Telencephalon; Brain

The telencephalon (commonly referred to as the brain) is a subdivision of the prosencephalon, along with the diencephalon, and constitutes the most rostral part of the encephalon.

During embryonic development, the telencephalon forms through the division of the prosencephalon, which itself arises from the anterior neural tube. The prosencephalon initially differentiates into three primary vesicles: the prosencephalon, mesencephalon, and rhombencephalon. The prosencephalon subsequently subdivides into the telencephalon (which gives rise to the cerebral hemispheres) and the diencephalon.

The telencephalon consists of two cerebral hemispheres connected by several commissures, including the corpus callosum and the rostral commissure, as well as by the lamina terminalis.

Each cerebral hemisphere includes:

• Rhinencephalon (ventral): the olfactory region, including the olfactory bulb, olfactory tract, piriform lobe, parahippocampal gyrus, septum, and amygdala. The rhinencephalon is involved in olfaction, memory formation, and emotional behavior.

• Lateral ventricle: filled with cerebrospinal fluid, which communicates with the third ventricle of the diencephalon via the interventricular foramen.

• Cerebral cortex (pallium): covering the dorsolateral surface of the hemisphere and subdivided into:

  • Paleopallium

  • Archipallium

  • Neopallium: the most developed in mammals, corresponding to the neocortex, responsible for sensory, associative, and motor functions. Specialized areas include primary sensory regions, associative regions, and motor areas (premotor and primary motor).

• Striatum (basal nuclei): including the caudate, putamen, pallidum, nucleus accumbens, and claustrum. The basal nuclei regulate the selection and execution of voluntary movements.

The telencephalon is involved in numerous cognitive, sensory, motor, olfactory, and emotional functions. The rhinencephalon is particularly implicated in emotional behavior and the limbic system, whereas the neopallium mediates perception, sensory integration, planning, and motor execution. Commissures, particularly the corpus callosum, enable the integration of information between the two hemispheres.

In mammals, the telencephalon represents by far the largest and most evolutionarily advanced part of the nervous system.