Temporoparietal electrophysiological differences characterize patients with Alzheimer's disease: a split-half replication study.

One hundred and eighty nine subjects were examined by quantified EEG (qEEG) during the resting awake state. Sixty subjects had probable Alzheimer's disease (AD) and were mild to moderately impaired. There were 129 healthy controls. Differences between patients and controls by topographic mapping demonstrated a pattern of group difference maximal posteriorly, primarily in posterior temporal and/or parietal regions. Frontal regions were much less frequently involved. Long-latency evoked potential derived difference showed similar spatial patterns of difference. By EEG spectral analysis, theta was increased and beta decreased for the AD patients. In addition, the qEEG measures were significantly correlated with neuropsychological test scores related to abilities that are impaired in the early stages of disease, such as delayed recall and verbal fluency. To assess replicability the population was split in half. Regions of interest derived from the first half provided numerical measures for discriminant function analysis. A discriminant function, derived from the first half, correctly identified 86% of all second-half subjects (91% controls, 77% AD).