Effects of frequent marijuana use on memory-related regional cerebral blood flow.
It is uncertain whether frequent marijuana use adversely affects human brain function. Using positron emission tomography (PET), memory-related regional cerebral blood flow was compared in frequent marijuana users and nonusing control subjects after 26+ h of monitored abstention. Memory-related blood flow in marijuana users, relative to control subjects, showed decreases in prefrontal cortex, increases in memory-relevant regions of cerebellum, and altered lateralization in hippocampus. Marijuana users differed most in brain activity related to episodic memory encoding. In learning a word list to criterion over multiple trials, marijuana users, relative to control subjects, required means of 2.7 more presentations during initial learning and 3.1 more presentations during subsequent relearning. In single-trial recall, marijuana users appeared to rely more on short-term memory, recalling 23% more than control subjects from the end of a list, but 19% less from the middle. These findings indicate altered memory-related brain function in marijuana users.
Block
Robert I
RI
Department of Anesthesia, University of Iowa, Room 5140, Westlawn Building, Iowa City, IA 52242, USA. robert-block@uiowa.edu
O'Leary
Daniel S
DS
Hichwa
Richard D
RD
Augustinack
Jean C
JC
Boles Ponto
Laura L
LL
Ghoneim
M M
MM
Arndt
Stephan
S
Hurtig
Richard R
RR
Watkins
G Leonard
GL
Hall
James A
JA
Nathan
Peter E
PE
Andreasen
Nancy C
NC
D000704:Analysis of Variance; D002531:Cerebellum / Q000098:blood supply / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects* / Q000502:physiology; D006624:Hippocampus / Q000098:blood supply / Q000187:drug effects; D006801:Humans; D008385:Marijuana Smoking / Q000009:adverse effects*; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D008569:Memory Disorders / Q000139:chemically induced*; D017397:Prefrontal Cortex / Q000098:blood supply / Q000187:drug effects; D013997:Time Factors; D014055:Tomography, Emission-Computed / Q000379:methods