Abstract
Area prostriata has been well described in the marmoset monkey, but its homologue in the human cortex remains unclear. Here we use functional magnetic resonance together with a novel wide-field projection system and diffusion tensor imaging (DTI) to delineate the human homologue of area prostriata, investigate its functional properties and explore its connectivity with the visual thalamus. We measured BOLD responses with a GE 3T scanner (Excite HDx, GE Medical Systems, Milwaukee, WI) to construct population receptive field (pRF) maps for nine healthy volunteers using conventional retinotopic mapping stimuli over a large field of view (~60°): (i) horizontal and vertical meridian stimulation; (ii) upper, lower, left and right stimulation of the four visual quadrants; and (iii) checkerboard stimuli to map eccentricity. We stimulated the visual cortex using gratings drifting at moderate speeds (38 deg/sec, 0.26 c/deg) and high speeds (571 deg/sec, 0.018 c/deg), identical contrast (50%), temporal frequency (10 Hz) and contrast sensitivity (~500), projected to a large field of view (~60°). Stimuli were viewed monocularly (right eye). Structural connectivity was explored with probabilistic tractography. pRF mapping revealed an eccentricity representation for the most central part (~20°) of the visual field at the most anterior end of the calcarine sulcus, extending into the parieto-occipital sulcus. The position of this area is consistent with the position of prostriata in the marmoset monkey. In addition, DTI and fiber tractography reveal a white matter tract between the pulvinar and area prostriata, with minimal overlap with the pulvinar-V1 tract, suggesting independent connections. The results demonstrate that, unlike the majority of the visual cortex, area prostriata responds more strongly to very fast than moderate-speed motion, and its structural connectivity is consistent with the hypothesis of a V1-independent thalamic input.
Meeting abstract presented at VSS 2017