Effects of centrally acting drugs on the frontal midline theta activity in man.

The frontal midline theta activity which appears during a performance of mental tasks has been designated as Fm theta. Sixteen male university students who showed the appearance of Fm theta in 3 consecutive days were given 4 centrally acting drugs, i.e., diazepam 5 mg, amobarbital 80 mg, methylphenidate 15 mg and placebo, in a double-blind, crossover design. Scores were made on the state anxiety scale of Spielberger's State Trait Anxiety Inventory (STAI), and EEGs were recorded monopolarly before and during the performance of an arithmetic addition. The test was done twice, before and one hour after the drug administration. Placebo increased the appearance time of Fm theta, decreased the STAI scores and increased the tasks. Diazepam increased the appearance of Fm theta and decreased the state of anxiety but did not influence the amount of tasks. Amobarbital changed neither the appearance of Fm theta nor STAI scores but decreased the tasks slightly. Methylphenidate failed to influence the appearance of Fm theta but increased both the STAI scores and performed tasks. These results suggest that the appearance of Fm theta is influenced by the drugs and that the relief from anxiety might be involved in the appearance of Fm theta.