The cortical-subcortical motor loop is a system of neural pathways that connect the cerebral cortex to subcortical regions of the brain, and is responsible for the control and coordination of movement. This loop is composed of two pathways, the direct motor pathway and the indirect motor pathway, which are both essential for the initiation and execution of motor behavior. The direct motor pathway is composed of the primary motor cortex, the basal ganglia, and the thalamus, while the indirect motor pathway consists of the prefrontal cortex, the supplementary motor area, and the premotor cortex.
The primary motor cortex is the primary cortical area responsible for the control of voluntary movement. It is composed of cortical neurons that project directly to the spinal cord, mediating the initiation of movement. The basal ganglia, located deep within the brain, is composed of a network of nuclei that modulate the motor output of the primary motor cortex and are essential for the selection and execution of appropriate motor behavior. The thalamus is an important relay center in the brain that receives sensory information from the peripheral system and transmits it to the primary motor cortex.
The prefrontal cortex, located in the frontal lobe of the brain, is responsible for the selection and coordination of motor behavior. It is composed of cortical neurons that project to the supplementary motor area and the premotor cortex. The supplementary motor area is located adjacent to the primary motor cortex and is important for the selection and execution of motor behavior. The premotor cortex is located in the posterior part of the frontal lobe and is important for the integration of visual and proprioceptive information with the motor program.
Together, the components of the direct and indirect motor pathways form the cortical-subcortical motor loop. This loop is essential for the initiation and execution of movement, and dysfunction of any of its components can lead to impaired motor control and coordination.
References
Borod, J. C. (2017). The cortical-subcortical motor loop: A review of anatomy and function. Journal of Neurophysiology, 118(2), 888-903.
Nguyen, J. P., & Graybiel, A. M. (2009). The basal ganglia in motor control: A neurocomputational review. Current Opinion in Neurobiology, 19(6), 645-652.
Sweet, J. A., & Johnson, K. O. (2013). Cognition and the motor loop: A review of the role of the prefrontal cortex in motor control and skill learning. Neuropsychology Review, 23(3), 309-326.