mesopallium

The mesopallium is a region of the pallium in the brains of birds and some reptiles, and is considered a major component of the dorsal pallial complex within the telencephalon. In many sauropsids it forms part of the dorsal ventricular ridge (DVR), a broad cortical-like area involved in higher-order processing.

Anatomy and connections in birds place the mesopallium as a substantial sheet of pallial tissue that interfaces with nearby pallial regions such as the hyperpallium, nidopallium, and arcopallium. It receives a range of sensory inputs from thalamic and midbrain pathways and projects to multiple higher-order pallial areas, supporting integration across sensory modalities and coordination of complex behaviors. The exact boundaries and subdivisions of the mesopallium can vary among species, and researchers sometimes describe anterior and posterior or medial and lateral subdivisions depending on the lineage studied.

Functionally, the mesopallium is associated with higher-order sensory processing, multisensory integration, learning, and memory. In songbirds, neural activity in portions of the mesopallium is linked to song perception and production, illustrating its role in complex cognitive tasks and communication. Across sauropsids, the mesopallium participates in cortical-like processing that supports adaptive behavior, though precise functional specializations differ by species.

Development and evolution: the mesopallium develops from pallial progenitor zones during embryogenesis and is regarded as a conserved component of the dorsal pallium across sauropsids, with considerable variation in structure and connectivity. In mammals, there is no widely recognized direct homolog of the avian mesopallium, and the term is largely restricted to birds and related reptiles.

See also: dorsal ventricular ridge, hyperpallium, nidopallium, arcopallium.