The Substantia Nigra Is

The substantia nigra is:

A) an area of the midbrain that is involved in motor control and that contains a large concentration of dopamine-producing neurons.
B) the brain location that has shown the greatest degree of neurogenesis in studies with rats and primates.
C) the primary communication link between the two hemispheres of the cerebral cortex.
D) the point at which motor signals cross over from one side of the brain to the opposite side of the body.