Mapping functional connectivity in patients with brain lesions

Adrian G. Guggisberg, Susanne M. Honma, Anne M. Findlay, Sarang S. Dalal, Heidi E. Kirsch, Mitchel S. Berger, Srikantan S. Nagarajan
2008 Annals of Neurology  
OBJECTIVE-Although electrophysiological measures of functional connectivity between brain areas are widely used, the spatial distribution of functional interactions as well as the disturbance introduced by focal brain lesions remains poorly understood. Based on the rationale that damaged brain tissue can be expected to be disconnected from the physiological interactions among healthy areas, this study aimed to map the functionality of brain areas according to their connectivity with other
more » ... METHODS-Magnetoencephalographic (MEG) recordings of spontaneous cortical activity during resting state were obtained from 15 consecutive patients with focal brain lesions and from 14 healthy controls. Neural activity at each volume element (voxel) in the brain was estimated using an adaptive spatial filtering technique. For each brain voxel, the mean imaginary coherence of all its connections with other brain voxels was then caluculated as an index of functional connectivity, and the results compared across brain regions and between subjects. RESULTS- The magnitude of the mean imaginary coherence of all voxels and subjects was greatest in the alpha frequency range corresponding to the human cortical idling rhythm. In healthy subjects, functionally critical brain areas such as the somatosensory and language cortices had the highest alpha coherence. When compared to healthy controls, all lesion patients had diffuse or scattered brain areas with decreased coherence. Patients with lesion-induced neurological deficits displayed decreased connectivity estimates in the corresponding brain area compared to intact contralateral regions. In tumor patients without preoperative neurological deficits, brain areas showing decreased coherence could be surgically resected without the occurrence of post-surgical deficits. CONCLUSION-Resting state coherence measured with MEG is capable of mapping the functional connectivity of the brain, and can therefore offer valuable information for use in planning resective surgeries in patients with brain lesions, as well as investigations into structuralfunctional relationships in normal subjects.
doi:10.1002/ana.21224 pmid:17894381 pmcid:PMC3646715 fatcat:kzzresi22rclnb5rvdn72bujee