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Matthew Gannon, Stephanie Long, Megan Gardner, Nathan Parks; Evidence of disinhibition as a mechanism for short-term plasticity following a simulated peripheral scotoma. Journal of Vision 2017;17(10):499. doi: https://doi.org/10.1167/17.10.499.
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Following loss of visual input, deafferented visual cortex remaps to represent visual space outside of its classical retinotopic boundaries. Long-term and enduring reorganization of this kind is proposed to occur through changes in the functional balance within visual circuits, which begin the process of producing long-lasting changes. Within seconds of deafferentation, measureable changes in the functional balance within visual circuits begin through a mechanism of disinhibition. In this study, we investigated these short-term changes that occur within deafferented human visual cortex during a simulated retinal scotoma (artificial scotoma) paradigm by recording electroencephalogram (EEG) while participants performed a stimulus discrimination task. Participants were conditioned with an artificial scotoma positioned 8.0° in the periphery for 6 seconds prior to a sinusoidal visual probe briefly flashing either within the boundaries of the scotoma or in two extra-scotoma locations. Visual evoked potentials (VEPs) evoked by the onset of these visual probes were used to examine changes in cortical excitability within and outside of the cortical representations of the scotoma region. The orientation of the stimulus probes were also manipulated to be one of five tilts: 0.3°, 0.6°, 1.2°, 3.4°, and 8.0° so that psychophysical orientation functions of stimulus selectivity within the scotoma region could be examined. Our results indicate an increased amplitude in the early-phase P1 component of the VEP, as well as a reduction in the slope of the psychophysical orientation function, for visual probes within the scotoma region. The potentiated early cortical response and broader tuning within the scotoma region are consistent with models of disinhibition as a mechanism of neuroplasticity and topographical reorganization within the human visual system.
Meeting abstract presented at VSS 2017
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