Contraction of time in attention-deficit hyperactivity disorder.

Attention-deficit hyperactivity disorder (ADHD) has been associated with anomalies in dopamine systems. Recent advances in the understanding of the core cognitive deficits in ADHD suggest that dopamine dysfunction might be expressed through shortened time scales in reward-based learning. Here this perspective is extended by the conjecture that temporal span in working memory systems might generally be shortened. As a test of this conjecture the authors focus on the implicit memory system involved in rhythmic movement, assessing the minimum tempo at which rhythmic feeling can be sustained in adults with diagnosed ADHD and in a control group of normal adults. The authors found that people with ADHD do in fact have a rhythm cut-off that is faster in tempo than those without ADHD. This finding is consistent with the idea that impaired dopamine dynamics have systemic consequences for cognitive function, essentially recalibrating the clock that sets the time scale for the subjective experience of temporal events.