Serial visual evoked potential recordings in geriatric psychiatry.

Serial visual evoked potentials to flash and pattern reversal stimuli were recorded in elderly patients with senile dementia of the Alzheimer type (SDAT), multi-infarct dementia (MID) and functional psychiatric illness, and in a group of elderly control subjects. Recordings were made at 6 monthly intervals over a 2 year period. Latency and amplitude of the main components were measured and the flash P2-pattern reversal P100 latency difference value was calculated. In all groups significant changes over time did not occur for any parameters but in the SDAT group the regression coefficient for the latency of the flash P2 component and the flash P2-pattern reversal P100 latency difference was significant, reflecting a trend towards increasing flash P2 latency as time progressed. The flash P2-pattern reversal P100 latency difference was longer in the SDAT and MID groups than in the functional patients, confirming the findings of previous reports. The latency difference in the SDAT group only was significantly greater than that in the control group.