Role of the Basal Ganglia
The basal ganglia play a complex and integral role in the control of movement:
- Selecting and maintaining purposeful motor activity while suppressing unwanted or useless movement.
- Helping monitor and coordinate slow, sustained contractions related to posture and support.
- Inhibiting muscle tone throughout the body (proper muscle tone is normally maintained through a balance of excitatory and inihibtory inputs to the neurons that inervate skeletal muscle).
Compare the basal ganglia’s functions with the symptoms of Parkinson’s disease.
Anatomy of the Basal Ganglia
The basal ganglia consists of the striatum, the globus pallidus and the subthalamic nucleus.
The striatum is the target of cortical input to the basal ganglia and can be divided into the caudate nucleus and the putamen.
The globus pallidus is the source of output to the thalamus and can be divided into an internal and external segment.
The substantia nigra is a midbrain structure that is reciprocally connected with the basal ganglia of the forebrain.
The Basal Ganglia and Movement
The command to initiate movement is implemented with the participation of subthalamic input to the SMA and PMC arising from the ventral lateral (VL) nucleus of the dorsal thalamus. The input to this part of the VL arises from the basal ganglia.
The basal ganglia, in turn, receive input from the cerebral cortex, particularly the frontal, prefrontal and parietal cortex. Hence information cycles from the cortex, to the basal ganglia and thalamus, and back to the cortex again, forming a loop that functions in the selection and initiation of willed movements.
Sources: Parkinson’s Disease site from Evergreen State College; Bear, M. F., Connors, B.W. & Paradiso M. A., Neuroscience: Exploring the Brain, Second Edition, 351 West Camden St., Baltimore, MD: Lippincott Williams & Wilkins, 2001, pp 473-482