FIGURE 11-9 Left-Hemisphere Corticospinal Tract Nerve fibers descend from the left-hemisphere motor cortex to the brainstem, where the tract branches into the spinal cord. The lateral tract crosses the brainstem’s midline, descending into the right side of the spinal cord to move limb and digit muscles on the body’s right side. The anterior tract remains on the left side to move muscles at the body’s midline.