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Abstract:
Early diagnosis of Alzheimer's disease is essential if
patient populations are to be appropriately targeted for new drug
therapies, but such diagnosis is notoriously difficult using
standard clinical and psychological tests. We have used a high
density, 128-channel EEG system in an attempt to identify changes
in brain activity related to dementia and normal aging. Six 60-sec
epochs of resting, eyes-closed EEG were recorded in healthy young
subjects (aged 17-30 years, N=20), healthy elderly (HE) subjects
(aged 60-90 years, N=20) and elderly subjects with probable
dementia of the Alzheimer's type, pDAT (aged 60-90 years, N=20).
Spectral analysis of the EEG using a fast Fourier transform (FFT)
revealed both generalised and topographically-specific differences
in the power of specific EEG frequency bands between the the pDAT
and HE populations, and between the Young and HE population There
was also a shift in the peak amplitude of the power spectrum
towards lower frequencies from Young to HE to pDAT groups. EEG
coherence, a measure of synchronisation of activity at particular
frequencies between distal brain sites thought to be related to
functional connectivity, also revealed differences between the
groups. The implications of quantitative EEG methods in the study
of normal aging and in clinical diagnosis are discussed.
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