Effects of methylphenidate on saccadic responses in patients with ADHD

This study examined the effects of methylphenidate on different measures of saccade control, using a repeated measurement design, and the experimental and statistical control of practice effects. Twenty-seven boys with ADHD (mean age 12.6 years, range 10-15 years) were randomly assigned to two testing order conditions (first on-, second off-medication versus first off-, second on-medication) and accomplished the pro-saccadic overlap and the anti-saccadic 200-ms gap tasks (200 trials each). Methylphenidate was found to reduce pro- and anti-saccadic reaction times, error correction times, and the proportion of direction errors during the anti-saccade task. Furthermore, the drug augmented the proportions of express saccades and error corrections. Overlain practice effects were found for most of these measures. Our results suggest a weakening of the fixation, and a strengthening of the "voluntary" system of saccade control by methylphenidate.