Brain anatomy, illustration. The front of the brain is at left. This view is a midline sagittal section, with the labelled structures in the hindbrain including the pons and the reticular formation (green). Next to the pons is the fourth ventricle and the opening into the subarachnoid space. Above these, forming part of the limbic system, are the hypothalamus and thalamus. Above these, connecting the two halves of the brain, is the corpus callosum.