There is no single neural locus for learning, rather a multiplicity of brain structures are involved in motor control. This page reviews five main brain structures and their role in motor control as well as other structures involved in motor learning.

Main Structures Involved in Motor Control

1. Motor tracts are responsible for transferring information from the brain to the muscles.  Muscle contraction is caused by an impulse from from a neuron at the neuromuscular junction.  Hence for muscles to move information must be relayed from the nervous system to the muscles.  Four pathways are involved in this: (a) the corticospinal, (b) corticobulbar, (c) ventromedial and (d) rubrospinal pathways.

A. Corticospinal Tract

Links the cortex to the spinal cord
Lateral tract controls distal limbs

Ventral tract controls the muscles of trunk and upper leg

Connects motor cortex to cranial nerves in the pons
Important in tongue and face innervation

Links brainstem to the spinal cord, with indirect linkages to the primary motor cortex
Primary function is to control movements of the trunk and proximal limb muscles, especially in posture

Important for coordinating eye movements with those of the head and trunk.

Originates in the midbrain and has connections with the motor cortex, cerebellum and spinal cord.
Modulates motor movements

2.  The cerebellum plays an important role in the modulation of motor movements and in the learning of motor skills.  It is thought to improve the coordination of muscles and to maintain equilibrium.  The cerebellum also contributes to generating and planning movements.

3. The basal ganglia consist of three nuclei, the caudate nucleus, putamen and globus pallidus.  The putamen and caudate receive input from all regions of the cerebral cortex and the substantia nigra.  The globus pallidus send information to the thalamus.  The basal ganglia have multiple roles in motor control including:

"Setting" the motor system with regard to posture
Preparation for voluntary movements

Act as an autopilot for well-learned behaviors.

Involved in motor planning and learning

Plays a role in cognitive components of learning

Facilitates ongoing action

Suppresses unwanted movement

A. Primary Motor Cortex

Relays information to the spinal cord to enable muscle control
Receives input from several areas of the cortex

Activated during tasks requiring complicated motor sequencing
Commands are thought to be programmed in the SMA

Specifically involved in complex tasks

Implicated for control and planning of movements
May play a role in linking motor and cognitive behavior

Most active when novel responses are required

Other Important Structures

Several other structures are necessary for a motor skill to be carried out.  The thalamus is important for organizing and directing incoming information to other regions of the brain.  It also modifies information descending from the cortex.

The spinal cord is the information highway relaying information to and from the brain.  It has several ascending and descending pathways.  It also contains motor programs for a number of common behaviors (i.e. walking) and reflex pathways.  The cerebral cortex turns on the appropriate motor program in the spinal cord.