Midbrain

The midbrain is the short middle division of the brain, positioned between the forebrain and the hindbrain. It lies between the thalamus and hypothalamus region of the forebrain above and the pons of the hindbrain below, forming a bridge between these two larger portions of the brain.

A narrow channel called the cerebral aqueduct runs through the midbrain. This canal is part of the fluid-filled cavity system of the brain and passes lengthwise through this region.

On its upper, or dorsal, surface the midbrain bears a distinctive set of structures. This dorsal portion is made up mainly of four rounded swellings, or lobes, known together as the corpora quadrigemina. These paired swellings are the most noticeable external feature of the midbrain. …