SLOW-WAVE ACTIVITY IN THE SPECTRAL-ANALYSIS OF THE ELECTROENCEPHALOGRAM AND VOLUMES OF HIPPOCAMPUS IN SUBGROUPS OF ALZHEIMERS-DISEASE PATIENTS

This study examined patients who fulfilled the National Institute of N eurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association Work Group criteria for probable Al zheimer's disease (AD; n = 35) and controls for magnetic resonance ima ging and psychometric data (n = 16) and for quantitative electroenceph alogram data (n = 34). A cluster analysis performed on neuropsychologi cal variables identified 2 AD subgroups: The ADI group (n = 12) had im paired memory and executive functions but preserved verbal and visuosp atial functions. The AD2 group (n = 23) had global impairment. The AD2 group had higher theta amplitude in the temporo-occipital, centropari etal, and frontal derivation and lower peak and mean frequency than th e AD1 group or controls. Both AD groups had more severe memory deficit s and clearly smaller hippocampal volumes than controls. This may impl icate that the degree of damage in ascending activating systems differ s in these subgroups, although the damage in the hippocampus is equal.