Corticospinal tract fiber origins

Question 1

Where do Corticospinal tract fibers originate in brain?

Answer 1

60% a come from primary motor cortex, premotor areas, and supplementary motor areas. The remainder originates from primary sensory areas, the parietal cortex, and the operculum, so could have a positive Babinski sign (indicating upper motor neuron lesion) in pt with lesion at primary somatosensory cortex of parietal lobe.