Effects of intranasal methamphetamine on metacognition of agency.

Background: Although methamphetamine abuse has been associated with cognitive deficits, few studies have investigated the acute effects of the drug on complex cognitive performance. This study evaluated the acute effects of intranasal methamphetamine on a computerized task measuring metacognition of agency.
Procedure: Ten nontreatment seeking methamphetamine abusers (2F, 8M) completed this four-session, within-participant, double-blind laboratory study; during each session, participants received one of four doses (0, 12, 25, or 50 mg/70 kg) and completed the metacognition of agency task. In this task, participants were instructed to "catch" falling targets with a mouse and then provide metacognitive judgments about their feelings of control.
Results: Following placebo, judgments of agency were greater under optimal task conditions compared with less than optimal task conditions. Relative to placebo, the 12-mg dose improved task performance, increased judgments of agency under the optimal condition, and decreased judgments of agency under the less than optimal condition. By contrast, the larger doses (25 and 50 mg) increased judgments of agency only under the optimal condition but disrupted performance under the less than optimal condition.
Conclusion: These data show that a low intranasal methamphetamine dose enhanced judgments of agency and performance, while larger doses produced limited effects.