Decreased alpha bandwidth responsiveness to photic driving in Alzheimer disease.
The power spectra of the photically activated occipital EEGs of 9 mildly to moderately demented probable Alzheimer disease (AD) patients (according to NINCDS-ADRDA criteria), 9 normal age-matched control and 27 normal subjects of different ages were compared. In normal subjects, photic stimulation with rhythmic flashes ranging between 2 and 20 Hz elicited a characteristic response in each EEG bandwidth (delta, theta, alpha, beta1 and beta2). The magnitude of each bandwidth response was a function of the frequency of the photic stimulus. In AD patients the alpha bandwidth response curve was significantly smaller than that of age-matched controls (MANOVA main effect of group, P = 0.018); all the other bandwidth response curves were normal. Therefore, in AD there is a selective abnormality in the alpha bandwidth responsiveness to photic stimulation, probably due to AD pathology in the neuronal generator of the alpha rhythm.
Neuropsychiatric Research Institute, Fargo VAMC, ND 58102.
A L
AL
Politoff
N
N
Monson
P
P
Hass
R
R
Stadter
D000368:Aged; D000513:Alpha Rhythm; D000544:Alzheimer Disease / Q000503:physiopathology*; D000704:Analysis of Variance; D004569:Electroencephalography; D005583:Fourier Analysis; D006801:Humans; D008875:Middle Aged; D009778:Occipital Lobe / Q000503:physiopathology; D010775:Photic Stimulation