Which tract carries the majority of input to the internal capsule?

The internal capsule is a critical structure in the brain that serves as a major pathway for communication between the cortex and other areas of the brain, including the brainstem and spinal cord. Among the various tracts that pass through the internal capsule, the corticospinal tract is the predominant one. It consists of upper motor neurons that originate in the motor cortex and descend to synapse on lower motor neurons in the spinal cord, playing a crucial role in voluntary motor control.

The corticospinal tract is involved in carrying motor commands that dictate voluntary movement, and its large volume compared to other tracts reflects its significance in executing these commands. Therefore, it constitutes the majority of the input routed through the internal capsule.

In contrast, while other tracts like the spinothalamic, vestibulospinal, and rubrospinal tracts indeed contribute to the overall function of the nervous system, they do not represent the primary input to the internal capsule in terms of volume or significance. The spinothalamic tract, for instance, is primarily responsible for transmitting pain and temperature sensations to the thalamus but does not carry motor signals like the corticospinal tract. The vestibulospinal tract is involved in balance and posture, and the rubro