[7] The two major input structures of the circuit are the striatum and the subthalamic nucleus (STN).

[1][8] The parallel CBGTC loops have been segregated according to the functions of associated cortical regions.

[9] The loop has also been divided into limbic, associative, oculomotor, and motor circuits[4] to explain the role of dopamine in the basal ganglia on motivational states.

[2] One review supported the idea that the cortex was involved in learning actions regardless of their outcome, while the basal ganglia was involved in selecting appropriate actions based on associative reward based trial and error learning.

For example, in Parkinson's disease, degeneration of dopaminergic neurons leading to decreased activity of the excitatory pathway is thought to result in hypokinesia,[15] and in Huntington's disease, degeneration of GABAergic neurons driving the inhibitory pathway is thought to result in the jerky body movements.

[9] In OCD, the loop may be dysfunctional, with an imbalance between the indirect and direct pathways resulting in unwanted thoughts, getting "stuck".

[16][17] The CBGTC loop model has been criticized as oversimplified and too rigidly applied, given evidence of anatomical and functional overlap and interactions between the direct and indirect pathways.