Impaired prefrontal cortical function and disrupted adaptive cognitive control in methamphetamine abusers: a functional magnetic resonance imaging study.
BACKGROUND
Methamphetamine (MA) abuse is associated with neurotoxicity to frontostriatal brain regions with deleterious effects on cognitive processes. Deficits in behavioral control are thought to be one contributing factor to the sustainment of addictive behaviors in MA abuse.


METHODS
In order to examine patterns of behavioral control relevant to addiction, we employed a fast-event-related functional magnetic resonance imaging design to examine trial-to-trial reaction time (RT) adjustments in 12 MA-dependent subjects and 16 non-substance-abusers. A variant of the Stroop task was employed to contrast the groups on error rates, RT conflict, and the level of trial-to-trial adjustments seen after incongruent trials.


RESULTS
The MA abusers exhibited reduced RT adjustments and reduced activation in the right prefrontal cortex compared to controls on conditions that measured the ability to use exposure to conflict situations (i.e., conflict trials) to regulate behavior. The groups did not differ on accuracy rates or within-trial Stroop conflict effects.


CONCLUSIONS
The observed deficits in trial-to-trial RT adjustments suggest that the ability to adapt a behavioral response based on prior experience may be compromised in MA abusers. These failures to modify behavior based on prior events may reflect a deficit that contributes to drug-seeking behavior.
Salo
Ruth
R
Department of Psychiatry and Behavioral Sciences, University of California, Davis, USA. resalo@ucdavis.edu
Ursu
Stefan
S
Buonocore
Michael H
MH
Leamon
Martin H
MH
Carter
Cameron
C
D000328:Adult; D019969:Amphetamine-Related Disorders / Q000503:physiopathology* / Q000523:psychology*; D001931:Brain Mapping; D016022:Case-Control Studies; D003071:Cognition / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology*