Atypical acquisition and atypical expression of memory consolidation gains in a motor skill in young female adults with ADHD.

Individuals with ADHD often show performance deficits in motor tasks. It is not clear, however, whether this reflects less effective acquisition of skill (procedural knowledge), or deficient consolidation into long-term memory, in ADHD. The aim of the study was to compare the acquisition of skilled motor performance, the expression of delayed--consolidation phase--gains and retention, in persons with and without ADHD. Thirty-two participants, 16 with ADHD, were trained on a sequence of finger movements using a well-established training protocol, and tested before training and immediately, 24h and 2 weeks after training. Both groups showed similar within-session gains in speed; additional, delayed gains were expressed at 24h, but less robustly in ADHD, and at 2 weeks post-training. However, while controls showed significant delayed gains in accuracy at 24h and 2 weeks post-training, accuracy deteriorated in ADHD from pre-training to 24h post-training and was only at pre-training levels by 2-weeks post-training. Our results demonstrate a latent memory consolidation phase in motor sequence learning, expressed as delayed gains in speed and a much delayed recovery of pre-training accuracy, in individuals with ADHD. However, both the acquisition and memory consolidation of motor skills are atypical in ADHD.