[8] The dorsal telencephalon then forms two lateral telencephalic vesicles, separated by the midline, which develop into the left and right cerebral hemispheres.

The primary sensory areas of the cerebral cortex receive and process visual, auditory, somatosensory, gustatory, and olfactory information.

The olfactory bulb, responsible for the sense of smell, takes up a large area of the cerebrum in most vertebrates.

Explicit or declarative (factual) memory formation is attributed to the hippocampus and associated regions of the medial temporal lobe.

This association was originally described after a patient known as HM had both his left and right hippocampus surgically removed to treat chronic [temporal lobe epilepsy].

In the most primitive vertebrates, the hagfishes and lampreys, the cerebrum is a relatively simple structure receiving nerve impulses from the olfactory bulb.

In cartilaginous and lobe-finned fishes and also in amphibians, a more complex structure is present, with the cerebrum being divided into three distinct regions.

The lowermost (or ventral) region forms the basal nuclei, and contains fibres connecting the rest of the cerebrum to the thalamus.

The cerebrum remains largely devoted to olfactory sensation in these animals, in contrast to its much wider range of functions in amniotes.

The inner surfaces of the lateral and ventral regions of the cerebrum bulge up into the ventricles; these include both the basal nuclei and the various parts of the pallium and may be complex in structure, especially in teleosts.

In reptiles, the paleopallium is much larger than in amphibians and its growth has pushed the basal nuclei into the central regions of the cerebrum.

The paleopallium is pushed to the ventral surface of the brain, where it becomes the olfactory lobes, while the archipallium becomes rolled over at the medial dorsal edge to form the hippocampus.

The increased size of bird brains was classically attributed to enlarged basal ganglia, with the other areas remaining primitive, but this view has been largely abandoned.

[11] Birds appear to have undergone an alternate process of encephalization,[12] as they diverged from the other archosaurs, with few clear parallels to that experienced by mammals and their therapsid ancestors.