Comparison of neuronal activity in the supplementary motor area and primary motor cortex.

Neuronal activity in the supplementary motor area (SMA) and primary motor cortex (MI) have been compared in many experiments during performance of many different motor tasks. On one hand, the activity in both areas may appear similar, especially when the motor task is simple. On the other hand, if the motor tasks are more demanding, neuronal activity in the SMA exhibits a variety of complex relationship to many different aspects of motor behavior, while the activity in MI is mostly related to execution of motor task itself. Of particular interest is the neuronal activity in the SMA during preparation and execution of motor tasks when no external cues for the retrieval of appropriate motor act is available. Temporal sequencing of multiple movements is a typical example of the kind of motor task that requires profound activity in the SMA.