At what location does the corticospinal tract decussate?

The corticospinal tract decussates, or crosses over, at the level of the medulla oblongata. This crossing occurs in the lower portion of the medulla, specifically at the junction where the medulla meets the spinal cord. Approximately 90% of the fibers of the corticospinal tract cross over to the opposite side at this location, which is critical for the functioning of voluntary motor control. This means that the left side of the brain controls the right side of the body and vice versa.

Understanding this decussation is important for clinical assessments and understanding motor pathway injuries. The other locations mentioned in the options do not relate to the crossing of the corticospinal tract: the spinal cord primarily contains reflex pathways, the optic chiasm is involved in visual processing, and the lateral geniculate nucleus processes visual signals, not motor control.