Relationships between EEG coherence and neuropsychological tests in dementia

Previous research has demonstrated differences in resting state EEG coherence among groups of subjects with dementia of the Alzheimer type (DAT), multi-infarct dementia (MID), and normal elderly controls. Since reduced coherence between brain sites has been thought to reflect functional disconnection between brain areas, we hypothesized that decreased coherence would be associated with cognitive dysfunction as assessed by neuropsychological tests. We correlated several neuropsychological tests with four coherence variables and found that reduced coherence was associated with impairment on specific neuropsychological tests in ways that conform to and supplement current knowledge about the localization of brain functions. The results are consistent with the hypothesis that coherence reflects a functional breakdown in communication between brain areas, and that coherence may be a more precise way to localize brain function than other EEG variables.