Psychology › Brain & biology
Brain regions and localization of function
Since Broca, 1861· Concept
Well replicatedStrong, repeated evidence.
The principle that different parts of the brain specialize in different jobs, such as speech, vision, movement or memory.
See it on the Psychology map →What it says
Franz Gall's phrenology (around 1800) claimed skull bumps revealed traits: wrong, but it planted the idea of localization. Convincing evidence came in 1861, when Paul Broca linked a patient's loss of speech to damage in the left frontal lobe. Then came maps of movement and touch strips across the cortex, Wilder Penfield's stimulation of awake surgery patients' brains, and brain imaging. The modern view: regions specialize, but almost every ability depends on networks linking many areas.
Why it matters
It underlies neurology, brain surgery and imaging, and it dispels myths: the claim that we use only 10% of our brains is false.
Think of it like
Like a mixed-use building: each floor has its main tenant, but nothing works without the shared elevators, risers and wiring linking them.
The evidence
Status: well replicated. Brain-injury patients, electrical stimulation during surgery, animal studies and brain imaging agree on the broad map.
Open questions
How localized versus distributed functions really are; imaging studies are prone to over-claiming, and how networks produce thought is still unknown.
Inside this (5)
Connections (7)
▸Neurons and synapses cluster into Brain regions and localization of functionWell replicated
The connection
Neurons with similar jobs bunch together and wire into circuits: visual cortex at the back, movement strips across the top, the hippocampus deep in the temporal lobe. The wrinkled cerebral cortex, a sheet a few millimeters thick, holds about 16 billion neurons; the small cerebellum holds about 69 billion. Regions work in networks, not alone.
Who showed it and when
Korbinian Brodmann mapped 52 numbered cortical areas by cell structure in Berlin in 1909; Wilder Penfield's surgeries in Montreal, 1930s–1950s, mapped body areas by electrical stimulation.
The evidence
Microscopic cell maps, stimulation during surgery and injury cases; a 2016 map by Matthew Glasser's team identified 180 areas per hemisphere from MRI data.
Open questions
How best to divide the brain is still debated: maps range from dozens to hundreds of areas, and borders differ between individuals.
▸The amygdala: threat detection and fear is a key structure among Brain regions and localization of functionWell replicated
The connection
The amygdala is a classic case of localized function. In 1930s experiments, monkeys whose temporal lobes, amygdala included, were removed lost their fear of snakes and people, and human patients with damage show blunted fear. Yet it works in a network with the prefrontal cortex, hippocampus and hypothalamus, which regulate and act on its alarms.
Who showed it and when
Named from the Greek word for almond in the early 1800s; key lesion studies by Heinrich Klüver and Paul Bucy, University of Chicago, 1937–1939.
The evidence
Animal lesion and recording studies, rare human patients such as S.M., and brain imaging all point to the same structure.
Open questions
Whether it is a 'fear center' or a broader detector of anything important; the old 'limbic system' grouping is now seen as loose.
▸Prefrontal cortex: planning and self-control matures last among Brain regions and localization of functionWell replicated
The connection
The brain matures roughly back to front: sensory and movement areas first, prefrontal areas last. Unused connections are pruned and wiring is insulated (myelinated) into the twenties, which helps explain why teenagers can reason well yet take impulsive risks, especially with peers around.
Who showed it and when
Long-term MRI studies at the US National Institute of Mental Health led by Jay Giedd, scanning children repeatedly from the 1990s; a key paper appeared in 2004.
The evidence
Repeated scans of the same children over about a decade, confirmed by larger later studies, show this back-to-front sequence.
Open questions
The popular 'brain matures at 25' line is a simplification: development varies by person and continues past 25, and how much brain timing explains teen behavior is debated.
▸Hippocampus: forming new memories is a textbook case of Brain regions and localization of functionWell replicated
The connection
The hippocampus is a textbook case of a region with a specific job. When it is damaged, people lose the ability to form new memories of events while intelligence, old skills and short-term memory survive: proof that memory is not one thing but several systems housed in different places.
Who showed it and when
Named in 1587 by Bologna anatomist Giulio Cesare Aranzi for its seahorse shape; its memory role was established in 1957 by William Scoville and Brenda Milner.
The evidence
Amnesia cases such as H.M., recordings of place cells in rats (1971) and brain imaging all converge on its role.
Open questions
Whether old memories eventually stop depending on the hippocampus, or always need it to be recalled vividly, is still debated.
▸Split-brain experiments (Sperry, Gazzaniga) showed hemisphere specialization in Brain regions and localization of functionWell replicated
The connection
Split-brain patients showed that the two hemispheres, normally sharing information instantly, have different strengths. The left usually handles speech and grammar; the right is better at faces, spatial layout and some emotional cues. Cutting the link exposed this division of labor, extending the localization story that began with Broca's speech area.
Who showed it and when
California Institute of Technology, Pasadena, from 1962: Roger Sperry and Michael Gazzaniga, with surgeons Joseph Bogen and Philip Vogel, studying epilepsy patients.
The evidence
Repeated tests on a few dozen patients over decades, Sperry's 1981 Nobel Prize, and matching results from brain imaging and from numbing one hemisphere at a time (the Wada test).
Open questions
Specialization is relative: both hemispheres contribute to most abilities, and some left-handers have language on the right or both sides.
▸Brain imaging: EEG, PET and fMRI maps activity in Brain regions and localization of functionWell replicated
The connection
Before imaging, a region's job was inferred from injuries or autopsies. PET and fMRI let researchers watch healthy brains as people read, remember or decide, showing which areas work harder. That confirmed classic regions like Broca's area, found new ones like a patch specialized for faces, and showed that tasks recruit networks of regions.
Who showed it and when
Washington University in St. Louis led early PET mapping in the 1980s (Marcus Raichle, Michael Posner); Nancy Kanwisher's team in Cambridge, Massachusetts, described the 'fusiform face area' in 1997.
The evidence
Results repeat across labs and match lesion and stimulation evidence; large shared datasets like the Human Connectome Project allow independent checks.
Open questions
Activity is not proof a region causes a function; 'reverse inference', reading a mental state from which area lit up, is often unreliable.
▸Language and Chomsky's challenge to behaviorism was the first ability traced to Brain regions and localization of functionWell replicated
The connection
Language was the first mental ability convincingly pinned to a place. In 1861 Paul Broca found that a patient who understood speech but could only say 'tan' had damage in the left frontal lobe. In 1874 Carl Wernicke linked comprehension to the left temporal lobe. Localization of function was established.
Who showed it and when
Bicêtre Hospital, Paris, April 1861, patient Louis Victor Leborgne ('Tan'); Carl Wernicke in Breslau (now Wrocław, Poland), 1874.
The evidence
Broca's autopsy findings, Leborgne's brain preserved in Paris, and a 2007 MRI scan of it showing damage extended deeper than Broca described.
Open questions
Modern imaging shows language relies on wide left-hemisphere networks, not two spots; how this fits Chomsky's innate language faculty is debated.