Chapter 5 Summary

Motor control is hierarchical. Lower motor neurons in the spinal cord and brainstem are the final common pathway for the motor commands that determine behaviors arising from skeletal muscle movements, and they are thus the effectors for many cognitive processes. Upper motor neurons in the primary motor cortex and cortical premotor areas issue motor commands that activate local circuits and lower motor neuron pools to achieve more specific behavioral goals.
Descending pathways from the motor and premotor cortices are important in planning and initiating voluntary, goal-directed sequences of movement, especially for learned motor skills. Of special relevance here, these circuits are sensitive to motivational goals that guide movement selection.
The motor and premotor cortices are under the modulatory influence of the basal ganglia and cerebellum. The basal ganglia control the initiation and stopping of movements and contribute to motor skill learning, the production of movement sequences, and the selection of movements that satisfy behavioral goals. The cerebellum acts further to coordinate movements by correcting unanticipated errors in ongoing motor processing in the motor and premotor cortices.
Acting together, the various motor circuits mediate production of the complex intrinsic and learned sequences of movement that are characteristic of human motor behaviors that express cognitive goals.
Damage to any of these motor control circuits results in specific disruptions in movement planning, initiation, or coordination. Damage to some of these circuits—the basal ganglia and cerebellum in particular—also causes deficits in a variety of cognitive functions.