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Ryan Ly, Yuri Saalmann, Sabine Kastner; Distracter filtering across the visual thalamocortical network. Journal of Vision 2013;13(9):237. doi: https://doi.org/10.1167/13.9.237.
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One function of visual attention is to filter out distracting objects. Currently, there is evidence for operations of distracter filtering in areas of the ventral visual stream such as V4 (de Weerd et al., 1999, Nat Neurosci). However, little is known about distracter filtering and its neural mechanisms in other parts of the visual system. We explored distracter filtering in V4, the lateral intraparietal area (LIP) of the dorsal visual stream, and the pulvinar nucleus of the visual thalamus, which has been implicated in distracter filtering from lesion studies (Snow et al., 2009, PNAS; Desimone et al., 1990, CSH Symp Quant Biol). We simultaneously recorded single-neuron activity from these areas of two macaque monkeys performing a variant of the Eriksen flanker task (Eriksen, 1995, Vis Cogn). Macaques were trained to detect a target shape (barrel /bowtie) that was flanked by either congruent distracters (same shape as the target) or incongruent distracters (dissimilar shape to the target). Similar to human behavioral performance, reaction times were faster on congruent versus incongruent trials. We calculated spike density functions for all cells and compared their responses to the target when flanked by congruent versus incongruent distracters. Neurons in V4, LIP, and the pulvinar showed shape selectivity, with more cells showing preference for convex over concave shapes, as previously shown in V4 (Pasupathy and Connor, 1999, J Neurophysiol). When the monkeys correctly identified the target amid distracters, cells were sensitive to the incongruence of nearby distracting stimuli. This sensitivity was seen in both dorsal and ventral visual streams, as well as in the thalamus. These preliminary results suggest that an extensive visual thalamocortical network contributes to distracter filtering, beyond what has been previously shown in the ventral visual stream. The involvement of the pulvinar further supports its important role in visual attention.
Meeting abstract presented at VSS 2013
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