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Rodika Sokoliuk, Rufin VanRullen; Tracking the spatio-temporal propagation of entrained alpha oscillations across the visual field. Journal of Vision 2013;13(9):312. doi: 10.1167/13.9.312.
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© ARVO (1962-2015); The Authors (2016-present)
Visual perception largely depends on the state of the brain at each moment in time. In particular, recent work demonstrated that the precise phase of ongoing alpha oscillations (~10Hz) at the onset of a target stimulus can predict whether this stimulus will be perceived or not. Here, we employ this alpha phase-dependence of perception in a psychophysical experiment to track the spatio-temporal propagation of entrained alpha oscillations across the visual field: is oscillatory phase invariant over space, or does it propagate like a travelling wave? In each trial, observers (n=9) fixated a central dot on the screen while a disc in the upper-left quadrant oscillated in luminance at the individual alpha frequency of each participant, so as to entrain an alpha oscillation with a specific spatial origin. Flash stimuli at perceptual threshold (adjusted via a staircase procedure) appeared at different positions (logarithmically spaced on the screen to achieve regular spacing on visual cortex) within the upper-left, lower-left or upper-right quadrants, and at different times with respect to the entraining oscillation. Flash detection was reported by pressing a button within a given time delay. We evaluated at each spatial location how the probability of flash detection varied along with the phase of the entraining oscillation. Detection performance presented a global oscillation that was detectable across the entire visual field, peaking around the 'dark' phase of the entraining oscillation. After subtracting this global effect, a significant oscillatory pattern of performance remained visible at several locations; its phase, however, varied significantly across locations, producing a travelling wave that propagated through the visual field. We conclude that it is possible to track, in a psychophysical paradigm, the spatio-temporal dynamics of the propagation of entrained alpha oscillations across the visual field. This propagation takes the form of a travelling wave, impacting perception in its wake.
Meeting abstract presented at VSS 2013
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