Chronic cannabis users show altered neurophysiological functioning on Stroop task conflict resolution.
BACKGROUND
Chronic cannabis use has been related to deficits in cognition (particularly memory) and the normal functioning of brain structures sensitive to cannabinoids. There is increasing evidence that conflict monitoring and resolution processes (i.e. the ability to detect and respond to change) may be affected.


OBJECTIVE
This study examined the ability to inhibit an automatic reading response in order to activate a more difficult naming response (i.e. conflict resolution) in a variant of the discrete trial Stroop colour-naming task.


METHODS
Event-related brain potentials to neutral, congruent and incongruent trials were compared between 21 cannabis users (mean 16.4 years of near daily use) in the unintoxicated state and 19 non-using controls.


RESULTS
Cannabis users showed increased errors on colour-incongruent trials (e.g. "RED" printed in blue ink) but no performance differences from controls on colour congruent (e.g. "RED" printed in red ink) or neutral trials (e.g. "*****" printed in green ink). Poorer incongruent trial performance was predicted by an earlier age of onset of regular cannabis use. Users showed altered expression of a late sustained potential related to conflict resolution, evident by opposite patterns of activity between trial types at midline and central sites, and altered relationships between neurophysiological and behavioural outcome measures not evident in the control group.


CONCLUSIONS
These findings indicate that chronic use of cannabis may impair the brain's ability to respond optimally in the presence of events that require conflict resolution and hold implications for the ability to refrain from substance misuse and/or maintain substance abstention behaviours.
Battisti
Robert A
RA
School of Psychology, University of Wollongong, Wollongong, Australia. robert.battisti@sydney.edu.au
Roodenrys
Steven
S
Johnstone
Stuart J
SJ
Pesa
Nicole
N
Hermens
Daniel F
DF
Solowij
Nadia
N
D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology; D016022:Case-Control Studies; D002908:Chronic Disease; D003071:Cognition / Q000187:drug effects*; D003220:Conflict, Psychological; D004569:Electroencephalography; D004585:Electrooculography; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D002189:Marijuana Abuse / Q000503:physiopathology / Q000523:psychology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D011930:Reaction Time; D013997:Time Factors; D055815:Young Adult