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Dorothy Currey, Matthew Gannon, Nathan Parks; Lateral Masking Reveals Effects of Invading Activity of Short-Term Visual Plasticity. Journal of Vision 2014;14(10):656. doi: https://doi.org/10.1167/14.10.656.
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Short-term visual plasticity refers to alterations of visual representations that occur over periods of seconds to minutes. Short-term plasticity can be readily studied in the human visual system using an artificial scotoma: a stimulus-induced analog of a true retinal scotoma. An artificial scotoma is induced by superimposing a small peripheral gray disc upon a background of dynamic white noise. After several seconds of viewing, the gray disc begins fading from awareness, becoming perceptually filled-in by the surrounding white noise background. Animal neurophysiology has demonstrated that spatial representations within the boundaries of an artificial scotoma become driven by cortical spatial representations beyond the scotoma boundaries (invading activity). Here, we used an artificial scotoma paradigm and lateral masking to provide a psychophysical measure of invading activity in the human visual system. Psychophysical observers were conditioned with an artificial scotoma display for a period of 5.0 seconds (2.0 degree scotoma disc, 5.0 degree eccentricity). Following this conditioning period, a Gabor patch oriented ± 20 degrees was briefly flashed for 48 ms within the boundaries of the artificial scotoma. Two lateral masks (2-degree sinusoidal checkerboards) were also flashed for 48 ms, positioned directly adjacent to the outer boundaries of the artificial scotoma, flanking the Gabor patch location. Lateral masks onset at nine separate SOAs relative to the Gabor (-128, -64, -32, -16, 0, 16, 32, 64, or 128 ms). Lateral masking effects following artificial scotoma conditioning were compared to a stimulus-matched baseline condition. We predicted that the scotoma-induced invading activity should lead to enhanced effects of lateral masking. Comparison of accuracy in the scotoma versus baseline condition revealed exacerbated effects of forward and backward masking at intermediate SOAs. These results provide a psychophysical measure of invading activity in short-term visual plasticity and are consistent with visual feedback playing a role in driving these effects.
Meeting abstract presented at VSS 2014
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