This image shows some of the major structures visible on the ventral surface of the frog brain. Note the previously mentioned olfactory lobes (2) and associated olfactory nerves (1). On the ventral surface of the diencephalon, the two optic nerves (4) cross to form the optic chiasma and from there extend to the optic tracts (5) that carry impulses to the optic lobes on the dorsal surface of the brain.

Note: The olfactory and optic nerves are but two of the 10 pairs of cranial nerves possessed by all amphibians.

Posterior to the optic chiasma is a ventral outgrowth of the diencephalon called the pituitary gland, or hypophysis (6). This endocrine gland (which actually consists of two major subdivisions with different embryonic origins) regulates many body functions including in amphibians, changes in skin color. Anterior to the optic chiasma are the large cerebral hemispheres (3) of the telencephalon. Once again, the medulla oblongata (7) of the myelencephalon can be seen, along with the cranial nerves (shown in yellow on the model) that arise from this most posterior portion of the brain.