<P> During embryonic development, the midbrain (also known as the mesencephalon) arises from the second vesicle of the neural tube, while the interior of this portion of the tube becomes the cerebral aqueduct . Unlike the other two vesicles - the forebrain and hindbrain - the midbrain does not develop further subdivision for the remainder of neural development . It does not split into other brain areas . while the forebrain, for example, divides into the telencephalon and the diencephalon . </P> <P> Throughout embryonic development, the cells within the midbrain continually multiply; this happens to a much greater extend ventrally than it does dorsally . The outward expansion compresses the still - forming cerebral aqueduct, which can result in partial or total obstruction, leading to congenital hydrocephalus . </P> <P> The mesencephalon is considered part of the brainstem . Its substantia nigra is closely associated with motor system pathways of the basal ganglia . The human mesencephalon is archipallian in origin, meaning that its general architecture is shared with the most ancient of vertebrates . Dopamine produced in the substantia nigra and ventral tegmental area plays a role in movement, movement planning, excitation, motivation and habituation of species from humans to the most elementary animals such as insects . Laboratory house mice from lines that have been selectively bred for high voluntary wheel running have enlarged midbrains . The midbrain helps to relay information for vision and hearing . </P>

Where is the midbrain located and what is its function