A double-blind placebo controlled experimental study of nicotine: II - Effects on response inhibition and executive functioning

Rationale: Smokers may show abnormal functioning in prefrontal cortex during acute abstinence, reflecting deficient activity in mesocorticolimbic circuitry. Cognitive correlates of this putatively include impaired response inhibition and other aspects of executive functioning. Objectives: To investigate whether inhibitory control and other executive functions in smokers are impaired during acute abstinence relative to post-nicotine. Methods: 145 smokers were tested twice following overnight abstinence, once after nicotine and once after placebo lozenges (order counterbalanced, double-blind), on: an antisaccade task; a Continuous Performance Task (CPT); a delayed response Spatial Working Memory (SWM) task; and a verbal fluency test. Results: Compared with placebo, nicotine was associated with better inhibitory control on the antisaccade task and fewer impulsive responses to filler stimuli (motor errors) on the CPT; at the first assessment only, nicotine also reduced impulsive responses to ‘catch’ stimuli on the CPT. However, it did not affect CPT response bias (an index of impulsive vs. cautious decision-making), spatial working memory, or verbal fluency. Conclusions: Smoking abstinence appears to be associated with difficulty in inhibiting prepotent motor responses, and nicotine to attenuate this difficulty. However, more ‘cognitive’ forms of inhibitory control (e.g. decision-making) and the other aspects of executive function tested here appear to be unaffected