Neurochemical dissociation of memory systems.

The administration of scopolamine, an anticholinergic drug, reduced the ability to recall and recognize stimuli presented previously--abilities thought to require declarative memory. In contrast, measures of procedural memory were unaffected by scopolamine: performance on a serial reaction time task incorporating a repeating stimulus and response sequence showed no difference in acquisition and retention of the sequence after scopolamine or saline. These results suggest that the cholinergic system is required for declarative but not procedural memory.