Effects of Acute Aerobic Exercise on Response Inhibition in Adult Patients with ADHD.

Previous studies suggest beneficial effects of aerobic exercise on executive functions, which are a core deficit in ADHD. The aim of the present fMRI study was to investigate acute effects of aerobic exercise on inhibitory control and related brain activation in adult patients with ADHD. 23 patients and 23 matched healthy controls performed on a Go/No-go task in an MRI scanner, following both, an exercise condition involving 30 min of cycling at moderate intensity, and a control condition. ADHD patients compared to healthy controls showed increased brain activation during successful inhibition in the exercise compared to the control condition in parietal, temporal, and occipital regions. Exercise did not improve behavioral performance in either group, but in ADHD patients, exercise-related increases in brain activation and behavioral task performance (i.e., correct inhibition rate) negatively correlated with correct inhibition rate in the control condition. Thus, patients with worse inhibition performance showed stronger exercise-related enhancements, indicating that the lack of improvements on the behavioral level for the whole patient group could be due to ceiling effects. Our findings might be an important step in understanding the neural basis of exercise effects and could, in the long term, help in developing alternative treatment approaches for ADHD.

Countermanding saccades with auditory stop signals: testing the race model.

In a stop signal paradigm to investigate the control of human saccades subjects were instructed to make a saccade to a visual target appearing suddenly l5 degrees to the left or to the right of the fixation point. In 25% of the trials an auditory stop signal was presented after a variable delay that required the subject to inhibit the saccade. The stop signal was presented randomly at the target position, at the opposite side, or at fixation. Using different estimation techniques the average time needed to inhibit a saccade (stop signal processing time, or SSPT) was estimated on the basis of the race model. The SSPT estimates ranging from 50 to 100 ms (depending on subject) are shorter than those from previous studies with visual stop signals. Position of the auditory stop signal did not show an effect on countermanding effectiveness. We found saccadic response times consistent with the race model predictions for two subjects, while a third subject showed small but consistent violations. Moreover, all subjects showed a tendency towards hypometric saccades for responses that could not be inhibited. These findings are discussed with respect to recent neurophysiological results.