telencephalon

The telencephalon is the anterior part of the forebrain (prosencephalon) that gives rise to the cerebral hemispheres. In vertebrates it comprises the cerebral cortex, underlying white matter, and several subcortical structures including the basal ganglia and parts of the limbic system.

During development, the forebrain differentiates into the telencephalon and diencephalon. The telencephalon expands rapidly and envelops the diencephalon, and its ventricular cavities form the lateral ventricles. The major subcortical structures of the telencephalon arise from its ventral and lateral regions, while the cerebral cortex develops into a six-layer structure.

Anatomy: The cerebral cortex is the outer layer of the telencephalon and is divided into lobes—frontal, parietal, temporal, occipital, and insular. Beneath the cortex lie the basal ganglia, consisting of the caudate nucleus, putamen, and globus pallidus, which regulate voluntary movement and procedural learning. The telencephalon also includes limbic structures such as the hippocampus and amygdala, which support memory and emotion, connected through regions like the cingulate and parahippocampal gyri. The olfactory cortex represents an older part of the telencephalon and connects with limbic areas involved in emotion and memory.

Function: The telencephalon supports higher cognitive functions, perception, planning, and language in the dominant hemisphere, as well as voluntary motor control through corticostriatal circuits. It processes sensory information, underpins memory formation and retrieval, and participates in emotion and social behavior. Abnormalities in telencephalic regions can lead to aphasia, memory impairment, movement disorders, or seizures depending on the site of pathology.