Impaired procedural learning after damage to the left supplementary motor area

Ackermann et al have recently reported on procedural learning in a patient with a lesion of the left mesiofrontal cortex. The patient had no deficit when tracking a visual target by his right hand. However, the patient's performance was severely impaired in a mirrored tracking task. It was concluded that the finding confirms "previous PET results (the reader is referred to studies by Seitz et al2 and Grafton et al I) indicating the supplementary motor area to be a part of circuits mediating visuomotor skill acquisition." In the study of Seitz et al2 subjects were taught a sequence of finger to digit oppositions before PET. PET was performed during initial learning of the sequence, advanced learning, and during skilled performance. They found activation of the supplementary motor area during initial learning as well as during skilled performance and no evidence for a specific inolvement of the supplementary motor area in motor learning. Grafton et a13 employed a pursuit rotor task. Activation in the posterior part of the supplementary motor area was found to increase with the level of skilled performance. There was no indication of a role of the supplementary motor area in