In this video I discuss the group of structures known as the basal ganglia, which includes the caudate, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. I describe the role of the basal ganglia in facilitating movement, and I briefly discuss the direct and indirect pathways, two circuits in within the basal ganglia that are thought to promote and inhibit movement, respectively.

For an article (on my website) that explains the basal ganglia more in-depth, click this link: https://neuroscientificallychallenged.com/posts/what-are-basal-ganglia

TRANSCRIPT:

Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the basal ganglia.

The basal ganglia are a group of structures found deep within the cerebral hemispheres and the brainstem that include the caudate, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. The caudate and putamen are often referred to collectively as the striatum, and the globus pallidus and substantia nigra are each made up of multiple nuclei. Although there are a variety of nonmotor functions associated with the basal ganglia, they are best known for their role in facilitating movement.

Much of the information the basal ganglia receives comes from the cerebral cortex and travels first to the caudate or putamen, the main input nuclei of the basal ganglia. The globus pallidus and substantia nigra are the main output nuclei, and they send projections out from the basal ganglia to the cerebral cortex, mostly by way of the thalamus, as well as to nuclei in the brainstem.

Activity in the nuclei of the basal ganglia doesn’t cause movement independently, but instead the basal ganglia influence activity in other areas of the brain like the motor cortex to affect movement. The ways in which the basal ganglia do this are not fully understood, but one hypothesis is that there are different circuits in the basal ganglia that promote and inhibit movement, respectively. According to this model, the main output of the basal ganglia is inhibitory and the neurons in the globus pallidus are constantly inhibiting the thalamus to prevent unwanted movements.

When a signal to initiate movement is sent from the cortex to the basal ganglia it follows a circuit in the basal ganglia known as the direct pathway, which leads to the silencing of neurons in the globus pallidus. This frees the thalamus from the inhibitory effects of the globus pallidus and allows movement to occur. There is also a circuit within the basal ganglia called the indirect pathway, which involves the subthalamic nucleus and leads to increased suppression of unwanted movements. It is thought that a balance between activity in these two pathways may allow for smooth movement.

Reference:

Mink JW. The basal ganglia: focused selection and inhibition of competing motor programs. Prog Neurobiol. 1996 Nov;50(4):381-425.

Purves D, Augustine GJ, Fitzpatrick D, Hall WC, Lamantia AS, McNamara JO, White LE. Neuroscience. 4th ed. Sunderland, MA. Sinauer Associates; 2008.