Drugs and human memory: effects of low doses of nitrazepam and hyoscine on retention.

1 The effects of diazepam (5 mg) and hyoscine hydrobromide (0.3 mg) were assessed in two memory tasks: short-term retention of digit strings and the free recall of items from categorizable lists. 2 One hundred and two healthy subjects were tested in an independent-groups design. Subjects were assigned randomly to either placebo, diazepam or hyoscine groups. Treatments were administered orally under double-blind conditions. 3 The short-term retention of digits was impaired to an equivalent degree and locus for both drugs (P less than 0.05). This effect was ascribed to the action on primary memory. 4 The drugs produced no significant effects on the recall of categorizable lists either in terms of the number of words recalled or the cohesiveness of categorical recall. 5 These results demonstrate that drugs of different pharmacological actions produce isomorphic psychological deficits in memory and that 'anti-memory' effects on one task should not be extrapolated to all aspects of memory.