Effects of nicotine on smooth pursuit eye movements in healthy non-smokers

Rationale The non-selective nicotinic acetylcholine receptor (nAChR) agonist nicotine has been argued to improve attention via enhanced filtering of irrelevant stimuli. Here, we tested this hypothesis in the context of smooth pursuit eye movements (SPEMs), an oculomotor function previously shown to improve with nicotine in some but not all studies. Objectives In order to test whether nicotine improves performance particularly when the inhibition of distracting stimuli is required, SPEM was elicited in conditions with or without peripheral distractors. Additionally, different target frequencies were employed in order to parametrically vary general processing demands on the SPEM system. Methods Healthy adult non-smokers ( N = 18 females, N = 13 males) completed a horizontal sinusoidal SPEM task at different target frequencies (0.2 Hz, 0.4 Hz, 0.6 Hz) in the presence or absence of peripheral distractors in a double-blind, placebo-controlled, cross-over design using a 2 mg nicotine gum. Results Nicotine increased peak pursuit gain relative to placebo ( p < .001), but an interaction with distractor condition ( p = .001) indicated that this effect was most pronounced in the presence of distractors. Catch-up saccade frequency was reduced by nicotine ( p = .01), particularly at higher target frequencies (two-way interaction, p = .04). However, a three-way interaction ( p = .006) indicated that the reduction with nicotine was strongest at the highest target frequency (0.6 Hz) only without distractors, whereas in the presence of distractors, it was strongest at 0.4-Hz target frequency. There were no effects of nicotine on subjective state measures. Conclusions Together, these findings support a role of both distractor inhibition and general processing load in the effects of nicotine on smooth pursuit.