Title: High-Resolution fMRI Studies of Human Visual Cortex
Speaker: Ph.D. Kang Cheng
RIKEN Brain Science Institute

Time: 2014/04/15 Tue 14:00 ~ 16:00
Location: 1st Conference Room, Auditorium and Activity Center, National Yang-Ming University (陽明大學活動中心第一會議室).

Abstract:
In this talk, I will first briefly review our previous efforts exploring human primary visual cortex (V1) with high-resolution (sub-millimeter resolution) functional magnetic resonance imaging (fMRI) [1-5], and then present the results from three unpublished studies, all conducted on a 4 Tesla MRI system. In the first study, using both direct mapping and indirect decoding approaches, we demonstrated that orientation selectivity in human V1 can be relaibly revealed. In particular, we found that large dining veins contribute significantly to orientation-selective BOLD signals. These results are strikingly surprising and invite more detailed anatomical and functional studies of draining veins at various spatial scales. In the second study, we manipulated the spatial resolution of fMRI data and analysed the geometric relationship between 1) the spatial resolution of imaging voxels, 2) the systematic increase and decrease in the proportion of direction-selective voxels, and 3) the repetition periodicity of assumed underlying direction-selective hypercolumns in the human middle temporal complex (hMT+). Using this approach, we were able to indirectly estimate the average size of hypercolumns for motion direction in hMT+, which was approximately 0.7 mm in the narrow dimension. Finally, in the third study elucidating the object-selective responses in human occipito-temrpoal cortex, I will highlight the unique advantage of doing these experiments at higher resolutions.