The brain controls how you move, think, learn, remember, feel, and respond to the world around you. It also manages essential functions that happen without conscious effort, including breathing, heart rate, sleep, and digestion. Although the brain works as an integrated system, its different regions have specialized roles that help explain how the body and mind function.
The brain has three major anatomical divisions: the cerebrum, the cerebellum, and the brainstem. Within these divisions are structures that contribute to language, memory, emotion, sensory processing, movement, attention, and many other abilities.
Understanding what each part does requires more than memorizing a list of functions. Most everyday activities, from recognizing a familiar face to riding a bicycle, depend on several brain regions communicating with one another. No single area works entirely alone.
The three major parts of the brain
The brain’s three major divisions have distinct responsibilities, although their functions overlap.
The cerebrum is the largest part of the brain. It supports conscious thought, perception, language, voluntary movement, planning, and memory. Its outer layer, called the cerebral cortex, contains much of the neural machinery involved in complex mental activity.
The cerebellum sits at the back of the brain, beneath the cerebrum. It helps coordinate movement, maintain balance and posture, and refine motor skills. It also contributes to certain cognitive processes, including attention and aspects of learning.
The brainstem connects the brain with the spinal cord. It regulates essential functions such as breathing, heart rate, blood pressure, swallowing, and wakefulness. It also carries signals between the brain and the rest of the body.
These divisions are connected by extensive networks of nerve cells. Their cooperation allows a person to perform complicated tasks while maintaining the basic functions necessary for life.
What does the cerebrum do?
The cerebrum consists of two large halves, called the left and right cerebral hemispheres. Its folded outer surface increases the amount of cerebral cortex that fits inside the skull.
The cortex processes sensory information, supports voluntary movement, and contributes to reasoning, language, decision-making, and conscious experience. Beneath it lie structures involved in emotion, memory, motivation, and movement control, along with large bundles of nerve fibers that connect different brain regions.
Each hemisphere has four commonly recognized lobes: the frontal, parietal, temporal, and occipital lobes. These lobes are useful landmarks, but their boundaries do not represent completely separate functional systems.
The frontal lobe: Thinking, planning, and movement
The frontal lobe lies behind the forehead. It plays a major role in planning, problem-solving, decision-making, attention, emotional regulation, and voluntary movement.
Its functions include several distinct processes. The prefrontal cortex, located toward the front of the frontal lobe, helps people maintain goals, weigh alternatives, control impulses, and adjust their behavior to changing circumstances. These abilities are often grouped under the term executive functions.
Other parts of the frontal lobe help produce speech and control voluntary movements. The primary motor cortex, located near the back of the frontal lobe, sends signals that contribute to movements of the body’s muscles. Nearby regions help select, organize, and prepare movements before they occur.
A region in the dominant hemisphere, usually the left, is involved in producing spoken language. Known as Broca’s area, it contributes to the planning and organization of speech. Speaking fluently, however, also requires coordination with other language and motor networks.
Damage to the frontal lobe can affect judgment, attention, personality-related behavior, speech production, or movement, depending on the location and extent of the injury. A person may retain general intelligence while struggling to organize tasks or control impulses.
The parietal lobe: Touch and spatial awareness
The parietal lobe sits behind the frontal lobe and above the temporal lobe. It processes and integrates information about touch, pressure, temperature, pain, and the position of body parts.
The primary somatosensory cortex, located near the front of the parietal lobe, receives much of the sensory information that allows you to recognize where and how your body is being touched. Other parietal regions combine these signals with visual and other sensory information.
This integration helps you reach for a cup without constantly looking at your hand, navigate a crowded room, and understand how your body is positioned in space. The parietal lobe also contributes to attention, numerical processing, reading, and certain aspects of spatial reasoning.
Injury to particular parietal regions can interfere with recognizing objects by touch, directing attention to one side of space, or accurately perceiving the body’s position. The effects depend on which hemisphere and specific networks are affected.
The temporal lobe: Hearing, language, and memory
The temporal lobes lie on the sides of the brain, roughly behind the temples. They help process sound, understand language, recognize objects and faces, and form or retrieve memories.
The auditory cortex, located in the temporal lobe, processes information carried from the ears. Additional temporal regions help distinguish speech sounds, interpret spoken language, and recognize meaningful patterns in sound.
Language comprehension often relies on networks in the dominant temporal hemisphere working with frontal and other cortical regions. The temporal lobes also contain structures important for memory, including the hippocampus and nearby areas.
The hippocampus is especially important for forming new memories of events and experiences. It helps organize information so that it can be retained and later retrieved. It does not serve as a permanent storage location for every memory; long-term memories depend on broader networks distributed across the brain.
Damage to different parts of the temporal lobe can affect language comprehension, memory formation, sound recognition, or the ability to recognize familiar people and objects.
The occipital lobe: Visual processing
The occipital lobe occupies the back of the brain and is primarily involved in vision.
The primary visual cortex receives organized visual information from pathways originating in the eyes. Other visual regions analyze features such as edges, orientation, color, motion, and shape. These signals are then processed through networks that help the brain identify objects, interpret scenes, and guide behavior.
Seeing is not simply a matter of receiving an image. The brain must interpret patterns of light and combine them with attention, memory, and expectations to make sense of what is in front of you.
Damage to visual processing regions can produce specific visual difficulties even when the eyes themselves function normally. Depending on the affected area, someone may lose part of the visual field or have trouble recognizing or interpreting what they see.
What do the left and right sides of the brain do?
The left and right cerebral hemispheres have many functions in common, but they also show important differences in specialization. This is called lateralization.
For most people, the left hemisphere plays a leading role in many language functions, including aspects of speaking, reading, and understanding words. The left hemisphere also contributes to certain forms of analytical and sequential processing.
The right hemisphere is particularly important for some aspects of spatial attention, visual-spatial processing, and interpreting patterns of prosody, the rhythm and intonation that convey meaning in speech. Both hemispheres contribute to complex reasoning, creativity, memory, and problem-solving.
The hemispheres communicate through a large bundle of nerve fibers called the corpus callosum. This connection allows information processed on one side to be shared with the other.
A common misconception is that people are either left-brained and logical or right-brained and creative. Scientific understanding does not support this simple division. Although certain functions are more strongly associated with one hemisphere, most complex activities require coordinated processing across both sides.
What does the cerebellum do?
The cerebellum, whose name means “little brain,” lies beneath the back of the cerebrum. It contains a dense concentration of neurons and is essential for making movements smooth, accurate, and coordinated.
The cerebellum receives information about intended movements, ongoing muscle activity, body position, and sensory feedback. It uses this information to help adjust the timing, force, and precision of movement.
When you walk, reach for an object, type, or play a musical instrument, the cerebellum helps coordinate the many small adjustments needed to perform the action reliably. It also contributes to balance, posture, and motor learning, allowing practiced movements to become more accurate with experience.
The cerebellum does not initiate every movement or directly control all muscles. Instead, it works with the motor cortex, brainstem, spinal cord, and other structures to refine movement and reduce errors.
The cerebellum also contributes to cognitive functions, including aspects of attention, language, and the regulation of thought. Its role is not limited to physical coordination.
Damage to the cerebellum can cause ataxia, a condition characterized by impaired coordination. Affected individuals may walk unsteadily, struggle with precise hand movements, have difficulty maintaining balance, or speak with irregular timing. These problems can occur even when muscle strength is relatively preserved.
What does the brainstem do?
The brainstem sits at the base of the brain, in front of the cerebellum, and connects the brain to the spinal cord. It consists of three main parts: the midbrain, pons, and medulla oblongata.
The brainstem is essential for survival because it contains circuits that regulate basic physiological functions. It also relays sensory and motor information and helps maintain alertness.
The midbrain: Movement, attention, and visual and auditory responses
The midbrain is the uppermost portion of the brainstem. It contributes to eye movements, motor control, alertness, and responses to visual and auditory information.
Some midbrain structures help direct the eyes and head toward sudden sounds or visual events. Other regions participate in movement regulation through connections with broader motor circuits. The substantia nigra, a structure involved in these circuits, contains neurons that produce dopamine, a chemical messenger important for movement and other functions.
Degeneration of dopamine-producing neurons in the substantia nigra is a key feature of Parkinson’s disease, which can cause slowness of movement, stiffness, and resting tremor.
The pons: Sleep, breathing, and communication
The pons lies between the midbrain and medulla. It contains pathways that connect different brain regions, including the cerebrum and cerebellum, and participates in regulating sleep, breathing, and facial movements and sensation.
The pons also helps coordinate eye movements and contributes to the control of chewing, facial expressions, and other functions through its connections with cranial nerves.
Because it serves as an important communication hub, damage to the pons can affect multiple functions at once, potentially including movement, sensation, breathing, and consciousness.
The medulla oblongata: Essential automatic functions
The medulla oblongata is the lowest part of the brainstem, where it connects with the spinal cord.
It contains neural circuits that help regulate heart rate, blood pressure, breathing, swallowing, coughing, and vomiting. These functions are largely automatic, meaning they do not require continuous conscious control.
The medulla also carries important nerve pathways between the brain and spinal cord. Many motor pathways cross to the opposite side in the lower brainstem, helping explain why one cerebral hemisphere generally controls movement on the opposite side of the body.
Severe damage to the medulla can be life-threatening because of its role in maintaining essential bodily functions.
What do the thalamus and hypothalamus do?
The thalamus and hypothalamus are two important structures located deep within the brain, beneath much of the cerebral cortex. Despite their similar names and close proximity, they have different primary roles.
The thalamus: Routing sensory information
The thalamus acts as a major relay and processing center for information traveling to the cerebral cortex. Most sensory information, including touch, sound, and visual signals, passes through thalamic pathways before reaching the relevant cortical areas. The main exception is olfactory information, which has a different initial route.
The thalamus does more than pass signals along. It helps regulate which information receives attention and contributes to the coordination of sensory processing, movement, and states of consciousness.
It also participates in circuits involved in sleep and wakefulness. Its connections with the cortex help shape how sensory information is processed and brought into conscious awareness.
The hypothalamus: Keeping the body in balance
The hypothalamus is a small but influential structure located below the thalamus. It helps maintain homeostasis, the body’s ability to keep internal conditions within workable ranges.
The hypothalamus monitors and regulates processes related to body temperature, hunger, thirst, sleep-wake rhythms, stress responses, and reproductive functions. It links the nervous system with the endocrine system, which uses hormones to coordinate activities throughout the body.
One of its most important connections is with the pituitary gland, a hormone-releasing gland beneath the brain. Through neural signals and hormones, the hypothalamus helps control processes such as growth, metabolism, reproduction, and the body’s response to stress.
For example, when the body becomes dehydrated, hypothalamic systems help generate thirst and promote the release of a hormone that reduces water loss through the kidneys. This illustrates how the brain can influence behavior and internal physiology at the same time.
What do the hippocampus and amygdala do?
The hippocampus and amygdala are structures in the medial temporal lobe, a region along the inner side of each temporal lobe. They are often discussed together because they contribute to memory and emotion, but their functions are distinct.
The hippocampus: Forming new memories
The hippocampus is central to forming new memories of facts and events, especially memories that can later be consciously recalled. It helps bind together different aspects of an experience, including where something happened, what occurred, and the context in which it took place.
It also contributes to spatial memory and navigation. By combining information about landmarks, locations, and relationships between places, hippocampal networks help people learn routes and remember environments.
The hippocampus is not the sole repository of long-term memory. As memories become established, their representation involves distributed networks across the cerebral cortex. The hippocampus remains important for many forms of relational and episodic memory, although its contribution varies with the type of memory and how it is used.
Damage to both hippocampi can severely impair the ability to form new lasting memories, even if older memories and other intellectual abilities remain partly intact.
The amygdala: Emotional significance and learning
The amygdala is a group of nuclei, or clusters of nerve cells, that helps the brain evaluate the emotional significance of experiences. It is especially well known for its role in learning about potential threats, but it also contributes to processing other emotionally important information.
The amygdala helps connect experiences with emotional responses and can influence attention, memory, and bodily reactions. For example, learning that a particular sound signals danger can involve the amygdala and its connections with sensory, memory, and autonomic systems.
The amygdala does not operate as a simple fear center. Emotional responses emerge from interactions among many regions, including the prefrontal cortex, hippocampus, hypothalamus, and brainstem. The amygdala helps evaluate relevant cues and coordinate appropriate responses within these broader networks.
What do the basal ganglia do?
The basal ganglia are a collection of structures deep within the cerebral hemispheres. They help regulate movement, action selection, habits, and aspects of motivation and learning.
Rather than directly issuing commands to individual muscles, the basal ganglia participate in circuits that help determine which actions are initiated, adjusted, or suppressed. They work closely with the cerebral cortex and thalamus to make movement more controlled and purposeful.
These structures also contribute to learning through reinforcement, in which the brain adjusts behavior based on outcomes. Repeated actions can become habits partly through changes in circuits involving the basal ganglia.
Parkinson’s disease illustrates the importance of these circuits. When dopamine signaling is disrupted by the loss of certain neurons in the substantia nigra, basal ganglia networks have difficulty regulating movement, contributing to symptoms such as slowness and stiffness.
What does the corpus callosum do?
The corpus callosum is a broad band of nerve fibers connecting the left and right cerebral hemispheres. It allows information to travel between the two sides so that their specialized processes can contribute to a unified response.
For example, information about an object may be processed by different networks in each hemisphere. Connections through the corpus callosum help combine that information, supporting coordinated perception, movement, and cognition.
The corpus callosum is not a brain lobe or a center for a particular mental ability. It is a communication pathway that enables distant regions to work together.
How do the parts of the brain work together?
The brain’s anatomy is often presented as a series of separate structures, but real-world activities depend on networks that cross those boundaries.
Consider catching a ball. Visual regions in the occipital and temporal lobes help process the ball’s appearance and movement. Parietal regions contribute to estimating its location in space. Frontal motor areas help plan and execute the reach, while the basal ganglia contribute to selecting and regulating the action. The cerebellum helps refine timing and accuracy, and sensory feedback allows the nervous system to adjust the movement as it unfolds.
Emotions and memory also emerge from coordinated activity. Recognizing a familiar person, for example, may involve visual recognition networks, memory systems, emotional processing, and language regions that help retrieve the person’s name.
Communication between these areas occurs through networks of neurons. Neurons transmit signals through electrical changes and chemical messengers, while connections between them can strengthen or weaken with experience. This capacity for the nervous system to change in response to learning or experience is called neuroplasticity.
Brain functions are therefore specialized but not completely isolated. A particular region may be especially important for one process while contributing to several others through its connections.
What happens when a part of the brain is damaged?
The effects of brain injury depend on which structures are affected, how extensive the damage is, and whether connected networks are disrupted. The same general location can produce different symptoms in different people because brain organization varies and many functions depend on overlapping systems.
Damage to the frontal lobe may interfere with planning, impulse control, speech production, or voluntary movement. Injury to the parietal lobe may affect sensation or spatial awareness. Temporal lobe damage can impair memory or language comprehension, while occipital damage can disrupt visual processing. Cerebellar injury often causes poor coordination, and brainstem damage can affect breathing, swallowing, movement, or consciousness.
The brain also has some capacity to reorganize after injury. Rehabilitation can help people regain skills or develop alternative ways to perform tasks, although recovery depends on the nature and severity of the damage, the person’s overall health, and other factors. Neuroplasticity does not mean that every injury can be fully reversed.
Sudden neurological symptoms—including facial drooping, weakness or numbness on one side, difficulty speaking, abrupt vision changes, or a sudden loss of balance—can indicate a stroke. These symptoms require emergency medical attention, even if they improve quickly.
Understanding the brain’s major regions provides a useful map of how human abilities are organized. The most important distinction is that these structures have specialized roles, but perception, thought, emotion, movement, and bodily regulation arise from their continuous cooperation.
