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Matthew Gannon, Stephanie Long, Nathan Parks; The Spatial Extent of Short-Term Plasticity Effects in the Human Visual System. Journal of Vision 2015;15(12):998. doi: 10.1167/15.12.998.
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© ARVO (1962-2015); The Authors (2016-present)
Depriving a small retinal area of patterned inputs against a dynamic background, known as an artificial scotoma, allows for investigations of the immediate changes in cortical visual representations in response to a loss of afferent sensory input (short-term plasticity). Previous research with artificial scotomas (Parks & Corballis, 2012) has demonstrated effects in the sensory components of the visual evoked potential (VEP) consistent with the occurrence of disinhibition within visual cortical scotoma representations and invading activity from surrounding spatial representations. This experiment sought to further probe the spatial extent of these effects by constructing a periscotoma spatial map of disinhibition and invading activity using event-related potentials (ERPs) in an artificial scotoma paradigm. EEG was recorded over two experimental sessions while participants viewed an artificial scotoma display and performed a two-alternative forced choice task, discriminating the tilt of a gabor probe. Scotoma discs were conditioned, bilaterally, for a six second period after which time varying spatial locations were probed relative to the edge of an artificial scotoma. These locations were two positions inside of the scotoma region, 1º and 3º from the edge of the scotoma disc, and three locations outside of the scotoma region, 1º, 3º, and 6º from the edge of the disc. A sham condition used an identical scotoma-probe configuration, with the exception that the scotoma discs were presented only one second prior to probe onset so as to minimize plasticity effects. VEPs were compared between scotoma and sham conditions at each of the five locations to examine modulations in early visual components (P1 and N1) attributable to the induction of short-term plasticity. Preliminary results reveal differential modulations these components between positions within, bordering, and distal from the artificial scotoma. These results support the induction of disinhibition within scotoma boundaries and establish the spatial limits of invading activity.
Meeting abstract presented at VSS 2015
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