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Brian Barton, Alyssa Brewer; FMRI of the Rod Scotoma: Cortical Projections, Filling-In and Insights into Plasticity. Journal of Vision 2011;11(15):9. doi: 10.1167/11.15.9.
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© ARVO (1962-2015); The Authors (2016-present)
Are ectopic responses in lesion projection zones (LPZs) the result of long-term reorganization (plasticity) or short-term filling-in (adaptation)? We used field-standard travelling-wave and cutting-edge population receptive field (pRF) model functional MRI visual field mapping techniques with 4 types of flickering checkerboard stimuli under photopic and scotopic conditions to measure the effects of the rod scotoma in human early visual cortex. Our main findings are: 1) populations of neurons were silenced within the LPZ of the rod scotoma; 2) conscious perception was correlated with neural activity across stimuli in V1, V2, V3, and hV4; pRFs overlapping the LPZ 3) shifted their pRFs more eccentric from the rod scotoma and 4) changed their pRF sizes. Each of these effects differs in degree and range for each of the maps measured, such that maps with larger pRFs (leading to greater overlap with the rod scotoma) show effects further into their representations of the visual periphery. Thus, ectopic responses in LPZs are not unique identifiers of cortical reorganization, but can be a result of short-term filling-in.
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