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MIDIキーボードと機能的磁気共鳴画像法(fMRI)を用い，聴覚フィードバックによって指先の力を調整するときの脳活動を検討した．本研究は，指の力のコントロールにおける聴覚フィードバックの効果と，その時の脳活動について明らかにすることを目的として行った．実験の結果，指先の力を制御する際に音圧と力が対応する聴覚フィードバックが返ってくる場合(Normal条件)の方が，対応していない場合(Reverse条件)よりうまく指先を制御できることが示された．また，力の補正に関わると考えられる脳活動が左角回と右上頭頂小葉で確認された．さらに，左背側前運動皮質や両側の一次聴覚皮質が聴覚フィードバックの音の違いにそれぞれ特異的な応答を示すことが示唆された．この研究は，聴覚と運動の統合メカニズムについて議論する一助となることが期待される．, We conducted an experiment using a keyboard instrument. The purpose of this study was to reveal what kind of auditory feedback is helpful for controlling finger force. Participans were asked to control the force of fingertips depending on auditory feedback, and the brain activities related to the force control were measured with functional magnetic resonance imaging. As a result, it was shown that "Normal condition," in which the intensity of feedback sound increased as the finger force was strengthened, is more effective in controlling the fingertip force than "Reverse condition." Furthermore, we found brain activity associated with adjustment of force control in the left angular gyrus and right superior parietal lobule. In addition, we observed activation patterns specific to feedback sound in the left dorsal premotor cortex and bilateral primary auditory cortex. This study will give an insight into adaptive mechanisms of auditory-motor integration.

Sound symbolism is the idea that a sound makes a certain impression (e.g., phoneme “p” is associated with an impression of smallness) and could be the psychological basis of the word–meaning association. In this study, we investigated the neural basis of sound symbolism. Subjects were required to compare the visual sizes of standard and target stimuli while listening to syllables assumed to create either a larger or smaller impression. Stimulus–response congruence is defined as the agreement between the target size and the syllable’s impression. Behavioral data showed that the subjects displayed a longer reaction time under the incongruent condition than under the congruent condition, indicating that they tended to associate the object size with certain syllables. We used functional magnetic resonance imaging to evaluate the cerebral activity during the task, and found that both semantic- and phonetic-process-related areas of the brain (left middle temporal gyrus and right superior temporal gyrus, respectively) were activated under the incongruent condition. These results suggest that these regions are associated with the incongruence of sound symbolism.

Under an acoustically degraded condition, the degree of speech comprehension fluctuates within individuals. Understanding the relationship between such fluctuations in comprehension and neural responses might reveal perceptual processing for distorted speech. In this study we investigated the cerebral activity associated with the degree of subjective comprehension of noise-vocoded speech sounds (NVSS) using functional magnetic resonance imaging. Our results indicate that higher comprehension of NVSS sentences was associated with greater activation in the right superior temporal cortex, and that activity in the left inferior frontal gyrus (Broca's area) was increased when a listener recognized words in a sentence they did not fully comprehend. In addition, results of laterality analysis demonstrated that recognition of words in an NVSS sentence led to less lateralized responses in the temporal cortex, though a left-lateralization was observed when no words were recognized. The data suggest that variation in comprehension within individuals can be associated with changes in lateralization in the temporal auditory cortex.

音楽聴取は"鳥肌が立つ"ほど強烈な情動経験をたびたび引き起こす。これまで"鳥肌が立つ"という状態を予期することや体験することが、報酬系回路に関連していると報告されてきた。本研究では、音楽による強烈な情動経験の個人差と脳神経系の関連性について、磁気共鳴画像法(magnetic resonance imaging, MRI)を用いた解剖学的検討を行った。19人の被験者は、音楽を聴いて鳥肌が立つような気持ちの時に手元のボタンを押す課題に取り組んだ。実験刺激には、各被験者の鳥肌が立ったことのある曲を使用した。実験の結果、音楽に対して喚起される情動感度の個人差は、右尾状核、左島皮質、右中心後回の灰白質の容積に相関していることが示された。本研究は、鳥肌が立つような審美的体験に関連した解剖学的構造を示し、音楽知覚における大脳辺縁系の報酬系回路の役割を強調するものである。, Music can induce intense emotions and physiological responses, such as "goose bumps", "shivers", or "aesthetic chills". Previous studies have suggested that the reward circuit is related to the anticipation and experience of such chills. In this study, we used structural magnetic resonance imaging to investigate individual differences in the intense emotional responses evoked by music. Nineteen subjects were asked to listen to music and report whether they were feeling chills by pressing a button. Each subject selected the music to which they listened based on its having induced chills previously. Our findings offer evidence that individual differences in sensitivity to music-induced emotion might be associated with the gray matter volume in the right caudate, left insula, and right postcentral gyrus. These findings constitute anatomical evidence related to the timing of the aesthetic chills and underscore the role of mesolimbic reward circuits in music perception.

This paper proposes walk pattern modeling for powered exoskeleton based on complex-valued neural network and reports its validity through experiments. We have been developing a powered exoskeleton to support workers at a nuclear power plant in time of hazard. The objective of the powered exoskeleton is to support a worker wearing a heavy radiation protection suit. We believe that conventional reactive power assist control based on EMG sensors is not feasible because they fail to measure the worker muscle activity robustly in the radiation protection suit as the worker has a lot of sweat in the high temperature and the humidity in the suit. Therefore, we have developed feed-forward control to assist the worker's motion based on the recognition of the worker's motion. Our previous studies use a simple k-nearest neighbor algorithm to model the motion of the powered exoskeleton, however, the algorithm is not for online learning and the estimated trajectory is not as smooth as we expected. This paper proposes a new modeling of walk motion of the powered exoskeleton based on a complex-valued neural network. The complex-valued neural network generally has good properties on learning speed and stability. This paper shows its validity for the modeling of powered exoskeleton's walk through experiments.

Sound symbolism is an idea that sounds itself has the impression. In most of the previous psychology and linguistics researches, stimuli were presented visually with alphabets, and subjects directly answered the impression of the sound. The purpose of this study is that establishing a behavioral paradigm applicable to functional magnetic resonance imaging (fMRI) research when the sound stimulus was presented aurally. In this experiment, we focused on sound symbolism in visual size. Subjects were required to answer visual size difference between standard and target stimulus. Visual stimuli were a gray circle on black background LCD screen. Sound stimuli were /bobo/ and /pipi/, and were assumed to have impression of “bigger” and “smaller,” respectively, according to previous researches. Currently, brain activity of the sound symbolism is examined in MRI using ours previous behavior paradigm. The result suggested that our paradigm is able to use for fMRI study. However, MRI imaging results shows that the location and amount of activity is different by subjects, suggesting the neural substrate of the sound symbolism could vary between individuals. Relationships between the brain differences and individual behavioral differences will be discussed.

Doctor of Philosophy in Engineering, Doshisha University