| Co-Investigator(Kenkyū-buntansha) |
NAGANO Takashi Hose University School of Engineering, Professor, 工学部, 教授 (30198345)
SAITOH Hideaki Tamagawa University School of Engineering, Professor, 工学部, 教授 (30215553)
WAMURA Yoshiaki Toho University School of Medicine, Professor, 医学部, 教授 (20057508)
INUI Toshiro Kyoto University, Faculty of Letters, Professor, 大学院・情報学研究科, 教授 (30107015)
TANAKA Keiji The Institute of Physical and Chemical Research, Information Science Laboratory, Director, 脳科学総合研究センター, ディレクター (00221391)
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| Research Abstract |
In this research project we conducted systematic studies on higher-order cognitive processes in the brain concerning perception of sensory information.
Research activities have been centered on (1) the mechanisms for central representation of perceptual information, (2) functional imaging of cognitive processes, and (3) theoretical conceptualization and modeling of information processing for cognition. We have obtained a number of novel findings with physiological studies on subhuman primates, with brain-imaging studies on human subjects, and with theoretical and modeling studies. A major breakthrough for the understanding of the secondary somatosensory area in the cerebral cortex of primates has been provided by findings on detailed neuronal representation of body parts. This was achieved by analyzing information-processing properties of individual cells conveying spatially characterized information about body parts. In the visual association cortex, two major streams of information pr
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ocessing have been proposed. In the ventral stream, detailed functional organization of columnar structures for object recognition have been discovered. This was achieved by analyzing both functional properties of cells and histochemical studies in the infereotemporal part of the cerebral cortex of monkeys. Color-information coding has also been quantified with a new approach of hue representation mapping. On the other hand, in the dorsal stream, optic flow information in the MST area in the parietal cortex has been quantitatively studied at a neuronal level. Response properties of individual cells to moving objects with various speeds were found to be appropriate for providing cognitive motion sense measured by psychophysiological studies. Measurement of magnetoencephalographic (MEG) activity revealed that information processing for visual search progresses from the occipital peri-striatal areas to fusiform area, and then to the intraprietal areas. This was due to the application of visual-search tasks looking into mechanisms for object detection under pop-out and non-pop-out conditions. It was also found that the parietofrontal informational flow developed while subjects underwent mirror-image discrimination tasks. Furthermore, functional MRI measurement revealed a process by which the activity foci in the fusiform gyrus, posterior temporal cortex and the premotor cortex are involved in recognizing object from view points that are novel to subjects. One of the remarkable discovery made by cellular recording in the inferotemporal cortex was that object-recognizing cells were also sensitive to binocular disparity of objects. This finding means that information about spatial localization of objects, that has been viewed as processed in the dorsal stream in the visual pathway, is also processed in the ventral stream to provide the combination of two different sets of information. Theoretical studies revealed a new mechanism of information processing : modulation of visual information coming through the bottom-up projection pathways by top-down processes. It was also proposed that a theoretical model for processing temporal and spatial frequency analysis of local visual information can account for primary and secondary motion perception. Less
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