Cognitive brain potentials and psychological deficits in Alzheimer's dementia and Korsakoff's amnesic syndrome.

Auditory-event-related potentials, including the P300 response, were recorded from 20 patients with Alzheimer-type dementia (ATD), 17 patients with Korsakoff's syndrome (KS) and 23 age-matched control subjects. Each of the subjects was assessed using a version of the Luria Neuropsychological Investigation. Prolonged P300 latency and reduced P300 latency and reduced P300 amplitude, which are features of normal ageing and which also occur, to a greater degree, in ATD, correlated significantly with degree of impairment of language ability in both Alzheimer patients and controls. On the other hand, the association between P300 latency changes and various tests of memory was not consistent across the three subject groups; there was a significant negative correlation between P300 latency and visual memory in ATD and a significant positive correlation in KS, whereas in controls no significant correlation was found. By contrast, P300 latency and memory for words were significantly negatively correlated in controls, but in neither of the patient groups. Detailed studies of language function may further elucidate the complex relationships between neuropsychological measures and P300 changes in normal ageing and dementia.