Dorsal Stream Plasticity in Deaf Signers: Neural Adaptations to the Visuospatial Demands of Sign Language

Abstract

The human dorsal visual stream contains a hierarchy of retinotopic maps critical for visuospatial attention and action planning located along the parietal lobe. While experience-dependent plasticity has been characterized in the ventral visual stream, similar characterization remains understudied in dorsal maps. Using fMRI and population receptive field (pRF) mapping in congenitally deaf ASL signers and hearing non-signers (n=11 per group), we demonstrate how the visuospatial demands of ASL reshape the organization of dorsal maps from V3AB into the intraparietal sulcus (IPS0-5). We find that deaf signers have pRFs that demonstrate a shift toward higher eccentricity representation in anterior IPS regions (IPS3-IPS5), which is most pronounced in the left hemisphere. Additionally, deaf signers exhibit larger pRF sizes across the dorsal hierarchy, particularly in the right hemisphere. Finally, pRF centers were shifted to the lower visual hemifield bilaterally in deaf signers, mirroring the spatial location of signing hands during ASL communication. Overall, these findings suggest that the visuospatial demands of sign language during development altered the spatial tuning of dorsal stream regions, aligning with previous findings of experience-dependent plasticity in the ventral stream. The specificity of these effects, both in the lateralization and specific pRF properties affected, suggests a mixture of bottom-up and top-down control during development of the functional architecture of higher-order parietal cortex.