Selective effects of cholinergic treatment on verbal memory in posttraumatic amnesia

The combined effects or orally administered physostigmine and lecithin were assessed in a double-blind study of a single patient with posttraumatic amnesia. Treatment improved verbal recall but not verbal recognition, visual memory, or conceptual reasoning. Both storage and retrieval of words in verbal memory were facilitated. Greater improvement in learning of longer or semantically homogeneous word lists than shorter or semantically mixed lists may indicate that treatment reduced the effects of interstimulus interference. Greater divergence of recognition response biases for semantically homogeneous vs. mixed lists was observed under treatment, reflecting some enhancement of semantic appreciation. Absence of a treatment effect on visual nonverbal memory may be due in part to lateralization of the mesencephalic lesion to the left in this patient. Lack of improvement of encoding capacity, d', or conceptual reasoning may reflect a greater dependence of basal forebrain structures on catecholaminergic than cholinergic mechanisms.