part of part of has part has part characteristic of has modifier neuron Upper motor neuron dysfunction A functional deficit of the tract that conveys nervous impulses from the motor cortex of the brain to the spinal cord. The corticospinal tract mediates discrete voluntary skilled movements. Clinical features of corticospinal tract dysfunction may include spasticity and weakness, particularly affecting the lower limbs, as well as hyperreflexia, clonus at the ankles and knees, and extensor plantar responses (Babinski response). Abnormal cellular physiology Abnormal central motor function abnormal decreased functionality primary motor cortex