METHAMPHETAMINE EFFECTS ON COGNITIVE PROCESSING DURING EXTENDED WAKEFULNESS

We examined the effects of both 5- and 10-mg/70 kg body weight of d-me thamphetamine HCl on high event rate vigilance and tracking performanc e in a 13.5-hr sustained-performance session during one night of sleep loss. At 0116 hours, participants were administered either a 5 mg/70 kg oral dose of d-methamphetamine (n = 10), 10 mg/70 kg d-methamphetam ine (n = 10), or a placebo (n = 10) using standard double-blind proced ures. Performance on all measures degraded markedly during the night i n the placebo group. Both the 5- and 10-mg methamphetamines treatment reversed an initial decline in d', and reversed increases in nonrespon ses (lapses) and tracking error within approximately 3 hr of administr ation. No evidence that amphetamine treatment increased impulsive resp onding (fast guesses) was observed. The magnitude of the performance e ffects of the methamphetamine treatments was similar at 3 hr postadmin istration. However, the effects of the 5-mg dose were shorter-lived, d isappearing by the last testing session (6.5 hr postadministration), w hereas effects of the 10-mg dose tended to remain throughout testing. Both amphetamine treatments decreased subjective sleepiness during the night and tended to increase subjective sleep latencies during a post -testing sleep period.