Unit 1.4: The Brain

The Brain's Hierarchical Structure

The brain can be organized from bottom to top based on evolutionary development and functional complexity[web:55][web:59].

Medulla Oblongata

The medulla sits at the base of the brainstem and regulates vital automatic functions like breathing, heart rate, and blood pressure[web:55][web:59].

Key Functions:

• Controls heartbeat and heart rate
• Regulates breathing rate and respiration
• Manages blood pressure
• Coordinates reflexes like swallowing, sneezing, coughing, and vomiting

Critical Note: Damage to the medulla is often fatal because it controls life-sustaining functions that cannot be voluntarily controlled[web:55].

Pons

The pons (meaning "bridge") sits above the medulla and serves as a relay station connecting different parts of the brain[web:55][web:59].

Key Functions:

• Helps coordinate movement and posture
• Plays a role in sleep regulation and dreaming
• Involved in facial expressions
• Assists with sensory relay between the spinal cord and higher brain regions

Midbrain

The midbrain is involved in integrating sensory information and coordinating movement and reflexes[web:55].

The midbrain helps control eye movements, visual processing, and auditory reflexes (like turning toward a sudden sound)[web:55].

The Reticular Activating System (RAS) is a network of neurons running through the brainstem that controls arousal, alertness, and attention[web:55][web:59].

Key Functions:

• Regulates wakefulness and sleep — determines when you're alert or drowsy
• Filters incoming sensory stimuli — decides what information deserves attention
• Controls attention and focus — helps you concentrate on important tasks
• Influences motivation — affects drive and goal-directed behavior

Example: The RAS is what keeps you awake during class or allows you to sleep through background noise. Damage to the RAS can result in coma or impaired consciousness[web:55][web:59].

The cerebellum ("little brain") is located at the back of the brain, beneath the cerebral cortex, and specializes in coordinating movement and balance[web:55][web:59].

Key Functions:

• Coordinates muscle activity for smooth, precise movements
• Maintains balance and posture
• Motor learning — helps you learn physical skills like riding a bike, typing, or playing sports
• Procedural memory — stores "muscle memory" for automatic actions
• May also play a role in attention and language

Example: Without a functioning cerebellum, simple tasks like walking in a straight line, catching a ball, or maintaining balance would be extremely difficult[web:55][web:59].

Thalamus: Sensory Relay Station

The thalamus acts as the brain's central relay station, directing all sensory information (except smell) to the appropriate areas of the cortex for processing[web:55].

Key Functions:

• Routes sensory signals (vision, hearing, touch, taste) to the cortex
• Helps regulate attention and consciousness
• Plays a role in sensory integration and filtering
• Minor involvement in memory and emotion

Think: The thalamus is like a switchboard operator routing calls to the right departments[web:55].

Hypothalamus: Body's Thermostat

The hypothalamus is a small but mighty structure that maintains homeostasis by regulating body temperature, hunger, thirst, and other vital drives[web:55][web:59].

Key Functions:

• Regulates body temperature (internal thermostat)
• Controls hunger and thirst drives
• Manages circadian rhythms (sleep-wake cycles)
• Regulates sexual behavior and reproduction
• Works with the endocrine system to control hormone release via the pituitary gland

Hippocampus: Memory Maker

The hippocampus is essential for forming and storing new explicit (declarative) memories — facts and events[web:55][web:59].

Key Functions:

• Converts short-term memories into long-term storage
• Critical for learning new information
• Important for spatial navigation and memory
• Forms episodic memories (personal experiences)

Clinical Example: Damage to the hippocampus can result in anterograde amnesia — the inability to form new long-term memories (like patient H.M.)[web:55].

Amygdala: Emotion Regulator

The amygdala processes strong emotions, especially fear, aggression, and anxiety[web:55][web:59].

Key Functions:

• Detects threats and triggers fight-or-flight response
• Involved in emotional learning (associating emotions with experiences)
• Forms emotional memories (especially fear-related)
• Processes aggression and anxiety

Clinical Note: Overactivity in the amygdala is linked to anxiety disorders, PTSD, and phobias[web:55].

Pituitary Gland: Master Gland

The pituitary gland, often called the "master gland," controls other glands in the endocrine system and regulates hormone production[web:55].

It works under the direction of the hypothalamus to regulate growth, reproduction, metabolism, stress response, and lactation[web:55].

The pituitary releases hormones like oxytocin (bonding, trust), growth hormone, and hormones that control other glands[web:55].

💡 Limbic System Memory Aid: "THiP HAM"

• T = Thalamus (sensory relay)
• Hi = Hypothalamus (homeostasis)
• P = Pituitary (hormone master)
• H = Hippocampus (memory)
• A = Amygdala (emotion)
• M = Memory tip — "The Hungry Pig Hides Almonds"

The cerebral cortex is the brain's outermost layer — the wrinkled "gray matter" responsible for higher-order thinking, perception, language, and voluntary behavior[web:55][web:59].

The cortex is divided into two hemispheres (left and right) connected by the corpus callosum. Each hemisphere contains four lobes[web:55][web:59].

Important: Each hemisphere controls the opposite (contralateral) side of the body — the left hemisphere controls the right side, and vice versa[web:55].

Hemispheric Specialization

Corpus Callosum: The Brain's Bridge

The corpus callosum is a thick bundle of neural fibers (white matter) that connects the left and right cerebral hemispheres, allowing them to communicate and share information[web:55][web:60].

Function: Transfers sensory, motor, and cognitive information between hemispheres so they can work together seamlessly[web:60].

1. Frontal Lobe: Executive Control Center

The frontal lobe is located at the front of the brain (behind the forehead) and is responsible for higher-order thinking, decision-making, and voluntary movement[web:55][web:59][web:62].

Key Functions:

• Planning and problem-solving
• Decision-making and reasoning
• Impulse control and emotional regulation
• Personality and social behavior
• Working memory and executive functions

Famous Case: Phineas Gage — survived a rod through his frontal lobe, resulting in dramatic personality changes and impaired impulse control[web:55].

2. Parietal Lobe: Sensory Integration

The parietal lobe is located at the top and back of the brain (crown area) and processes touch, body awareness, and spatial information[web:55][web:59][web:62].

Key Functions:

• Processes sensory information (touch, pressure, temperature, pain)
• Spatial awareness and navigation
• Body position (proprioception)
• Association areas that integrate and organize information

3. Temporal Lobe: Hearing and Memory

The temporal lobe is located on the sides of the brain (near the temples/ears) and specializes in auditory processing, language comprehension, and memory[web:55][web:59][web:62].

Key Functions:

• Processes auditory information (hearing and sound recognition)
• Language comprehension
• Memory formation (contains the hippocampus)
• Face recognition
• Object recognition

4. Occipital Lobe: Visual Processing

The occipital lobe is located at the very back of the brain and is exclusively dedicated to processing visual information[web:55][web:59][web:62].

Key Functions:

• Processes visual stimuli from the eyes
• Recognizes colors, shapes, and motion
• Interprets visual patterns
• Visual perception and awareness

💡 Four Lobes Memory Aid: "F.P.T.O."

"Frank's Pretty Terrific Optics" — or map them on your head:

• Forehead = Frontal lobe (planning, movement, speech production)
• Crown/Top = Parietal lobe (touch, body awareness)
• Temples/Ears = Temporal lobe (hearing, language comprehension, memory)
• Back = Occipital lobe (vision)

Lobes Quick Reference

💡 Broca vs. Wernicke Memory Trick

Think of a classroom scenario:

• Broca's area = Teacher speaking (producing language) — "Broca sounds like 'boca' (mouth in Spanish)"[web:55]
• Wernicke's area = Students listening and understanding what the teacher says (comprehending language)[web:55]

What is Split-Brain Surgery?

Split-brain surgery (corpus callosotomy) involves severing the corpus callosum to treat severe, medication-resistant epilepsy by preventing seizures from spreading between hemispheres[web:55][web:60][web:63].

After this surgery, the two hemispheres can no longer communicate directly, allowing researchers to study each hemisphere's specialized functions independently[web:60][web:63].

Key Findings from Split-Brain Research

Pioneering work by Roger Sperry and Michael Gazzaniga in the 1960s revealed hemispheric specialization through split-brain experiments[web:55][web:60][web:63].

How the Experiments Work:

1. Researchers present visual information to only one visual field at a time
2. Right visual field information → processed by left hemisphere (language center)
3. Left visual field information → processed by right hemisphere (non-verbal)
4. With the corpus callosum severed, information cannot transfer between hemispheres

Major Discoveries:

• Object shown to right visual field (left brain) → patient can name it verbally because the left hemisphere has language[web:60][web:63]
• Object shown to left visual field (right brain) → patient cannot name it but can select it with the left hand[web:60][web:63]
• Emotional reactions to images shown to the right hemisphere occur without verbal awareness[web:63]
• The left hemisphere often invents explanations (confabulation) for actions initiated by the right hemisphere[web:55]

Hemispheric Specialization Summary

⚠️ Important Note

There is no evidence for "right-brained" or "left-brained" personalities. People use both hemispheres for various tasks, and the brain works as an integrated whole[web:63].

What is Neuroplasticity?

Brain plasticity (neuroplasticity) refers to the brain's remarkable ability to reorganize itself, form new neural connections, and adapt in response to learning, experience, or injury[web:55][web:59][web:69][web:71].

The brain can modify existing connections, strengthen or weaken synapses, and even allow undamaged areas to take over functions of damaged regions[web:55][web:71].

Key Features of Neuroplasticity

• Strongest during childhood — young brains are highly adaptable and form connections rapidly[web:55]
• Continues in adulthood — adults can still learn and adapt, though more slowly[web:55][web:71]
• Enhanced by learning — new experiences strengthen neural pathways[web:71]
• Critical for recovery — enables rehabilitation after brain injury or stroke[web:59]
• Involves synaptic pruning — eliminates unused connections to increase efficiency[web:55]

Example: Stroke Recovery

Step-by-Step Process:

1. After a stroke, damaged neurons in the affected area may no longer function
2. Nearby healthy neurons detect missing signals
3. Through therapy and practice, these neurons form new connections
4. Undamaged areas gradually assume functions of the injured region
5. Over time, the individual may regain mobility or speech, demonstrating brain adaptability[web:59]

This capacity explains why intensive rehabilitation and consistency are key to recovery after brain injury[web:59].

Limitations of Plasticity

While the brain is adaptable, plasticity has limits. Some functions (especially those controlled by the brainstem like breathing) are difficult to reassign, and recovery depends on age, severity of damage, and timing of intervention[web:55].

⚠️ Exam Note

Know the strengths and limitations of each method. EEG has great temporal resolution but poor spatial resolution; fMRI has great spatial resolution but poor temporal resolution; all methods are correlational (they show associations, not causation)[web:55][web:59].

Multiple Choice Tips

• Know brain structure locations and functions — medulla, pons, cerebellum, RAS, limbic system structures, four lobes[web:55]
• Understand lateralization — left hemisphere = language, right hemisphere = spatial tasks[web:55]
• Master Broca's vs. Wernicke's — production vs. comprehension[web:55][web:62]
• Recognize split-brain experimental results — what happens when information is shown to each visual field[web:60][web:63]
• Know neuroplasticity — brain's ability to adapt and reorganize[web:55][web:71]
• Distinguish research methods — EEG vs. fMRI vs. PET scans[web:55][web:59]

Free Response Question (FRQ) Tips

• Use precise terminology: corpus callosum, lateralization, contralateral organization, neuroplasticity[web:55]
• Link structures to behaviors: hippocampus → memory formation, amygdala → fear response, frontal lobe → planning[web:55]
• Explain split-brain findings clearly: describe visual field experiments and hemisphere specialization[web:60][web:63]
• Apply research methods: explain which method would best answer a specific research question[web:55][web:59]
• Use case study examples: Phineas Gage (frontal lobe damage), H.M. (hippocampus damage), split-brain patients[web:55]

🔑 The Big Picture

The brain is organized hierarchically from brainstem (survival functions) to limbic system (emotion/memory) to cerebral cortex (higher thinking). The cortex has four lobes with specialized functions, two hemispheres with different strengths, and language areas (Broca's for production, Wernicke's for comprehension). Split-brain research reveals hemispheric specialization, and neuroplasticity allows the brain to adapt throughout life[web:55][web:59][web:60].

💡 Essential Concepts

• Medulla = vital functions
• Pons = sleep/coordination
• Cerebellum = balance/motor learning
• RAS = arousal/attention
• Thalamus = sensory relay
• Hypothalamus = homeostasis
• Hippocampus = memory formation
• Amygdala = emotion (fear)
• Frontal lobe = planning/motor
• Parietal lobe = touch/spatial
• Temporal lobe = hearing/memory
• Occipital lobe = vision
• Broca's = speech production
• Wernicke's = comprehension
• Corpus callosum = connects hemispheres
• Left brain = language/logic
• Right brain = spatial/creative
• Neuroplasticity = brain adaptation
• Split-brain = hemisphere studies