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Leslie Guadron, Annabelle Blangero, Simon P. Kelly; Pre-Saccadic Modulation of the Visual Evoked Potential. Journal of Vision 2014;14(10):619. doi: https://doi.org/10.1167/14.10.619.
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© ARVO (1962-2015); The Authors (2016-present)
A long line of psychophysics studies has shown that subjects can discriminate stimuli presented at the location of an upcoming saccade better than at any other location. Whereas similar spatially-selective effects on performance due to covert top-down attention have been extensively studied using visual evoked potentials (VEPs), and have provided valuable insights into neural underpinnings, technical challenges hamper VEP measurements for presaccadic targets. Such an approach could illuminate distinctions between presaccadic attention and endogenous covert attention that have been hard to make using psychophysical paradigms. We have developed a paradigm that enables testing for modulation of early visual processing by saccade planning. Subjects make regularly-paced (but uncued) saccades every 800-ms between four targets continuously displayed on a screen in a diamond pattern. By having the subjects focus on their saccade timing, rather than on assessing some aspect of the visual target, we hoped to minimize the contribution of voluntary attention to eye movement planning. The spatial location of the targets were chosen to give rise to a maximal "C1," the earliest, striate-generated VEP component. Task-irrelevant Gabor patterns were presented at either the saccade goal or at the opposite location at various times prior to the next saccade onset. Extensive data have been collected from one subject and no spatially-selective modulation of visual processing (C1 and P1 amplitude) can be observed. In order to obtain a behavioral measure of the locus of attention, in a second experiment we asked subjects to report detection of luminance decrements within the Gabor probes. Despite exhibiting relatively better detection at the saccadic goal, there was still no VEP modulation. Critically, the same subject displays a modulation of her C1 by covert attention in the same contrast discrimination task with endogenous cues and no saccades.
Meeting abstract presented at VSS 2014
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