RECENT PRESENTATIONS

Hart CL, Ilan AB, Gevins A, Gunderson EW, Role K, Colley J, Foltin RW (2006). Neurophysiological effects of smoked marijuana during complex cognitive performance. College on Problems of Drug Dependence, Scottsdale, AZ.

ABSTRACT

Previously, we evaluated the ability of daily marijuana smokers to perform complex cognitive tasks following a single marijuana cigarette and reported that performance was only minimally affected. It is possible that the cognitive tests used in that study were insensitive to many marijuana-related cognitive effects. Therefore, in the current study electroencephalographic (EEG) signals were recorded as daily marijuana users performed additional tests of immediate working memory and delayed episodic memory, before and after smoking marijuana. Healthy research volunteers (N=24), smoking ~20 marijuana cigarettes per week, completed this 3-session outpatient study; sessions were separated by at least 72-hrs. During sessions, participants completed baseline computerized cognitive tasks, smoked a single marijuana cigarette (0%, 1.8%, or 3.9% ?9-THC w/w), and completed additional cognitive tasks. Blood pressure, heart rate, and subjective effects were also assessed throughout sessions. Marijuana produced slower and less accurate responses to previously unseen words on the episodic memory task, due to a shift in response bias. This was accompanied by reduced slow wave evoked potential amplitude, suggesting reduced attentional allocation. Working memory task performance was not affected by marijuana, but EEG theta and beta band power decreased. Heart rate and "positive" subjective-effect ratings were significantly increased in a ?9-THC concentration-dependent manner. These data are consistent with previous studies on the neurophysiological effects of acute marijuana smoking and with the previous finding suggesting that a single dose of marijuana has more muted effects on daily smokers than it does on infrequent users, even when difficult memory tasks are employed. Supported by NIDA grants DA-03746 and DA-12840.