, which agreed with the calculated value from the width of the YBCO film near the flux dam. When the applied field changed above 0.14 mu T, the flux dams opened and the flux entered into the pickup loop. The critical current of the flux dams decreased with the applied field in a Fraunhofer-like pattern.
  • 小山 洋, 平野 悟, 横澤 宏一, 松田 瑞史, 栗城 眞也
    電子情報通信学会技術研究報告. SCE, 超伝導エレクトロニクス 99 408 7 - 12 一般社団法人電子情報通信学会 1999年10月29日 [査読無し][通常論文]
     
    YBa_2Cu_3O_<7-x>(YBCO)薄膜中への磁束トラップを抑制するためのスロットとホール構造を持つメッシュ状のSQUID磁束計を設計・試作した。また、遮蔽電流による磁束トラップを抑える目的で、検出コイルに弱結合(フラックスダム)を作り込んだ。メッシュを構成するYBCO膜の幅は5μmであるが、弱結合部の近傍では12μmの部分がある。素子を磁場中で冷却した場合、10μTを超えるとV-Φ特性に磁束シフトが起きたことから、10μTを閾値として磁束トラップが生じたと推定された。この閾値は弱結合部近傍の幅に対応する。フラックスダムが電圧状態になり検出コイル内に磁束が侵入しはじめる磁場は0.14μTであり、その時の推定臨界電流値は0.5mAであった。印加磁場に対するフラックスダムの臨界電流の変化を調べたところ、フラウンフォーファー的な特性を示し、電流値が極小となる磁場の値から印加磁束が弱結合部に集中する機構があると推測された。
  • K Yokosawa, E Maruyama, RS Ahmad, H Oyama, S Kuriki, D Suzuki, M Koyanagi
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 37 8 4362 - 4366 1998年08月 [査読有り][通常論文]
     
    We propose a new configuration for direct-coupling-type high-T-c superconducting quantum interference device (SQUID) magnetometers consisting of two pickup coils per SQUID on a bicrystal substrate. The SQUID and pickup coils can be arranged symmetrically without covering the bicrystal line on the substrate. This configuration should produce a large coupling coefficient from the pickup coil to the SQUID, and thus a large effective pickup area. First, we optimized the structure and dimensions of the pickup coils using an analogous model made of normal metal. Second, we fabricated SQUIDS for this configuration, in which the slitlike holes were located parallel to the bicrystal line. We also fabricated magnetometers consisting of pickup coils and SQUIDs of this configuration from YBCO film on bicrystal 10 mm x 10 mm SrTiO3 substrates. An effective area of 0.42 mm(2) has been achieved, which was measured by applying an external magnetic field.
  • 丸山 恵美, 横澤 宏一, Ahmad Rashdi Shah, 栗城 眞也, 鈴木 大介, 小柳 正男
    電子情報通信学会技術研究報告. SCE, 超伝導エレクトロニクス 98 222 7 - 12 一般社団法人電子情報通信学会 1998年07月28日 [査読無し][通常論文]
     
    直結型高温超伝導SQUID磁束計の検出コイルとSQUID間の磁気結合度を調べるため、形状の異なるSQUIDを作製し、外部から電流を流すことによってSQUIDに磁気結合するインダクタンス成分を実験的に求めた。その結果、検出コイルからの電流が複雑な経路をとる形状ほど磁気結合度は劣ること、ストリップが細く、電流密度が偏在しない形状では磁気結合度は向上することがわかった。また、平行線状のSQUIDでは、SQUID外部の導入部の電流による磁束結合の効果も見られた。
  • E Maruyama, S Kuriki, K Yokosawa, RS Ahmad, D Suzuki, M Koyanagi
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 37 6B L722 - L724 1998年06月 [査読有り][通常論文]
     
    We have fabricated high-T-c dc superconducting quantum interference devices (SQUIDs), which have different geometries of the hole and configurations of current injection leads, in the direct-coupling magnetometer, and measured the coupling efficiency of the flux generated by the injected current. It has been found that the coupling is efficient in the case where the current flows uniformly across the width of the path around the SQUID hole. High coupling of more than 80% was obtained in a geometry of narrow parallel strips with wide slit of the SQUlD hole between them.
  • 横澤 宏一, Ahmad Rashdi Shah, 丸山 恵美, 栗城 真也, 鈴木 大介, 小柳 正男
    電子情報通信学会技術研究報告. SCE, 超伝導エレクトロニクス 97 219 25 - 30 一般社団法人電子情報通信学会 1997年07月30日 [査読無し][通常論文]
     
    Direct-coupling型HTc-SQUID磁束計として, 基板面積を2分割する2つの検出コイルを持つDouble pickup-coil磁束計を提案した. さらに, この磁束計の検出コイルとSQUIDについて, その適切な形状を実験的に検討した. 検出コイルについては, 検出コイルのモデルを常伝導金属膜で製作してその自己インダクタンスを計測する実験を行い, 検出コイルからSQUIDへの磁束伝達効率が最大となる検出コイル形状を決定した. また, SQUIDについては縦型(Longitudinal)SQUIDと, 横型(Transverse)SQUIDの双方を試作し, その性能を比較した. 双方で規格化された電圧振幅に差はなく, 横型SQUIDのほうが検出コイルとの磁気結合が良好であった.
  • K Yokosawa, Y Ito, S Sano, R Shinomura, Y Sato
    ULTRASONIC TRANSDUCER ENGINEERING 3037 13 - 21 1997年 [査読有り][招待有り]
     
    We have fabricated a miniature 120-MHz transducer for imaging the internal structure of living samples, and mounted it in a 3-mm-diameter rod-shaped probe which ensures contact with a tissue to evaluate the tissue imaging capability of the transducer. The transducer consists of a thin film of 12.5-mu m thick ZnO sandwiched between two metal electrodes, the bottom one deposited on a sapphire substrate whose other face has a polished concave-sphere acoustic lens. Both the lens diameter and the sphere radius are 0.5 mm; that is, the F number of the lens is 1. The lens of the transducer faces outwards in the probe so that the ultrasound can be transmitted and received directly by it in the radial direction of the rod without any mirrors. As the probe rotates mechanically around its axis and shifts in the direction of the axis, a cylindrical plane created by the locus of the beam focus is located inside of the tissue. Using this scanning, we form tissue images in the C-scan mode in a cylindrical plane within the target tissue. Preliminary results for imaging an in vitro bovine kidney sample into which the probe was inserted demonstrate that the fabricated probe can image microscopic structure inside tissue samples.
  • K Yokosawa, R Shinomura, S Sano, Y Ito, S Ishikawa, Y Sato
    ULTRASONIC IMAGING 18 4 231 - 239 1996年10月 [査読有り][通常論文]
     
    Ultrasound transducers with center frequency above 100 MHz are expected to be used for future diagnostic tissue characterization because of their high lateral resolution. We have fabricated a 120-MHz transducer that consists of a ZnO piezoelectric film on a sapphire substrate that has a concave acoustic lens. The lateral resolution was calculated as 13 mu m. The insertion loss of the transducer, defined as the difference between the received voltage and. the transmitted one, was -45 dB. The 6-dB bandwidth of the received signal was approximately 40 MHz. The transducer was mounted in a rod-shaped probe to ensure contact with in vivo tissue, because of the low penetration of ultrasound in the high frequency region. While the probe is rotated and moved along its axis mechanically, the transducer receives backscattered ultrasound from the surrounding tissue on a cylindrical plane that is kept a constant distance from the probe surface. The feasibility of this high-frequency tissue imaging probe has been demonstrated by obtaining preliminary images of an in vitro bovine kidney. (C) 1996 Academic Press.
  • Y Ito, K Yokosawa, S Sano, R Shinomura, Y Sato
    ISAF '96 - PROCEEDINGS OF THE TENTH IEEE INTERNATIONAL SYMPOSIUM ON APPLICATIONS OF FERROELECTRICS, VOLS 1 AND 2 1 83 - 86 1996年 [査読有り][招待有り]
     
    Thin-film ZnO ultrasonic transducers for operation at 140 MHz mounted in a rod-shaped probe were fabricated and evaluated for use in tissue characterization. Highly oriented ZnO films 12.5-mu m thick were successfully grown for use as transducers having sufficient sensitivity to detect small ultrasound signals inside living samples. The ZnO transducer was mounted in the rod-shaped probe which could rotate mechanically around its axis and shift along the axis. Using this scanning, tissue images were formed in the C-scan mode in a cylindrical plane within the tissue. Preliminary bovine kidney images demonstrate the feasibility of tissue imaging using the miniature, high-frequency transducers mounted in the rod-shaped probe.
  • K Yokosawa, S Kuriki
    BIOMAGNETISM: FUNDAMENTAL RESEARCH AND CLINICAL APPLICATIONS 7 510 - 514 1995年 [査読有り][通常論文]
  • K YOKOSAWA, S KURIKI
    REVIEW OF SCIENTIFIC INSTRUMENTS 65 12 3814 - 3819 1994年12月 [査読有り][通常論文]
  • 直結帰還型グラジオメータの雑音解析
    横澤宏一, 栗城眞也
    電気学会 マグネティックス研究会資料 MAG-93-229 41 - 50 1993年11月 [査読無し][通常論文]
  • V-特性を考慮したSQUID磁束計のシミュレーション
    福田恵子, 岡島健一, 神鳥明彦, 横澤宏一, 武田栄里子
    電気学会 マグネティックス研究会資料 MAG-92-229 29 - 36 1992年11月 [査読無し][通常論文]
  • 多チャンネルSQUID磁束計システムの開発
    横澤宏一, 岡島健一, 福田恵子, 神鳥明彦, 武田栄里子
    電気学会 マグネティックス研究会資料 MAG-92-228 19 - 27 1992年11月 [査読無し][通常論文]
  • SQUID磁束計用シミュレータ回路に関する一検討
    福田恵子, 岡島健一, 堀田正生, 横澤宏一, 神鳥明彦
    電気学会 電子回路研究会資料 ECT-92-24 79 - 86 1992年06月 [査読無し][通常論文]
  • S MURAYAMA, K YOKOSAWA, Y MIYAKO, T MATSUZAKI, K NAGAMINE, T YAMAZAKI, EF WASSERMANN
    SOLID STATE COMMUNICATIONS 61 12 755 - 759 1987年03月 [査読有り][通常論文]
  • S MURAYAMA, K YOKOSAWA, Y MIYAKO, EF WASSERMANN
    PHYSICAL REVIEW LETTERS 57 14 1785 - 1788 1986年10月 [査読有り][通常論文]
  • 横澤 宏一
    物性研究 46 4 583 - 584 物性研究刊行会 1986年07月20日 [査読無し][通常論文]
     
    この論文は国立情報学研究所の電子図書館事業により電子化されました。
  • S MURAYAMA, K YOKOSAWA, Y MIYAKO, EF WASSERMANN
    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 54-7 Pt.1 221 - 222 1986年02月 [査読有り][通常論文]
  • S SUDO, S MURAYAMA, K YOKOSAWA, T MIYADAI, Y MIYAKO, Y ITO, K HIRAKAWA
    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 52 1-4 431 - 433 1985年 [査読有り][通常論文]

書籍

  • 柿木 隆介, 横澤 宏一, 栗城 真也 (担当:編者(編著者))
    Hokkaido University Press 2008年 (ISBN: 9784832903555)
  • 水素利用技術集成Vol. 3
    横澤宏一 (担当:分担執筆範囲:高精度水素漏洩検知無線センサシステム)
    （株）エヌ・ティー・エス 2007年
  • 非侵襲・可視化技術ハンドブック-ナノ・バイオ・医療から情報システムまで-
    横澤宏一, 栗城眞也 (担当:分担執筆範囲:脳磁図(MEG)計測システム)
    （株）エヌ・ティー・エス 2007年

その他活動・業績

特許

受賞

  • 2016年09月 日本生体医工学会 ベストリサーチアワード
     Alpha-band amplitude during memory encoding is an index of memory performance 
    受賞者: 横澤宏一
  • 2015年09月 日本生体医工学会 ベストリサーチアワード
     聴覚性定常脳磁界応答の音楽的期待による変調 
    受賞者: 横澤宏一

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年04月 -2026年03月 
    代表者 : 柳生 一自, 齊藤 卓弥, 横澤 宏一, 白石 秀明
     
    私たちは北海道大学にある2台の脳磁計（Magnetoencephalography: MEG）を光ファイバーで接続し、映像・音声での仮想的対面を可能とするDual-MEGシステムを構築した。さらによりリアルな対面を行えるようカメラとプロジェクタの視差をなくすハーフミラーを用い正面からの視線合致を可能とした。このDual-MEGシステムを用いて、実対面（相手の映像と実際に対面している状況）、擬対面（録画された相手の映像と対面している状況）とを用いて、被験者に判断させる課題を行った。結果、本人は擬対面だと答えている（実対面には気付いていない）にも関わらず、右下前頭部におけるθ波の活動が、映像が実対面では脱同期、擬対面では過同期をすることを明らかにした。すなわち意識レベルでは相手の存在に気づいていない（非意識）にも関わらず、「相手の存在」を脳内で表象化する機構が同部位に存在することを示した。さらに考察をすすめこの二条件の違いは、他者との無意識の交互作用にあること、そのやりとりはfacial mimicry（表情模倣）にあることを推論した。こうした点は進化学的見地、発達学的見地からも合理的であると考えられ、トップダウンの認知とは別の、ボトムアップによって他者が象徴化される機構を示しているのかもしれない。こうした中前頭回を中心としたこの非意識下における他者存在の象徴化については統計学的な検討を深めた上で、研究成果については現在論文化を進めている。さらに2021年度は、研究対象として健常者同士によるコミュニケーションモジュールの同定、解析方法としては単一被験者の脳活動におけるモジュール同定を目的とした周波数解析と事象関連同期・脱同期の解析を進めた。熟練した脳磁図計測および解析方法を行える研究協力者が必要であり、育成を進めている。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 大塚 明香, 横澤 宏一, 西本 博則
     
    本研究では, 脳の自発律動, 視聴覚性定常反応, また, 呼吸や心拍／脈拍等の生理律動に関連する生体磁気信号をMEG装置により一元的に検出し, 成分間の周波数比を評価するための手法を開発している. 初年度（2021年度）は, 本手法で指標とする磁界成分の基礎周波数となる心拍／脈拍に関連する心磁界雑音成分について, 生理学的機序と時空間特性を調べた．まず, MEGセンサを被験者の頭部, 頸部, 胸部に近付けた時のMEG信号を計測した. また, 雑音事象の時間基準として, 心電図を同時計測した. 次に, MRI装置により頭部, 頸部, 胸部の構造画像と血管画像（MRA）を撮像し, 各部位の皮膚表面, 脳, 心臓, および, 動静脈の実形状モデルを作成した. 各モデルで定義した信号空間に対して均一の導電率を設定し, 心磁界雑音の電流密度分布を推定した. その結果, 心磁界雑音のピーク潜時は心電図のR波に同期しており, 最大電流密度は心室中隔および左右心室の心筋付近に推定された. 頭蓋内の残差成分は, 椎骨動脈と中大脳動脈に局在した. これらの結果から, 心磁界雑音には心筋細胞の膜電位変化に伴う心室収縮に由来する磁界成分と, 脳血管の脈動に関連する磁界成分が重畳している事が示唆された. 一方で, DC成分の最大電流密度は上矢状洞に推定された. これは, 動脈血の反磁性に対し, 静脈血の常磁性を反映している可能性を示す. 本研究の結果は, 心拍／脈拍成分の正確な抽出を可能にすると共に, 循環器系の非侵襲・非接触な定量的評価法の開発など, MEG活用分野の新規開拓にもつながることが期待される. 以上が本年度の成果である.
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2015年04月 -2019年03月 
    代表者 : 佐藤 華織, 山口 泰彦, 横澤 宏一, 前澤 仁志, 箕輪 和行
     
    歯根膜刺激時の脳活動部位について、脳磁図で記録し、周波数解析及び脳の形態を標準脳形にする手法を用いるStatistical Parametric Mapping(以下SPM8)による信号源解析を行なった。その結果、不快刺激で低下するα律動のパワー値は、刺激OFF時と比較して刺激ON時の方が有意に低い値を示した。SPM信号源解析では、刺激ON、OFF条件ともに頭頂・後頭領域が信号源であることが推定された。しかし、反応強度の差は各条件で観察された部位以外でも認められた。 一方、主観的評価として記録した刺激時のVASとピークパワー値に相関関係がある傾向が観察されたが、更に検討が必要と思われた。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2014年04月 -2016年03月 
    代表者 : 松永 理恵, 阿部 純一, 横澤 宏一, ハルトノ ピトヨ
     
    本研究の成果は，次の3点にまとめられる。第1の成果は，人間の調性スキーマの学習過程を模すことのできる計算モデルを構築したことである。第2の成果は，音楽聴取の初期経験が調性処理の脳活動に与える影響を脳機能計測実験によって観察したことである。第3の成果は，音楽のグローバル化が進んでいる現代においても，依然として文化間で調性スキーマが大きく異なることを実験的に確認したことである。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 溝部 佳代, 横澤 宏一, 芳賀 早苗
     
    ストレスが生体に与える影響を捉えるには、客観的に測定可能なツールが必要である。快・不快な画像を見た時の反応が、絶食ストレス下で変化するのか、20名の健常者を対象に実験を行った。計測は主観的評価(VAS)、脳磁計、伝統的な自律神経系指標である脈拍、呼吸を用い、平常時と比較した。 脳磁計の結果をみると、絶食時には快刺激に対する応答の低下がみられたことから、絶食時では情動的刺激に対する感受性が変化する可能性が考えられた。脈拍や呼吸では、絶食時と平常時で、違いはみられなかった。以上より、脳磁計は客観的にストレス応答を図る指標として、新たな知見をもたらす可能性があることが見出された。

教育活動情報

主要な担当授業

  • 大学院共通授業科目（教育プログラム）：脳科学研究の展開
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 脳科学、講演、セミナー
  • 大学院共通授業科目（教育プログラム）：社会と健康
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 健康科学，環境，人類生態，遺伝・細胞，代謝，ストレス応答，生体計測，健康情報，栄養、精神的健康
  • 健康科学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 保健科学院
    キーワード : 健康科学，環境，人類生態，遺伝・細胞，代謝，ストレス応答，生体計測，健康情報，栄養、精神的健康
  • 機能情報計測学演習
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 保健科学院
    キーワード : 定量化、脳機能情報、ノイズの除去、活動源の抽出
  • 機能情報計測学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 保健科学院
    キーワード : 定量化、センサ、形態情報、機能情報、可視化、血流代謝、高次脳機能計測
  • 大学院共通授業科目（教育プログラム）：脳科学入門
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 脳, 機能イメージング, fMRI, MEG
  • 実験研究方法特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 保健科学院
    キーワード : 実験計画法，生物化学的研究方法，生理学的研究方法，分子・細胞生物学的研究方法，分析化学的研究方法，医用工学的研究方法，臨床医科学的研究方法，測定データ解析方法
  • 制御工学概論
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 医学部
    キーワード : フィードバック制御、フィードフォワード制御、伝達関数、ラプラス変換
  • 医用電気回路
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 医学部
    キーワード : 交流回路、複素インピーダンス、Ｌ－Ｃ－Ｒ回路、共振、三相交流
  • 医用電磁気学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 医学部
    キーワード : 電荷、電界、電位、電流、磁界、電磁誘導、Maxwellの方程式、静電容量、インダクタンス、誘電体、磁性体
  • 物理数学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 医学部
    キーワード : 複素数、ベクトルの内積と外積、複素記号法、線積分、面積分、テイラー展開、微分方程式、フーリエ級数、フーリエ変換
  • 超音波機器工学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 医学部
    キーワード : 超音波診断装置、音場、振動子、音響レンズ、探触子アレイ、画像再構成、血流
  • 基礎工学実験Ⅰ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 医学部
    キーワード : 電磁気学、交流電圧、電気計測、計測データの取り扱い
  • 基礎工学実験Ⅱ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 医学部
    キーワード : 半導体、電子回路、デジタル回路、光センサー

大学運営

委員歴

  • 2016年04月 - 現在   日本生体医工学会   編集委員長

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