Differences between nicotine-abstinent smokers and non-smokers in terms of visuospatial attention and inhibition before and after single-blind nicotine administration

- The effect of nicotine on visuospatial attention and inhibition was assessed.
- Differences between nicotine-abstinent smokers and non-smokers were explored.
- Baseline differences pertaining to visuospatial attention and inhibition were absent.
- Nicotine seemed to induce speeding of inhibition in non-smokers relative to smokers.
- Results indicate possible nicotine-tolerance in smokers.

The cholinergic system is implicated in visuospatial attention and inhibition, however the exact role is still unclear. Two key mechanisms in visuospatial attention are bias and disengagement. Bias refers to neuronal signals that enhance the sensitivity of the sensory cortex, disengagement is the decoupling of attention. Previous studies suggest that nicotine affects disengagement and (related) inhibition. However the exact relation is still unknown. Furthermore, nicotine-abstinence in 'healthy' smokers may resemble some anomalies of visuospatial attention and inhibition as seen in Attention Deficit/Hyperactivity Disorder (ADHD). Smokers and non-smokers (32 male students) performed in a visuospatial cueing (VSC) task, to assess bias and disengagement, and in a stop-signal task (SST) to assess inhibition. It was expected that nicotine abstinent smokers compared to non-smokers, would show poor disengagement (indicated by an enhanced validity effect) and poor inhibitory control (indicated by an enhanced stop-signal reaction time (SSRT)). It was expected that nicotine would positively affect disengagement and inhibition: hypothesis 1 stated that this effect would be larger in smokers as opposed to non-smokers, in terms of smoking-related deficient inhibitory control. Hypothesis 2 stated the exact opposite, in terms of drug-tolerance. Results indicated no baseline differences. Nicotine enhanced inhibition more in non-smokers relative to smokers. Integrating the results, nicotine-abstinent smokers do not seem to resemble ADHD patients, and do not seem to smoke in order to self-medicate a pre-existing deficit pertaining to mechanisms of visuospatial attention and inhibition. Nicotine may affect inhibition more in non-smokers relative to smokers, consistent with a drug-tolerance account.