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Selene Schintu, Edward Silson, Zaynah Alam, Eric Wassermann, Sarah Shomstein; Prismatic adaptation modulates inter-hemispheric balance with a subsequent change in visual field coverage. Journal of Vision 2018;18(10):897. doi: 10.1167/18.10.897.
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Prismatic adaptation (PA) is a simple sensorimotor technique that modulates visuospatial cognition. Right-deviating PA (rPA) ameliorates neglect symptoms in patients; whereas, left PA (lPA) produces neglect-like behavior in healthy individuals and is considered a behavioral model of neglect. PA is hypothesized to affect interhemispheric balance by inhibiting the posterior parietal cortex (PPC) contralateral to the prismatic deviation. Specifically, lPA is hypothesized to induce neglect-like behavior by inhibiting the right PPC and releasing the contralateral PPC from interhemispheric inhibition. It has been recently shown that changes in spatial attention can be measured in PPC by quantifying corresponding changes in population receptive fields (pRFs) with fMRI. Since the PPC drives PA-induced visuospatial modulation, this effect should be measurable in PPC by quantifying changes in pRFs. We hypothesized that lPA, as a model of neglect, would lead to a corresponding increase in visual field coverage for the right visual field. This would mimic the rightward hyper-attention characteristic of neglect patients. Healthy volunteers underwent fMRI before and after either lPA (n=20) or rPA (n=20). During each pRF measurement, participants were asked to fixate on a central dot, while scene fragments were displayed on the screen through a bar aperture that gradually traversed the entire visual field. Participants were asked to detect either a: (i) central dot color change (fixation condition), or (ii) presence of a particular scene (attention condition). Consistent with our prediction, lPA increased pRFs visual field coverage in the right and decreased it on the left, whereas rPA produced a different pattern. Our results provide evidence that PA affects visuospatial attention by instant reorganization of response profiles in PPC. These results have implications for understanding the contribution of interhemispheric interactions to attentional selection, as well as the utility of PA as a tool for rehabilitation, and, possibly, visual training in healthy individuals.
Meeting abstract presented at VSS 2018
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