P50 gating deficit in Alzheimer dementia correlates to frontal neuropsychological function.
BACKGROUND
Cognitive inhibition processes were found to be deficient early in the clinical course of Alzheimer's disease (AD). The inhibition of redundant information is a precondition for efficient cognitive processing and presumably modulated by prefrontal attentional networks. Deficits in the suppression of the evoked potential P50 response to paired clicks are well known in schizophrenic patients and undergo cholinergic modulation. In this study, we aimed to investigate inhibitory gating deficits of P50 in AD and their relation to neuropsychological measures.


METHODS
P50 suppression was assessed in 19 AD-patients in comparison to a young and elderly control group (n=17 each) and related to MMSE and specific neuropsychological assessments.


RESULTS
Patients showed reduced sensory gating compared to healthy elderly (p<0.021) and exhibited significantly higher N40-P50-amplitudes. There were no age or gender effects in controls. Frontal neuropsychological tests (TMT-B, verbal fluency) and working memory requiring inhibition, but not declarative memory functions, were significantly correlated with inhibitory gating and test amplitude in both, AD-patients and controls.


CONCLUSIONS
The results support an early inhibitory deficit interfering with executive functions and working memory in AD independent from physiological aging. P50 gating might be applicable as a marker for inhibition deficits and thereby be important for prognosis estimation.
Centre for Psychosocial Medicine, Department of General Psychiatry, University of Heidelberg, Vossstr. 2, 69115 Heidelberg, Germany. Christine.Thomas@med.uni-heidelberg.de
Christine
C
Thomas
Ingo
I
vom Berg
Andre
A
Rupp
Ulrich
U
Seidl
Johannes
J
Schröder
Daniela
D
Roesch-Ely
Stefan H
SH
Kreisel
Christoph
C
Mundt
Matthias
M
Weisbrod
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D000544:Alzheimer Disease / Q000503:physiopathology*; D001288:Attention / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D001921:Brain / Q000503:physiopathology*; D003071:Cognition / Q000502:physiology*; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D013997:Time Factors