Neuroscience Lecture: Basal Ganglia

Introduction to the Basal Ganglia

• Location: Located deep within the cerebral hemisphere and brainstem.
• Components:
  • Caudate nucleus and putamen (collectively known as the striatum).
  • Globus pallidus and substantia nigra (each comprising multiple nuclei).
  • Subthalamic nucleus.

Functions

• Known for facilitating movement.
• Involved in various non-movement functions.

Information Flow in the Basal Ganglia

• Input: Primarily from the cerebral cortex to the caudate nucleus or putamen.
• Output: From the globus pallidus and substantia nigra to:
  • The cerebral cortex via the thalamus.
  • Nuclei in the brainstem.

Role in Movement

• Does not cause movement independently.
• Influences other brain regions like the motor cortex.
• Hypothesis: The basal ganglia have circuits that facilitate and inhibit movement.
  • Direct pathway: Facilitates movement.
  • Indirect pathway: Inhibits movement.

Direct Pathway

• Signals from the cortex initiate movement.
• Follow a circuit known as the direct pathway.
• Leads to the silencing of neurons in the globus pallidus.
• Lifts inhibition on the thalamus, allowing movement.

Indirect Pathway

• Involves the subthalamic nucleus.
• Leads to stronger inhibition of unnecessary movements.
• The balance between the direct and indirect pathways is thought to achieve smooth movement.