Analysis of finger tapping parameters in people with ADHD

Spontaneous finger tapping, a measure of spontaneous motor tempo is thought to reflect the pace of an internal attentional timing mechanism, capable of adapting to external temporal events. Although people with ADHD display difficulties in timing of paced motor tasks and evidence altered time perception, studies have failed to show a difference in spontaneous finger tapping rate and have demonstrated inconsistent findings regarding finger tapping variability. We hypothesized that a more detailed analysis of finger tapping, which included the two main finger tapping phases: the touch-phase, defined as the time between onset and offset of the finger tap, and the off-phase, the period between offset and onset, would reveal a significant difference between people with and without ADHD. For this purpose, a highly sensitive system for finger tapping recording and analysis was developed. Finger tapping analysis was carried out on a total of 109 subjects; 68 had been diagnosed with ADHD, and 41 were without any diagnosis (control). We found that the variability of the touch phase (onset to offset), as measured using the coefficient of variation of the touch phase in subjects with ADHD, was significantly higher than that of subjects in the control group, while no differences were found in other parameters such as the finger tapping rate or the off phase.