The synchronicity of BOLD signal fluctuations throughout the brain has been useful in understanding functionally related brain regions/networks.42–44 Functional connectivity patterns among healthy individuals demonstrate a functional link between various regions known to communicate during various tasks and at rest. In contrast, connectivity patterns among clinical populations deviate considerably from those observed among healthy brains. For example, patients with Alzheimer’s disease have demonstrated disrupted hippocampal and frontal lobe connectivity throughout the brain, as compared to healthy peers.21,22 Furthermore, significant functional connectivity between hemispheres is found among healthy individuals; 22,45–47 whereas, interhemispheric functional connectivity is significantly reduced among clinical populations with compromise in the corpus callosum (CC).48–49 The relationship between CC integrity and functional connectivity was demonstrated by Quigley and colleagues (2003)48, who found patients with agenesis of the CC showed significantly reduced interhemispheric connectivity as compared to healthy controls. Likewise, Johnston et al. (2008)49 demonstrated dramatic reductions in interhemispheric functional connectivity of various functional systems after a complete callosotomy, while intrahemispheric connectivity was relatively preserved. These results implicate the CC as having a significant role in the degree of interhemispheric
