hyperpallium

The hyperpallium is a major region of the avian brain, located in the dorsal telencephalon as part of the pallium. It lies above the mesopallium and nidopallium and is part of the dorsal pallial structures that form the avian pallium. In birds, the hyperpallium is a prominent laminated area that has been studied for its role in higher-order processing, and it is often described as a functional analogue to parts of the mammalian neocortex rather than a direct homolog.

Anatomically, the hyperpallium includes the hyperpallium densocellulare (HD) and related subdivisions, which together create a layered organization within the dorsal pallium. The term is sometimes used within the broader concept of the dorsal ventricular ridge (DVR), a neural complex that encompasses several pallial regions. The precise borders and subdivisions can vary among species, but the hyperpallium is consistently recognized as a major, relatively laminated pallial area involved in processing sensory and cognitive information.

Functionally, the hyperpallium participates in higher cognitive processes, including associative learning, sensory integration, and aspects of spatial and visuospatial processing. It has been investigated for its role in tasks related to memory, perception, and, in some species, aspects of vocal learning and social behavior. While the avian hyperpallium shares functional parallels with the mammalian neocortex, it reflects a distinct evolutionary arrangement of neural circuits.

Evolutionarily, the hyperpallium illustrates how birds achieve complex cognition through a pallial organization that is morphologically different from the mammalian cortex but capable of analogous processing.