Visual evoked potentials in multiple sclerosis: frequency response shows reduced alpha amplitude.
Visual evoked potentials were measured in a group of 16 multiple sclerosis (MS) patients and in a control group of 20 subjects. With respect to vertex and occipital recordings, latencies of main peaks were prolonged and response amplitudes were reduced in the MS group. As a result of frequency domain analysis we found that the amplitude reduction was not uniform in all frequency ranges: alpha (7-12 (Hz) components of EPs were markedly reduced whereas theta (4-7 Hz) responses were not altered. It is remarkable that the frequency components were altered to a different degree--this may shed some light on the physiological roles of the frequency components: As MS is frequently associated with optic neuritis, our interpretation of this frequency-dependent pattern is based on regarding MS as a model of impaired sensory input to the brain: the fact that in this situation alpha responses are markedly reduced hints at a link between alpha responses and primary sensory processing. Theta responses turned out to be unaltered--i.e., less dependent on sensory inputs--and might thus reflect associative sensory processing. This conclusion for functional roles of EP frequency components has also been drawn from previous investigations of topographic differences of EP frequency components.
Basar-Eroglu
C
C
Institute of Psychology and Cognition Research, University of Bremen, Germany.
Warecka
K
K
Schürmann
M
M
Başar
E
E
D000328:Adult; D000513:Alpha Rhythm; D001303:Auditory Cortex / Q000502:physiology / Q000503:physiopathology; D001921:Brain / Q000502:physiology / Q000503:physiopathology*; D005074:Evoked Potentials, Visual; D006801:Humans; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000503:physiopathology*; D009778:Occipital Lobe / Q000502:physiology / Q000503:physiopathology; D010775:Photic Stimulation; D012016:Reference Values; D013826:Theta Rhythm; D014793:Visual Cortex / Q000502:physiology / Q000503:physiopathology