Chronic smoking, but not acute nicotine administration, modulates neural correlates of working memory.
BACKGROUND
Beyond the amelioration of deprivation-induced impairments, and in contrast to effects on attentional processes, the cognitive-enhancing properties of nicotine on working memory (WM) operations remain unclear.


OBJECTIVE
In an effort to elucidate potential enhancing effects, we explored the impact of transdermal nicotine on neural functioning in minimally deprived smokers and, in addition, assessed differences between smokers and non-smokers using a mixed block/event-related fMRI design that attempted to isolate specific central executive operations (attentional switch events) within general WM function (task blocks).


METHODS
In task blocks, participants performed a continuous counting paradigm that required the simultaneous maintenance of, and frequent switching of attentional focus between, two running tallies in WM on some trials. Cigarette smokers (n = 30) were scanned twice, once each with a nicotine and placebo patch, while non-smokers (n = 27) were scanned twice with no patch.


RESULTS
Across both groups, task blocks were associated with bilateral activation, notably in medial and lateral prefrontal cortex (PFC), anterior insula, and parietal regions, whereas individual attentional switch trials were associated with activation in a similar, but predominantly left-lateralized network. Within the smoker group, although nicotine increased heart rate, altered performance and mood, and reduced tobacco cravings, no acute drug (state-like) effect on brain activity was detected for either the task or switch effects. However, relative to non-smokers, smokers showed greater tonic activation in medial superior frontal cortex, right anterior insula, and bilateral anterior PFC throughout task blocks (trait-like effect).


CONCLUSIONS
These data suggest smokers require recruitment of additional WM and supervisory control operations during task performance.
Sutherland
Matthew T
MT
Neuroimaging Research Branch, National Institute on Drug Abuse-Intramural Research Program, NIH/DHHS, 251 Bayview Blvd., Baltimore, MD 21224, USA. sutherlm@nida.nih.gov
Ross
Thomas J
TJ
Shakleya
Diaá M
DM
Huestis
Marilyn A
MA
Stein
Elliot A
EA
D000279:Administration, Cutaneous; D000328:Adult; D001921:Brain / Q000187:drug effects / Q000503:physiopathology*; D056344:Executive Function / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects / Q000502:physiology*; D008875:Middle Aged; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D010919:Placebos; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology; D012907:Smoking / Q000503:physiopathology*; D014029:Tobacco Use Disorder / Q000503:physiopathology
D010919:Placebos; D009538:Nicotine