Dissociation between the procedural learning of letter names and motor sequences in developmental dyslexia

Motor sequence learning has been studied extensively in Developmental dyslexia (DD). The purpose of the present research was to examine procedural learning of letter names and motor sequences in individuals with DD and control groups. Both groups completed the Serial Search Task which enabled the assessment of learning of letter names and motor sequences independently of each other. Control participants learned both the letter names as well as the motor sequence. In contrast, individuals with DD were impaired in learning of the letter names sequence and showed a reliable transfer of the motor sequence. Previous studies proved that motor sequence learning is impaired in DD. The present study demonstrated that this deficit is more pronounced when the task to be learned involves linguistic units. This result implies that the procedural learning system of language is more deficient than the motor procedural learning system in individuals with DD. The dissociation between motor and letter names sequence learning in those with DD also implies that the systems underlying these two tasks are separable.