No Disconnection Syndrome after Near-Complete Callosotomy

Abstract Sensorimotor processing in the human brain is largely lateralized, with the corpus callosum integrating these processes into a unified experience. Following complete callosotomy, this integration breaks down, resulting in disconnection syndromes. We asked how much of the corpus callosum is sufficient to support functional unity—the absence of disconnection syndrome—by comparing three complete callosotomy patients with one retaining only the splenium. Using lateralized tasks across visual, tactile, visuospatial, and language domains, we predicted domain-specific deficits in the splenium-only patient based on established anatomical models of callosal topography. Strikingly, while complete callosotomy patients exhibited disconnection syndromes, the splenium patient demonstrated functional unity across all domains—as if his entire corpus callosum were intact. Our findings highlight the brain’s remarkable capacity to maintain behavioral integration through minimal preserved pathways, highlighting how the structure-dependent reorganizational capacity of the human brain allows to preserve functional unity. Competing Interest Statement The authors have declared no competing interest. Footnotes This revised version improves the clarity of the manuscript through some text edits, figure updates, and formatting adjustments. Specifically, we refined the wording in several sections to enhance readability and clarity, and updated select figures to better communicate the main findings of our study. No new data were added, and the overall conclusions remain unchanged.