Acute effect of callosotomy on cortical temporal coupling in humans: intraoperative electrocorticographic recording

Objective: To investigate the acute role of the corpus callosum in inter- and intrahemispheric temporal coupling.

Methods: Intraoperative electrocorticography (ECoG) makes it possible to investigate the acute role of the corpus callosum in cortical temporal coupling, or synchrony, without additional surgical intervention, thus avoiding the confounding effects of scalp recordings and the long-term reorganization of functional connectivity. ECoGs were recorded in three patients during callosotomies. Bilateral electrode grids were placed over the frontal cortex. ECoGs were recorded immediately before and after performing the anterior two-thirds callosal transection, were digitalized at a sampling rate of 512Hz, inspected for artifacts, and later analyzed offline. Cross-correlation between inter- and intrahemispheric electrode pairs were obtained for 1Hz bins and special broad bands obtained by principal component analysis for each patient pre- and post-callosotomy.

Results: A statistically significant change was observed in intrahemispheric temporal coupling between electrode pairs that exceeded the confidence limit of correlation.

Conclusions: Present results show that interrupting the influence of the corpus callosum has an acute effect on intrahemispheric activity by decreasing temporal coupling between cortical areas.

Significance: Intrahemispheric temporal coupling does not depend exclusively on ipsilateral cortico-cortical pathways or on subcortical influences, but also on callosal pathways.