Motor cortex control of a complex peripheral apparatus: The neuromuscular evolution of individuated finger movements

Rather than acting as a somatotopic array of upper motor neurons, each controlling a single muscle that moves a single finger, neurons in the primary motor cortex (M1) act as a spatially distributed network of very diverse elements, many of which haveoutputs that diverge to facilitate multiple muscles acting on different fingers. Moreover, some finger muscles, because of tendon interconnections and incompletely subdivided muscle bellies, exert tension simultaneously on multiple digits. Consequently, each digit does not move independently of the others, and additional muscle contractions must be used to stabilize against unintended motion. This biological control of a complex peripheral apparatus initially may appear unnecessarily complicated compared to the independent control of digits in a robotic hand, but can be understood as the result of concurrent evolution of the peripheral neuromuscular apparatus and its descending control from the motor cortex.