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Amelia Hunt, Kay Ritchie, Lawrence Weiskrantz, Arash Sahraie; Remapping of an unseen stimulus. Journal of Vision 2010;10(7):205. doi: https://doi.org/10.1167/10.7.205.
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© ARVO (1962-2015); The Authors (2016-present)
When the eyes move, the visual world shifts across the retina. In visual cortex, this means information represented by one population of neurons will suddenly be represented by another population, sometimes transferring from one hemisphere to another. Saccadic remapping is the predictive response of neurons that has been shown to precede the retinotopic shift of stimuli caused by an eye movement. We examined whether conscious perception of a visual stimulus and an intact V1 are prerequisite to remapping stimuli into expected coordinates. Stimuli below the threshold for detection were presented in the blind field of patient DB, who has left homonymous hemianopia after surgical removal of the right striate cortex. Using a two-alternative forced-response procedure, DB performed at chance level (∼50%) when asked to detect a target presented within his blind field while fixating on a fixation cross. However, when he executed a saccade that would bring the visual target into his intact field, his accuracy improved to 89%, even though the stimulus was removed at saccade onset, and never entered his sighted field. Despite the increase in sensitivity, DB reported no conscious awareness of the stimulus. Saccades of equal size and eccentricity that would not bring the stimulus into his sighted field did not elevate detection. The results suggest that the intact visual hemifield may have predictively responded to a stimulus in the blind field, even though that stimulus was neither detected nor consciously perceived. This predictive response improved detection, but did not lead to explicit awareness.
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