Dataset Information

Dissecting the circuit for blindsight to reveal the critical role of pulvinar and superior colliculus.

ABSTRACT: In patients with damage to the primary visual cortex (V1), residual vision can guide goal-directed movements to targets in the blind field without awareness. This phenomenon has been termed blindsight, and its neural mechanisms are controversial. There should be visual pathways to the higher visual cortices bypassing V1, however some literature propose that the signal is mediated by the superior colliculus (SC) and pulvinar, while others claim the dorsal lateral geniculate nucleus (dLGN) transmits the signal. Here, we directly test the role of SC to ventrolateral pulvinar (vlPul) pathway in blindsight monkeys. Pharmacological inactivation of vlPul impairs visually guided saccades (VGS) in the blind field. Selective and reversible blockade of the SC-vlPul pathway by combining two viral vectors also impairs VGS. With these results we claim the SC-vlPul pathway contributes to blindsight. The discrepancy would be due to the extent of retrograde degeneration of dLGN and task used for assessment.

SUBMITTER: Kinoshita M

PROVIDER: S-EPMC6329824 | biostudies-other | 2019 Jan

REPOSITORIES: biostudies-other

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Dissecting the circuit for blindsight to reveal the critical role of pulvinar and superior colliculus.

Kinoshita Masaharu M Kato Rikako R Isa Kaoru K Kobayashi Kenta K Kobayashi Kazuto K Onoe Hirotaka H Isa Tadashi T

Nature communications 20190111 1

In patients with damage to the primary visual cortex (V1), residual vision can guide goal-directed movements to targets in the blind field without awareness. This phenomenon has been termed blindsight, and its neural mechanisms are controversial. There should be visual pathways to the higher visual cortices bypassing V1, however some literature propose that the signal is mediated by the superior colliculus (SC) and pulvinar, while others claim the dorsal lateral geniculate nucleus (dLGN) transmi ...[more]

PMID: 30635570

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Project description:Humans can respond rapidly to viewed expressions of fear, even in the absence of conscious awareness. This is demonstrated using visual masking paradigms in healthy individuals and in patients with cortical blindness due to damage to the primary visual cortex (V1) - so called affective blindsight. Humans have also been shown to implicitly process facial expressions representing important social dimensions. Two major axes, dominance and trustworthiness, are proposed to characterize the social dimensions of face evaluation. The processing of both types of implicit stimuli is believed to occur via similar subcortical pathways involving the amygdala. However, we do not know whether unconscious processing of more subtle expressions of facial traits can occur in blindsight, and if so, how. To test this, we studied 13 patients with unilateral V1 damage and visual field loss. We assessed their ability to detect and discriminate faces that had been manipulated along two orthogonal axes of trustworthiness and dominance to generate five trait levels inside the blind visual field: dominant, submissive, trustworthy, untrustworthy, and neutral. We compared neural activity and functional connectivity in patients classified as blindsight positive or negative for these stimuli. We found that dominant faces were most likely to be detected above chance, with individuals demonstrating unique interactions between performance and face trait. Only patients with blindsight (n = 8) showed significant preference in the superior colliculus and amygdala for face traits in the blind visual field, and a critical functional connection between the amygdala and superior colliculus in the damaged hemisphere. We also found a significant correlation between behavioral performance and fMRI activity in the amygdala and lateral geniculate nucleus across all participants. Our findings confirm that affective blindsight involving the superior colliculus and amygdala extends to the processing of socially salient but emotionally neutral facial expressions when V1 is damaged. This pathway is distinct from that which supports motion blindsight, as both types of blindsight can exist in the absence of the other with corresponding patterns of residual connectivity.

Dataset Information

Dissecting the circuit for blindsight to reveal the critical role of pulvinar and superior colliculus.

Publications

Dissecting the circuit for blindsight to reveal the critical role of pulvinar and superior colliculus.

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