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Shude Zhu, Li Zhang, Rudiger von der Heydt; Can the visual cortex represent the invisible?. Journal of Vision 2017;17(10):348. doi: 10.1167/17.10.348.
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In everyday vision objects often occlude others from sight, but objects are perceived as permanent despite temporary occlusions. Observations on border ownership coding in low-level visual areas (V1, V2) suggested an influence from object representations at a higher level that have some persistence (O'Herron & von der Heydt, JOV 11(2):12, 2011). We recorded from neurons of areas V2 and V4 searching for persistence of object-evoked activity during temporary occlusion. Monkeys performed a visual foraging task in which they sequentially fixated individual figures of an array of 10 figures in search for reward. The array was constructed so that fixating one figure would, in most cases, bring another figure into the receptive field (RF) of the neuron under study, while in other cases it would bring uniform background into the RF. During the presentation of the array, a grating of opaque stripes drifted over the array, variably occluding some of the figures. To a human observer, the 10 figures appeared permanent despite the temporary occlusions. The fixations produced 4 different conditions, depending on whether the RF was on an occluding stripe or not, and whether there was a figure at the location of the RF or not. We determined the average firing rate for each condition and calculated a permanence index PERMI= (OccludedFigure – OccludedNothing) / (VisibleFigure – VisibleNothing). Preliminary results suggest that V4 contains a small proportion of neurons (8/86) with high permanence (PERMI >0.5), whereas no such neurons were found in V2 (0/43). The distribution of recording locations suggests spatial clustering of high permanence neurons within V4. Thus, V4 might be involved in providing object permanence.
Meeting abstract presented at VSS 2017
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