Cognitive control of sequential behavior

Movement can be considered as a crucial aspect of any living being, and has sometimes been considered as the main reason for the actual coming into existence of cognition. Most actions we perform in everyday life consist of series (sequences) of simple movements, by which we are able to attain fluent execution of more complex movement patterns. In this thesis, the mechanisms underlying motor sequence learning, as studied with the discrete sequence production (DSP) task, were investigated by focusing on response times, error rates and measures derived from the electroencephalogram (EEG). Results show that sequence learning in the DSP task is initially based on stimulus-response learning, but with practice sequence learning in the DSP task becomes based on multiple representations, which develop with practice. These representations can be effector dependent and effector independent. Measured derived from the EEG suggest the involvement of a general motor representation during the preparation of sequences, which is effector independent. The activity of this general motor representation decreases with practice, which suggests that with unfamiliar sequences response specifications are unknown and have to be filled in, whereas with familiar and mirrored sequences more response specifications are fixed in the general motor representation. Finally, to learn more about sequence learning we studied the differences in sequence learning in people with dyslexia. Dyslexics are thought to have difficulties with skill automatization, such as motor sequence learning. In this thesis it was shown for the first time that dyslexics were slowed in discrete sequence learning, as compared with controls. This agrees with the automatization deficit in dyslexics suggested by the cerebellar-deficit hypothesis.