On the role of the corpus callosum in interhemispheric functional connectivity in humans

Abstract

SignificanceThe relation between structural and functional connectivity has profound implications for our understanding of cerebral physiology and cognitive neuroscience. Yet, this relation remains incompletely understood. Cases in which the corpus callosum is sectioned for medical reasons provide a unique opportunity to study this question. We report functional connectivity assessed before and after surgical section of the corpus callosum, including multiyear follow-up in a limited subsample. Our results demonstrate a causal role for the corpus callosum in maintaining functional connectivity between the hemispheres. Additionally, comparison of results obtained in complete vs. partial callosotomy demonstrate that polysynaptic connections also play a role in maintaining interhemispheric functional connectivity.

Early recovery of interhemispheric functional connectivity after corpus callosotomy

“…In the study of Roland et al, 7 the homotopic FCs in primary sensorimotor and visual cortices was less affected than that in the frontal lobes after callosotomy. In our results, we observe that the sensorimotor, parietal lobe and visual regions have lower VMHC than frontal lobes.…”

“…7 Second, this study addresses the question of interhemispheric FC recovery after a prolonged postoperative interval. First, complete resection of the total corpus callosum significantly reduces the interhemispheric FC and increases the intrahemispheric FC, which are consistent as previously reported in one study.…”

“…7 Therefore, they proposed that the compensatory re-establishment of the interhemispheric FC could not occur postnatally after age 2 years. In a cohort of 22 epilepsy patients, Roland et al 7 demonstrated that total callosotomy could almost completely interrupt the interhemispheric FC and VMHC in the immediate postoperative period (day 1).…”

“…The pathophysiological basis of corpus callosotomy is that separation of the corpus callosum could stop the interhemispheric transmission of abnormal neuronal discharges and reduce the frequency of generalized seizures. 6,7 One case report showed recovery interhemispheric FCs in a patient 50 years after callosotomy. 1 The temporal correlation of infraslow (<0.1 Hz) intrinsic brain activity in the absence of overt stimulation or task demands within functionally related brain areas is known as resting state networks.…”

“…3,5 Because the corpus callosum is the major commissure between the two hemispheres, it is unsurprising that complete section of the corpus callosum has been reported to markedly reduce the interhemispheric FC within the first week after total callosotomy in epilepsy patients. 6,7 One case report showed recovery interhemispheric FCs in a patient 50 years after callosotomy. 8 Experimental observations of a callosotomized rhesus monkey also showed that interhemispheric FC recovered by 8 months after callosotomy with intact anterior commissure.…”