Modularity of Brain Networks for Egocentric and Allocentric Memory-guided Reaching.

Poster Session F - Tuesday, April 16, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Lina Musa^1,3 (lmusa09@yorku.ca), Amirhossein Ghaderi¹, Ying Chen⁶, J. Douglas Crawford^1-5; ¹Centre for Vision Research, York University, Toronto, ON, Canada, ²Vision Science to Applications (VISTA), York University, Toronto, ON, Canada, ³Department of Psychology York University, Toronto, ON, Canada, ⁴Department of Biology York University, Toronto, ON, Canada, ⁵Department of Kinesiology York University, Toronto, ON, Canada, ⁶Centre for Neuroscience Studies, Queen’s University

The brain encodes targets for reaching in egocentric (EGO) and/or allocentric (ALLO) reference frames (Byrne and Crawford 2010). Differences in the cortical activation, but not functional organization, of these two representations have been described (Chen et al., 2014; Neggers et al., 2006). Based on previous findings, we expected increased integration & hubness in the ventral visual stream in ALLO brain networks. Here, we performed a secondary analysis of an event-related fMRI task (Chen et al., 2014). The paradigm consisted of 3 tasks with identical stimulus display but different instructions: remember absolute target location (EGO), remember target location relative to a visual landmark (ALLO), and a nonspatial control, color report. We performed a graph theoretical analysis (GTA) on contrast reduced, time-series data during the memory delay period. GTA measures, including the hubness, clustering coefficient, and efficiency were found, as well as the organization of the network into modules. EGO and ALLO brain networks showed increased functional segregation & integration, relative to control. In both tasks, the network was largely segregated into occipito-dorsal-parietal (ODP) and & temporo-frontal (TF) networks modules. ALLO network demonstrated significantly higher modularity and hubs in the ODP module, than EGO. When the subtracting the common baseline correlation, the EGO showed segregation of occipital brain areas from the OPD module, but ALLO did not. Our results demonstrate that rather than increased ALLO encoding of visual reach targets in the ventral stream, there is increased specialization in the interaction between early visual brain areas and dorsal parietal brain areas.

Topic Area: PERCEPTION & ACTION: Vision