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(10) Localization of the Brain Activity During Stereopsis for Random-Dot Stereo-Grams by use of Spatiotemporal dipole Source Localization Method

Hisashi Toyoshima, Takahiro Yamanoi, Toshimasa Yamazaki, Shin-ichi Ohnishi
Joint 4th International Conference on Soft Computing and Intelligent Systems and 9th International Symposium on advanced Intelligent Systems (SCIS & ISIS2008), pp.140-143, 2008-9

Binocular disparity is one of the most important cues for depth perception of human. Previously, some of the present authors have measured electroencephalogram (EEG) from subjects who were watching random dot stereograms (RDSs) with three types of binocular disparities: no or small or large disparity, and estimated brain areas where the visual information is processed, by use of equivalent current dipole source localization (ECDL) method. The results showed that: 1) the postcentral gyrus (PstCG) is involved in visual processing of stereopsis; and 2) all-channels of averaged EEGs for all subjects had converged and the convergence time for the large RDS disparity is longer than that for the small one. Application of the ECDL method to averaged data for small and large disparities showed that visual processing route before the PstCG consists of two pathways: one is from V1 to V4 and then to the TE field; and the other is from V1 to the MT field and then to the PstCG. This result did not depend on the types of disparity. After the PstCG, ECDs were localized to the superior colliculus (SC) and the frontal visual field (FEF), both of which are involved in ocular movements. At interval between the FEF localization and the EEG convergence, ECDs were localized to the inferior frontal gyrus (IFG) and the middle frontal gyrus (MFG). For RDSs with large disparity, the IFG and MFG ECDs were estimated earlier than those for small disparity, while for large disparity the convergence time and the time when ECDs were localized to the IFG just before the convergence time were later than those for small disparity.

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