P3 and other long latency auditory evoked potentials in presenile dementia Alzheimer type and alcoholic Korsakoff syndrome.

The P300 (P3) and other long latency auditory evoked potentials were measured in 15 patients with presenile dementia Alzheimer type (ATD), 16 patients with alcoholic Korsakoff syndrome (KS) and 23 age-matched control subjects. All were drug free for at least four weeks before testing. The latency of the P3 was significantly longer and the amplitude significantly smaller in the ATD group than in both the KS and control groups. The KS group did not differ significantly from the control group in either latency or amplitude of P3 but both the KS and ATD groups had reduced N1 and P2 compared to controls. Using a combination of P3 latency and amplitude, 70% of the ATD patients could be separated from the other groups with no false positives. These findings suggest that evoked potential recording may be of value in the diagnosis of early ATD.