@misc{oai:ir.soken.ac.jp:00001102,
 author = {Lam, Khanh and ラム, カン and LAM, Khanh},
 month = {2016-02-17, 2016-02-17},
 note = {The human cortex can be divided into many distinct functional regions, such as the primary somatosensory cortex (S1) and the primary visual cortex (V1). Most of the remaining regions are known as association areas; they respond in a more complicated way to external stimuli. For a better understanding of this complexity we investigated the integrative processing of the human cerebral cortex following multi- and uni-modal stimulation by using magnetoencephalography (MEG).<br />　 In the first study, in order to elucidate the mechanisms underlying the neural process to detect multi-modal stimulation (somatosensory, visual and auditory), we recorded somatosensory evoked magnetic fields (SEFs) following electrical stimulation of the median nerve with continuous visual (cartoon or random dot motion) or auditory (music) interference in 12 normal subjects. Random dot motion included random and coherent motions of the dots. In the hemisphere contralateral to the stimulated nerve, the middle-latency components (35-60ms in latency) were significantly enhanced by visual, but not by auditory stimulation. The dipoles of all components within 60-70ms following stimulation were estimated to be very close to each other, around the hand area of the S1. In the ipsilateral hemisphere, the middle-latency components (70-100ms in latency), the dipoles of which were estimated to be in the secondary somatosensory cortex (S2), were markedly decreased in amplitude by both the visual and auditory stimulation. These changes in waveforms by visual and auditory stimulation are thought to be due to the effects of the activation of polymodal neurons, which receive not only somatosensory but also visual and/or auditory inputs, in areas 5 and/or 7 as well as in the medial superior temporal area (MST) and superior temporal sulcus (STS), although a change of attention might also be a factor causing such findings.<br />　 In the second study, in order to understand the neural process to detect uni-modal stimulation with different features in one specific functional (visual) system we investigated the magnetic response of the human extrastriate cortex in detection of coherent and random motions.<br />　 Although the direction selectivity is a cardinal property of the neurons in the visual motion detection system, recent studies have showed that the motion of numerous elements without global direction (random motion) activates the human and monkey visual system the same as does coherent motion which has a global direction. We used MEG to investigate whether these two motions are processed in distinct neural subsystems with five subjects. Both motions were created by a random dot kinematogram (RDK) with three speeds (0.6, 9.6, and 25°s-1) and used to evoke magnetic responses from the human extrastriate cortex. Response latencies to the simple onset of coherent motion were affected by the speed, whereas those for random motion were not. The estimated origin of the response to coherent motion onset was located lateral (median: 0.7 cm) to that for random motion. Responses to change from coherent to random motion and vise versa differed from those to the simple onset and offset of coherent motion in terms of latencies and estimated origins. Response amplitudes were similar under all stimulus conditions. These findings indicate that the response to random motion is not due to nonspecific activation of the coherent motion detection system but support the view that the human visual system has a subsystem for the process of random motion different from that for coherent motion. We consider that the presence of the subsystem to detect random motion increases the detectability of coherent motion in the visual scene of random motion.<br />　 In conclusion, using MEG we could assess the temporal and the spatial properties of the magnetic responses of the human ccrebral cortex to multi-modal as well as uni-modal stimulation. With high spatial and temporal resolution, MEG seemed to be the best method available to investigate the Complicated neural process in restricted areas., 総研大甲第435号},
 title = {INTEGRATIVE PROCESSING IN THE HUMAN CEREBRAL CORTEX FOLLOWING MULTI- AND UNI-MODAL STIMULATION: MAGNETOENCEPHALOGRAPHIC STUDIES},
 year = {}
}