Motor sequence learning in dyslexia: Is consolidation the key?

There is uncertainty as to whether the deficits in developmental dyslexia extend beyond the language domain. In the present study, the time course of procedural learning of a motor sequence skill was followed over a 24 hour period. 13 dyslexic adults and 12 control adults matched for age and intelligence were asked to repeat a sequence of finger movements as many times as possible in 30s. They were then trained on the sequence for 400 slow, paced trials and then re-tested for maximum speed. A third testing session was carried out 24hrs after the initial tests (without any further practice). Performance of the two groups did not differ immediately after training, but the dyslexic group showed significant performance deficits initially and immediately after the 24hr break. The latter strongly suggests an impairment in consolidation of learning (a prerequisite for normal automatization), together with normal ability to learn during explicit practice. These findings applied strongly to some dyslexic participants whereas others performed normally, reflecting the considerable heterogeneity of this disorder. The findings provide a novel explanation of why dyslexic children have difficulty learning to read, and may have considerable applied and theoretical implications.