Physostigmine was given intravenously to a total dose of 3 mg to 13 subjects; a placebo of 0.25 N saline was given intravenously to 10 other subjects; both groups received 1 mg of methscopolamine bromide subcutaneously preceding the intravenous infusions. A “physostigmine syndrome” consisting of decreased speech, slowed thoughts, mild sedation, expressionless faces, nausea, and decreased spontaneous activity was evident following doses of 1.5 to 2.0 mg of physostigmine. The capacity of short-term memory (STM) as measured by digit span tasks was significantly less for the subjects who received physostigmine than for the subjects who received placebo. No difference was observed between the two groups on tasks of consolidation from STM to long-term memory (LTM).
Subiects who received physostigmine did not significantly differ from subjects who received placebo in their mood. However, two subjects in the physostigmine group, and no subjects in the saline group became tearful and depressed.