Schedule of Events | Symposia

Structure-function dependencies in large-scale networks: Novel insights from the split brain

Poster Session E - Monday, March 31, 2025, 2:30 – 4:30 pm EDT, Back Bay Ballroom/Republic Ballroom

Tyler Santander¹ (t.santander@psych.ucsb.edu), Selin Bekir¹, Jessica Simonson¹, Theresa Paul², 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

The structural architecture of the human brain is classically assumed to constrain and enable the emergence of large-scale functional networks. However, decades of network neuroscience research have highlighted that relationships between structural connectivity (SC) and functional network topology are not a trivial, 1:1 linear map—functional connectivity (FC) depends not only upon direct axonal connections, but also upon complex, polysynaptic signaling pathways. Split-brain patients present a unique opportunity to assess the nature of structure-function dependencies: callosotomy is a highly-selective surgical lesion to the largest white matter structure in the human brain, effectively severing communication between the cerebral hemispheres. Here we present data from seven adult callosotomy patients, six of whom were tested post-operatively and one both pre- and post-operatively (from one week to six months post-op). In two patients, surgery was halted short of a full transection, including one with only ~1 cm of splenium spared. Estimates of whole-brain SC were derived via diffusion tensor imaging; FC was assessed during resting-state and naturalistic movie-watching fMRI. For comparison, healthy adult controls were taken from the Human Connectome Project. We implemented polysynaptic communication models alongside methods from network control theory to probe differences in SC-FC relationships between controls and split-brain patients, characterizing marked variability in energy landscapes between partial and full splits. Generative models using simulated callosal lesions in controls further underscored that subcortical structural connections are insufficient to support widespread interhemispheric network function. Together, these findings provide novel insights into the extent to which whole-brain functional networks depend upon the corpus callosum.

Topic Area: OTHER