Dynamic changes in spatial representation within the posterior parietal cortex in response to visuomotor adaptation

Abstract

Recent studies used fMRI population receptive field (pRF) mapping to demonstrate that retinotopic organization extends from primary visual cortex to ventral and dorsal visual pathways by quantifying visual field maps, receptive field size, and laterality throughout multiple areas. Visuospatial representation in the posterior parietal cortex (PPC) is modulated by attentional deployment, raising the question of whether spatial representation in the PPC is dynamic and flexible and that this flexibility contributes to visuospatial learning. To answer this question, changes in spatial representation within PPC, as measured with pRF mapping, were recorded before and after visuomotor adaptation. Visuospatial input was laterally manipulated, rightward or leftward, via prism adaptation, a well-established visuomotor technique that modulates visuospatial performance. Based on existing models of prism adaptation mechanism of action, we predicted left prism adaptation to produce a right visuospatial bias via an increasing pRF size in the left parietal cortex. However, our hypothesis was agnostic as to whether right PPC will show an opposite effect given the bilateral bias to right visual field. Findings show that adaptation to left-shifting prisms increases pRF size in both PPCs, while leaving space representation in early visual cortex unchanged. This is the first evidence that prism adaptation drives a dynamic reorganization of response profiles in the PPC. Our results show that spatial representation in the PPC not only reflects changes driven by attentional deployment but dynamically changes in response to visuomotor adaptation. Furthermore, our results provide support for using prism adaptation as a tool to rehabilitate visuospatial deficits. SIGNIFICANCE STATEMENTRepresentation of space in the posterior parietal cortex (PPC) is reflective of attentional selection. Deploying attention to a certain spatial location modulates response profiles of a corresponding set of neurons with receptive fields in the corresponding spatial location. Here, we show that visuomotor adaptation accomplished through left-shifting prism adaptation dynamically changes the representation of space in the PPC while preserving early visual representations. This is the first evidence that visuomotor adaptation drives an instant reorganization of spatial representation in PPC. This result has implications for understanding the dynamic organization of spatial representation in the PPC and for the rehabilitation of patients with neglect syndrome, whose spatial attention is compromised.