The basal ganglia and cerebral cortex are interconnected through two main circuits: the direct pathway and the indirect pathway.
1. Direct Pathway: This pathway facilitates movement initiation. It starts with the cortex initiating a movement command, which is then transmitted to the basal ganglia through the motor cortex. From there, the signal is relayed to the striatum, a part of the basal ganglia. The striatum then inhibits the inhibitory output neurons of the globus pallidus internus (GPi), reducing its inhibitory influence on the thalamus. As a result, the thalamus is disinhibited and can transmit the movement command back to the cortex, allowing the initiation of voluntary movement.
2. Indirect Pathway: This pathway inhibits movement and helps with movement selection and suppression. Similar to the direct pathway, the cortex sends a movement command to the basal ganglia. However, instead of directly exciting the striatum, the signal is first transmitted to the globus pallidus externus (GPe). The GPe inhibits the subthalamic nucleus (STN), reducing its excitatory influence on the GPi. The reduced inhibition on the GPi ultimately results in increased inhibitory output to the thalamus, inhibiting the transmission of movement commands to the cortex, and suppressing unwanted or inappropriate movements.
WHAT ARE THE TWO CIRCUITS BETWEEN BASAL GANGLIA AND CEREBRAL CORTEX
1 answer