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Exogenously-driven interhemispheric functional synchrony in the split-brain

Poster Session F - Tuesday, March 10, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Tyler Santander¹ (), Selin Bekir¹, Theresa Paul², Jessica Simonson¹, Valerie Wiemer², Henri Skinner¹, Lena Hopf³, Anna Rada³, Friedrich Woermann³, Thilo Kalbhenn³, Barry Giesbrecht¹, Christian Bien³, Olaf Sporns⁴, Michael Gazzaniga¹, Lukas Volz², Michael Miller¹; ¹University of California, Santa Barbara, ²University of Cologne, ³Bielefeld University, ⁴Indiana University

Large-scale functional networks in the human brain follow a well-characterized interhemispheric organization, with the topography of individual systems appearing as near mirror images across the left and right cerebral hemispheres. The corpus callosum (CC) is thought to provide the essential scaffolding upon which information may be efficiently exchanged and integrated between specialized processing nodes in each hemisphere. We recently reported on a new cohort of adult corpus callosotomy patients who underwent resting-state fMRI, demonstrating that full transection of the CC broadly obliterated typical patterns of interhemispheric functional connectivity (FC); however, some sensorimotor networks appeared to remain integrated, despite evidence for behavioral disconnection effects. The present study therefore sought to determine how synchronized exogenous inputs may produce apparent interhemispheric FC in the absence of direct lines of communication between the left/right hemispheres. Eight adult split-brain patients (2 partial, 6 complete) completed resting-state fMRI in addition to 15 minutes of passive movie-watching (using a stimulus set from the Human Connectome Project). We employed multiple network neuroscience methods, including whole-brain analyses of FC, data-driven community detection, and an edge time series approach for analyzing functional network dynamics, to assess differences between intrinsic (resting) and extrinsic (movie-watching) network states. Results highlight distributed increases in interhemispheric FC beyond mere sensorimotor systems. These findings may inform cross-cueing and other behavioral strategies split-brain patients use to coordinate behavior ‘outside the brain’, given myriad synchronized perceptual inputs to each disconnected hemisphere.

Topic Area: PERCEPTION & ACTION: Other