Cholinergic enhancement and REM sleep latency in the aged: lecithin does not reproduce physostigmine effect.

The administration of lecithin has failed to improve memory in aged or demented individuals. We studied the effect of lecithin on another cholinergic function, REM sleep latency. Intravenous doses of physostigmine shortened the latency to the first REM sleep period, but oral lecithin did not. In contrast to physostigmine, brain cholinergic function may not be enhanced by lecithin, which may explain why lecithin does not improve cognitive function.