Brain Advance Access originally published online on April 3, 2006
Brain 2006 129(5):1096-1112; doi:10.1093/brain/awl064
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Marijuana use is associated with a reorganized visual-attention network and cerebellar hypoactivation
Department of Medicine, University of Hawaii, Honolulu, Hawaii, USA
Correspondence to: L. Chang, Department of Medicine, University of Hawaii, 1356 Lusitana Street, 7th Floor, Honolulu, Hawaii 96813, USA E-mail: lchang{at}hawaii.edu
Attention and memory deficits have been reported in heavy marijuana users, but these effects may be reversible after prolonged abstinence. It remains unclear whether the reversibility of these cognitive deficits indicates that chronic marijuana use does not alter cortical networks, or that such changes occur but the brain adapts to the drug-induced changes. Blood oxygenation-level dependent (BOLD) functional MRI (fMRI) was performed in 24 chronic marijuana users (12 abstinent and 12 active) and 19 age-, sex- and education-matched control subjects during a set of visual-attention tasks with graded levels of difficulty. Neuropsychological tests were also administered on each subject. The two marijuana user groups showed no significant difference in usage pattern (frequency or duration of use, age of first use, cumulative joints used, averaged >2000 joints) or estimated cumulative lifetime exposure of 
-9-tetrahydrocannabinol (THC) (mean 168 ± 45 versus 244 ± 135 g). Despite similar task and cognitive test performance compared with control subjects, active and abstinent marijuana users showed decreased activation in the right prefrontal, medial and dorsal parietal, and medial cerebellar regions, but greater activation in various frontal, parietal and occipital brain regions during the visual-attention tasks (all with P 
0.001, corrected, cluster level). However, the BOLD signals in the right frontal and medial cerebellar regions normalized with duration of abstinence in the abstinent users. Active marijuana users, with positive urine tests for THC, showed greater activation in the frontal and medial cerebellar regions than abstinent marijuana users and greater usage of the reserve network (regions with load effect), suggesting a neuroadaptive state. Both earlier age of first use and greater estimated cumulative dose of THC exposure were related to lower BOLD signals in the right prefrontal region and medial cerebellum. The altered BOLD activation pattern in the attention network and hypoactivation of the cerebellum suggest neuroadaptive processes or alteration of brain development in chronic marijuana users. These changes also may be related to marijuana-induced alteration in resting cerebral blood volume/flow or downregulation of cannabinoid (CB1) receptors. The greater activation in the active compared with abstinent marijuana users demonstrates a neuroadaptive state in the setting of active marijuana use, while the long-term chronic effect of marijuana on the altered brain network may be reversible with prolonged abstinence.
Key Words: cannabis; cerebellum; attention network
Abbreviations:
BOLD = blood oxygenation-level dependent; DMP = dorsal medial parietal; fMRI = functional MRI; IFG = inferior frontal gyrus; MFG = middle frontal gyrus; PCG = post-central gyrus; PET = positron emission tomography; rCBF = regional cerebral blood flow; ROI = regions of interest; SFG = superior frontal gyrus; SPM = statistical parametric mapping; THC = -9-tetrahydrocannabinol
Received September 11, 2005. Revised February 16, 2006. Accepted February 20, 2006.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  D. Tomasi, R.L. Wang, F. Telang, V. Boronikolas, M.C. Jayne, G.-J. Wang, J.S. Fowler, and N.D. Volkow Impairment of Attentional Networks after 1 Night of Sleep Deprivation Cereb Cortex, May 19, 2008; (2008) bhn073v2. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Chang and E. P. Chronicle Functional Imaging Studies in Cannabis Users Neuroscientist, October 1, 2007; 13(5): 422 - 432. [Abstract] [PDF]
|
|