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Stephen Macknik, Hector Rieiro, Jie Cui, Manuel Ledo, M. Reza Afrasiabi, Susana Martinez-Conde; The neural correlates of flicker fusion. Journal of Vision 2013;13(9):318. doi: https://doi.org/10.1167/13.9.318.
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© ARVO (1962-2015); The Authors (2016-present)
Artificial lighting and computer and TV displays rank among the most significant of all of modern society’s innovations, and they all use flickering light, yet the neural mechanisms of flicker perception are unknown. Although each flash of a flickering stimulus in lighting devices are generally emitted for only a fraction of each flicker cycle, they appear as continuous and stable because we perceptually integrate successive flashes in a process called "flicker fusion". We determined the neural mechanisms for flicker fusion using single-unit recording of extracellular activity in area V1 of awake rhesus monkeys. Our stimuli were double-flashed gabor patches optimized to the orientation and position of the each receptive field tested, with varying flicker frequency and interstimulus interval. We found that the onset response to the second flash is practically eliminated in conditions where the interstimulus interval is very short, and it gradually recovers as this interval grows longer, irrespective of the flicker rate, implying that the interstimulus interval is more important parameter to flicker fusion than frequency. Likewise, correlated human psychophysics suggests that the suppression of stimulus transients results in flicker fusion. To further test this hypothesis, we predicted a new illusion, temporal fusion, in which we suppress a target’s termination-response, using a mask, during a double-flash sequence, followed by suppression of the second flash’s onset-response. This leaves solely the initial target’s onset response and the final target’s termination response, and the perception is a single long flash. This confirms that stimulus transients from the mask not only mutually suppress target transients (as we have previously found in visual masking experiments), but that long-term temporal filling-in occurs between stimulus on- and termination transients stimulus (in the absence of intervening transients), and that this is the fundamental neural correlate of flicker fusion.
Meeting abstract presented at VSS 2013
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