Brain Structures Functions

Why This Matters

The brain is the biological foundation of everything you study in psychology—from how you form memories to why you feel fear, from how you control your movements to how you make decisions. On the AP Psychology exam, you're being tested on your ability to connect specific brain structures to their functions and, more importantly, to understand how damage or dysfunction in these areas produces observable changes in behavior and cognition. This means you need to know not just what the hippocampus does, but why damage to it would impair memory formation while leaving other functions intact.

Brain structures don't work in isolation—they form interconnected systems that handle sensation and perception, memory consolidation, emotional processing, motor control, and executive functions. The exam loves to test your understanding of these systems through case studies (think Phineas Gage or H.M.) and scenarios asking you to predict behavioral outcomes from brain damage. Don't just memorize a list of structures—know what concept each structure illustrates and how it connects to the broader themes of Unit 1 (Biological Bases of Behavior) and beyond.

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The Cerebral Cortex: Higher-Order Processing

The cerebral cortex is the brain's outer layer of gray matter where complex thinking happens. Each of its four lobes specializes in different types of processing, and understanding this division of labor is essential for predicting how localized damage affects behavior.

Cerebral Cortex

• Outermost layer of the brain—responsible for higher-level functions including thought, reasoning, language, and conscious experience
• Divided into four lobes (frontal, parietal, temporal, occipital), each handling specialized functions while working together through neural networks
• Processes sensory information and controls voluntary movement—damage to specific regions produces predictable deficits in corresponding functions

Frontal Lobe

• Executive functions headquarters—controls planning, problem-solving, impulse control, and working memory (connects directly to Topic 2.2 on thinking and decision-making)
• Contains the primary motor cortex—the precentral gyrus that controls voluntary muscle movements in a topographic map of the body
• Critical for personality and emotional regulation—Phineas Gage's case demonstrated how frontal lobe damage can dramatically alter behavior while leaving other functions intact

Parietal Lobe

• Processes somatosensory information—touch, temperature, pain, and proprioception through the postcentral gyrus (somatosensory cortex)
• Contains a sensory homunculus—a distorted body map where more sensitive areas (hands, lips) have larger cortical representation
• Essential for spatial awareness—damage can cause hemispatial neglect, where patients ignore one side of space entirely

Temporal Lobe

• Primary auditory processing center—interprets sounds and is essential for language comprehension (Wernicke's area is located here)
• Houses the hippocampus—making this lobe critical for memory formation and the transition from short-term to long-term memory
• Processes complex visual stimuli—including face recognition; damage can cause prosopagnosia (face blindness)

Occipital Lobe

• Primary visual processing center—contains the visual cortex that interprets information from the retina via the optic nerve
• Specialized regions for different visual features—separate areas process color, motion, shape, and spatial location
• Damage causes cortical blindness—patients cannot consciously see despite having functional eyes, demonstrating that vision requires brain processing

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The Prefrontal Cortex: Executive Control Center

The prefrontal cortex deserves special attention because it's central to what makes human cognition unique. This region doesn't fully mature until the mid-20s, which explains many adolescent behaviors the exam might ask about.

Prefrontal Cortex

• Controls complex cognitive behavior—decision-making, goal-directed behavior, and the executive functions tested in Topic 2.2 (inhibitory control, cognitive flexibility, working memory)
• Moderates personality and social behavior—the Phineas Gage case is the classic example of how prefrontal damage changes who a person seems to be
• Last brain region to fully develop—explains why adolescents show poorer impulse control and risk assessment compared to adults

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The Limbic System: Emotion and Memory

The limbic system is a network of structures that handle emotional processing, memory formation, and motivated behavior. These structures sit beneath the cortex and connect emotional significance to our experiences—explaining why emotionally charged events are remembered better.

Limbic System (Overview)

• Interconnected network for emotion and memory—includes the hippocampus, amygdala, hypothalamus, and other structures working together
• Links emotional significance to experiences—explains why you remember your first day of school but not your 47th
• Drives motivated behavior—hunger, thirst, sex, and other survival-related drives originate here

Hippocampus

• Critical for forming new explicit memories—patient H.M. could not form new declarative memories after hippocampal removal (directly connects to Topic 2.3 on memory)
• Handles memory consolidation—transfers information from short-term to long-term storage, particularly episodic and semantic memories
• Vulnerable to chronic stress—elevated cortisol can damage hippocampal neurons, linking stress to memory impairment

Amygdala

• Processes emotional significance—particularly fear, but also other emotions; assigns emotional weight to stimuli
• Triggers fight-or-flight response—activates the sympathetic nervous system through connections to the hypothalamus
• Strengthens emotional memories—explains why traumatic or highly emotional events are remembered vividly (flashbulb memories)

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Relay and Regulation Centers

These structures act as the brain's switchboard and thermostat—routing information to appropriate destinations and maintaining the body's internal balance. Understanding their roles helps explain how sensory information reaches consciousness and how the brain controls bodily functions.

Thalamus

• Sensory relay station—routes nearly all sensory information (except smell) to the appropriate cortical areas for processing
• Regulates consciousness and alertness—damage can cause coma or persistent vegetative states
• Filters incoming information—determines what sensory data reaches conscious awareness, playing a role in selective attention

Hypothalamus

• Master regulator of homeostasis—controls body temperature, hunger, thirst, and circadian rhythms (the "four F's": fighting, fleeing, feeding, mating)
• Controls the endocrine system—directs the pituitary gland, making it the link between nervous and endocrine systems
• Mediates stress response—activates the HPA axis (hypothalamic-pituitary-adrenal) during stress, relevant to Unit 5 topics

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Movement and Coordination

Motor control involves multiple brain regions working together. The cortex plans movements, the basal ganglia initiate and regulate them, and the cerebellum fine-tunes them. This distributed system explains why different types of movement disorders affect different aspects of motor control.

Cerebellum

• Coordinates voluntary movement and balance—damage causes ataxia (uncoordinated, jerky movements) rather than paralysis
• Essential for motor learning—procedural memories like riding a bike depend on cerebellar function (connects to implicit memory in Topic 2.3)
• Involved in cognitive functions—recent research shows roles in attention, language, and timing, though motor coordination remains its primary function

Basal Ganglia

• Regulates voluntary motor control—initiates and smooths movements; dysfunction causes Parkinson's (too little movement) or Huntington's (too much movement)
• Critical for habit formation—procedural learning and automatic behaviors depend on basal ganglia circuits
• Works with prefrontal cortex—forms loops that connect motivation to action, explaining why reward affects movement initiation

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Integration and Communication

Brainstem

• Controls basic life functions—breathing, heart rate, blood pressure, and other autonomic processes that continue even during sleep or coma
• Contains three regions—midbrain (reflexes, eye movement), pons (sleep, arousal), and medulla oblongata (vital functions)
• Relay center for neural signals—all information traveling between brain and body passes through the brainstem

Corpus Callosum

• Connects the two hemispheres—this thick band of 200+ million nerve fibers allows the left and right brain to communicate
• Enables integrated functioning—split-brain patients (with severed corpus callosum) show fascinating deficits in cross-hemisphere communication
• Allows information transfer—visual information from one side can be verbally reported because it crosses to the language-dominant hemisphere

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Quick Reference Table

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Self-Check Questions

1. Compare and contrast the roles of the hippocampus and amygdala in memory. How would damage to each structure differently affect a person's ability to remember a traumatic event?

2. A patient can see objects clearly but cannot recognize familiar faces. Which brain structure is most likely damaged, and which lobe contains it?

3. Which two structures are both involved in motor control but would produce different symptoms if damaged? Describe how their functions differ.

4. If an FRQ asks you to explain why a teenager makes riskier decisions than an adult, which brain structure and what developmental fact should you reference?

5. A patient has damage to their thalamus. Which sensory system would still function relatively normally, and why? How would damage to the hypothalamus produce different symptoms?