The cerebral cortex is the thin, folded outer layer of the brain. It is the seat of the higher functions that distinguish human cognition—perception, voluntary movement, language, reasoning, and planning.

In humans the cortex is deeply convoluted, greatly increasing its surface area within the confines of the skull. It is divided into four lobes on each side: frontal, parietal, temporal, and occipital. Primary sensory and motor areas occupy specific regions; the much larger remaining territory consists of association cortex that integrates information and supports complex mental activity. The two hemispheres are specialized to a degree—language is typically left-lateralized—yet they remain in constant communication via the corpus callosum.

Cortical thickness and the integrity of its connections change across the lifespan and are affected by experience, disease, and injury. Neuroimaging has made it possible to watch the cortex at work during specific tasks, revealing distributed networks rather than isolated centers for most psychological functions.

When we speak of the mind’s most flexible and distinctively human capacities, we are largely speaking of the cerebral cortex.