Neokortex

The neocortex, sometimes written as Neokortex in non-English usage, is the part of the cerebral cortex responsible for the brain’s higher cognitive, sensory, and motor functions. It is the largest component of the cerebral cortex in most mammals and is distinguished from older cortical regions such as the archicortex and paleocortex. The neocortex is typically organized into six horizontal layers, from the surface inward: molecular (I), external granular (II) and external pyramidal (III), internal granular (IV), internal pyramidal (V), and multiform (VI). Layer IV is especially prominent in primary sensory areas as a main recipient of thalamic input; other layers distribute intracortical and subcortical connections.

The neocortex is functionally subdivided into primary sensory cortices (visual, auditory, somatosensory), motor and premotor areas, and numerous association cortices that integrate information, support planning, memory, language, and abstract thought. Its neurons, including pyramidal cells and various interneurons, are organized in a columnar fashion that spans multiple layers, enabling specialized processing within local circuits and broad communication across distant regions.

Development and evolution: In mammals, the neocortex arises from the dorsal pallium during embryogenesis and expands considerably in more complex brains, particularly in primates, supporting enhanced sensory processing and cognitive capabilities. Evolution has increased its surface area and connectivity, enabling higher-order functions.

Clinical relevance: Lesions or disease affecting the neocortex can cause sensory deficits, language and speech impairments, apraxia, or cognitive dysfunction. The neocortex also exhibits plasticity, which underlies learning and recovery after injury.