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The cerebral cortex (six-layered gray matter) is functionally and anatomically divided into four lobes: frontal (motor, executive function), parietal (somatosensory, spatial), temporal (hearing, memory, semantics), and occipital (vision). Primary sensory areas receive thalamic input; primary motor areas control muscles; association areas integrate information and produce complex cognitive functions. Major white matter tracts (corpus callosum, internal capsule, superior longitudinal fasciculus) enable inter-hemispheric and intra-hemispheric communication.
Use neuroimaging (fMRI, PET) to localize functions in living brains. Study lesion syndromes showing what functions are lost with regional damage. Examine connectivity patterns using diffusion imaging. Compare brain structure across species.
Each brain region has exactly one function / cortex does all thinking and subcortex is primitive / functions don't overlap between regions / the brain is fully mapped.
From your study of neuron morphology, you know the nervous system is built from individual cells — neurons — that communicate via electrochemical signals across synaptic connections. The brain is what happens when ~86 billion of those neurons organize into a dense, layered structure with highly specialized local circuits and long-range projection pathways. Brain structure and functional localization is the study of how that organization maps onto specific mental and behavioral capabilities: which regions do what, and how we know.
The cerebral cortex — the wrinkled gray outer layer — is divided into four lobes with distinct primary functions. The frontal lobe sits anterior (front) and houses the primary motor cortex (which sends movement commands to muscles via the corticospinal tract) and the prefrontal cortex (which handles executive functions: planning, working memory, impulse control, and decision-making). The parietal lobe sits behind the central sulcus and processes somatosensory information — touch, proprioception, and spatial relationships — in the primary somatosensory cortex. The temporal lobe runs along the sides and processes auditory information in primary auditory cortex, and its medial portions include structures critical for memory consolidation and semantic knowledge. The occipital lobe at the rear is devoted to visual processing, organized hierarchically from primary visual cortex (basic edge and orientation detection) to higher visual areas (object recognition, face processing, motion perception).
A crucial organizing principle is the distinction between primary sensory and motor areas and association areas. Primary areas are "input/output terminals" — primary sensory cortex receives thalamic projections from specific sensory organs and produces the raw perceptual signals; primary motor cortex sends output to muscles. Association areas occupy the vast majority of the cortex and perform the integration, interpretation, and combination of information from multiple sources that underlies complex cognition. The temporal-parietal-occipital junction, for instance, integrates information from all three neighboring lobes to support language comprehension, spatial awareness, and attention. This architecture explains why cortical damage is rarely a simple subtraction — removing an area tends to disrupt multiple functions that relied on its integrative contribution.
The evidence for functional localization comes from multiple converging methods. Lesion studies — observing which functions are lost after damage to specific regions — provided the first systematic maps, from Broca's observation that damage to left posterior frontal cortex impairs speech production (Broca's area) to Scoville and Milner's patient H.M., whose bilateral hippocampal removal eliminated new declarative memory formation. Neuroimaging (fMRI, PET) shows which areas increase metabolic activity during specific tasks in living humans. The mature picture from both methods reveals that localization is real but partial: most complex behaviors recruit distributed networks rather than single regions, and the cortex's connectivity through white matter tracts (the corpus callosum connecting hemispheres, the superior longitudinal fasciculus connecting frontal and parietal areas, and many others) is as important as the gray matter regions themselves. Function lives in networks, but networks have nodes — and knowing where the nodes are and what they contribute is the foundation of understanding what happens when they're damaged or disrupted.