Neural effects of methylphenidate and nicotine during smooth pursuit eye movements

- We investigated neural and behavioural effects of nicotine and methylphenidate in 82 healthy males
- A smooth pursuit eye movement paradigm was used in fMRI to investigate performance and BOLD effects
- There was no influence of either compound on behavioural measures of smooth pursuit
- The methylphenidate group exhibited increased left frontal eye field activation in contrast to the nicotine group

IntroductionNicotine and methylphenidate are putative cognitive enhancers in healthy and patient populations. Although they stimulate different neurotransmitter systems, they have been shown to enhance performance on overlapping measures of attention. So far, there has been no direct comparison of the effects of these two stimulants on behavioural performance or brain function in healthy humans. Here, we directly compare the two compounds using a well-established oculomotor biomarker in order to explore common and distinct behavioural and neural effects.MethodsEighty-two healthy male non-smokers performed a smooth pursuit eye movement task while lying in an fMRI scanner. In a between-subjects, double-blind design, subjects either received placebo (placebo patch and capsule), nicotine (7 mg nicotine patch and placebo capsule), or methylphenidate (placebo patch and 40 mg methylphenidate capsule).ResultsThere were no significant drug effects on behavioural measures. At the neural level, methylphenidate elicited higher activation in left frontal eye field compared to nicotine, with an intermediate response under placebo.DiscussionThe reduced activation of task-related regions under nicotine could be associated with more efficient neural processing, while increased hemodynamic response under methylphenidate is interpretable as enhanced processing of task-relevant networks. Together, these findings suggest dissociable neural effects of these putative cognitive enhancers.