Auditory brain-stem, middle- and long-latency evoked potentials in mild cognitive impairment.
OBJECTIVE
Mild cognitive impairment (MCI) is a selective episodic memory deficit in the elderly with a high risk of Alzheimer's disease. The amplitudes of a long-latency auditory evoked potential (P50) are larger in MCI compared to age-matched controls. We tested whether increased P50 amplitudes in MCI were accompanied by changes of middle-latency potentials occurring around 50 ms and/or auditory brain-stem potentials.


METHODS
Auditory evoked potentials were recorded from age-matched controls (n = 16) and MCI (n = 17) in a passive listening paradigm at two stimulus presentation rates (2/s, 1/1.5 s). A subset of subjects also received stimuli at a rate of 1/3 s.


RESULTS
Relative to controls, MCI subjects had larger long-latency P50 amplitudes at all stimulus rates. Significant group differences in N100 amplitude were dependent on stimulus rate. Amplitudes of the middle-latency components (Pa, Nb, P1 peaking at approximately 30, 40, and 50 ms, respectively) did not differ between groups, but a slow wave between 30 and 49 ms on which the middle-latency components arose was significantly increased in MCI. ABR Wave V latency and amplitude did not differ significantly between groups.


CONCLUSIONS
The increase of long-latency P50 amplitudes in MCI reflects changes of a middle-latency slow wave, but not of transient middle-latency components. There was no evidence of group difference at the brain-stem level.


CONCLUSIONS
Increased slow wave occurring as early as 50 ms may reflect neurophysiological consequences of neuropathology in MCI.
Irimajiri
R
R
Department of Neurology, Institute for Brain Aging and Dementia, University of California, Irvine, CA 92627, USA.
Golob
E J
EJ
Starr
A
A
D000368:Aged; D000544:Alzheimer Disease / Q000503:physiopathology; D001933:Brain Stem / Q000502:physiology*; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000503:physiopathology*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male