Novel neuroimaging technique and measurement of contrast sensitivity with wide-view stimuli in human visual cortex

Using a novel wide-view visual presentation system for vision research developed by us and visual retinotopic mapping functional magnetic resonance imaging (fMRI). We have investigated the variation of BLOD response, in three visual areas (V1-V3), as a function of visual retintotopic areas and five contrast levels (96%, 48%, 24%, 12% and 6%). Each visual area was identified in each subject using a combination of retinotopic mapping methods and cortical flattening techniques. A checkerboard patterns with five level contrasts were used as the stimuli in this study. We also constructed BLOD responses amplitude tuning curves, averaged across subjects, for three visual areas (V1-V3) and three eccentricities (0-20°, 20-40°, 40- 60°). The result indicated that the peripheral stimulation would lead to lower BLOD responses, compared with the visual areas relative to central field stimulation. The present signal change of each visual area is consistent with the known physiological properties of cells in the corresponding macaque visual areas in previous functional imaging studies. In presented study, we confirmed visual areas V3 showed more sensitivity to contrast, than V2, and than V1 in central and peri-central visual area. More importantly, we revealed the biological responses for peripheral visual areas (40-60°), which the V1-V3 had BLOD signal change only for higher contrast (96%and 48%), but no BLOD response for lower contrast (24%, 12% and 6%).