Effect of physostigmine and scopolamine on the memory functions of chess players.

Six young trained chess players received 10 consecutive tasks comprising problematic play position at chess. Each subject was tested four times with drug orders balanced across subjects. Compared with saline placebo, physostigmine (20 microgram/kg i.v.) in the presence of peripheral muscarinic blockade (methylscopolamine 6 microgram/kg i.v.) impaired the performance of good players, but the amount of correct solutions was increased when the initial performance level was low. Scopolamine (6 microgram/kg i.v.) impaired the performance of all subjects, and saline placebo proved inactive. The effect of scopolamine together with physostigmine was about the average of the separate effects of these drugs. The subjects talked less, when mildly sedated, and felt nauseated after the physostigmine treatment. Antimuscarinics with and without physostigmine caused cycloplegia in all subjects.