Attention deficit and hyperactivity disorder disrupts selective mechanisms of action.

Objective: People with attention deficit and hyperactivity disorder (ADHD) present attentional and emotional deficits and show paradoxical qualities such as hyperfocus. Previous studies have reported errors, slowness, and reaction time (RT) variability using eye movements. This study aimed to explore the underlying mechanisms of ADHD further.

Methods: Thirty French children and teenagers, 15 with ADHD and 15 neurotypical (NT), underwent a saccadic eye movement task. We conducted conventional analysis (movement duration, precision, velocity, RT) and Bayesian analysis.

Results: Saccade duration and velocity failed to differentiate the two groups, whereas amplitude was higher in ADHD than in NT participants. Saccade RT and variability were higher in ADHD than in NT participants. In the Bayesian analysis, ADHD altered the main distribution of saccades and of early saccades but did not influence the express saccade triggering.

Conclusions: ADHD disrupts two mechanisms of action: it reduces the gain of the decision signal, thus explaining slowness and variability; it quickens the decision process of early responses at the origin of short-latency but controlled movements.

Significance: These premises and their interconnections explain previous observations and support the striatal-frontal wiring of ADHD, thus explaining ADHD complexity in its negative and positive manifestations.