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Kyriaki Mikellidou, Francesca Frijia, Domenico Montanaro, Vincenzo Greco, David Burr, Maria Morrone; Cortical responses to moderate- and high-speed gratings extending 60° in the peripheral visual field. Journal of Vision 2016;16(12):1179. doi: 10.1167/16.12.1179.
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© ARVO (1962-2015); The Authors (2016-present)
We investigated the BOLD response to motion presented to large visual fields. We stimulated the visual cortex using moderate (0.26 c/deg, contrast 50%, 38 deg/sec) and high speed (0.018 c/deg, contrast 50%, 571 deg/sec) drifting gratings, projected to a large field of view (~60°). These stimuli had the same contrast envelope (50%) and temporal frequency (10 Hz), and very similar contrast sensitivity (~500) at all eccentricities. Stimuli differed only in spatial frequency, and hence speed (by a factor of 14). We measured BOLD responses to these stimuli in various subcortical and cortical visual areas with a GE 3T scanner (Excite HDx, GE Medical Systems, Milwaukee, WI), using a block design. Stimuli were presented with a novel optical setup capable of projecting wide-field images at 120 Hz. Retinotopic maps for ten healthy volunteers were constructed using (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. Stimuli were viewed monocularly (right eye). Despite the 14-fold difference in spatial frequency and speed, causing very different stimulation of magno and parvo cells, responses in both the lateral geniculate nuclei and the superior colliculi were similar to the two stimuli. In several cortical areas, including V1 (except the far periphery), V3, V3ab, LOC, hMT+, V6 and V7, the BOLD response was the same to both stimulus speeds. However, there was a distinct preference to moderate-speed gratings in areas of the ventral stream, V2 and V4. And in the extreme periphery of V1, and possibly an adjacent area not previously mapped (that could correspond to the monkey prostriata), there was a clear preference for fast-moving gratings. This points to different selectivity for speed in the dorsal and ventral streams, after primary visual cortex.
Meeting abstract presented at VSS 2016
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