Topic 1.4 Notes – The Brain

What the Brain Does

The brain coordinates behavior and mental processes. That includes obvious actions like moving your hand and less visible things like memory, emotion, language, and judgment.

Two ideas have to stay together:

• Localization of function means some brain regions are especially linked to certain jobs.
  • Example: the occipital lobe is strongly tied to vision.
• Integration means most behavior uses networks, not one isolated spot.
  • Example: speaking involves language areas, motor control, hearing, and attention.

A common AP move is giving you a symptom and asking for the structure. Your job is to match the main loss or change to the brain area most associated with it.

This brain diagram is a good quick reference for the big regions you will keep seeing, especially the lobes, cerebellum, and brain stem.

Major brain regions

Major Brain Structures and What They Control

Brain stem, reticular formation, reward system, and cerebellum

• Brain stem handles basic survival functions.
• Medulla regulates breathing and heart rate.
• Reticular formation or reticular activating system helps with alertness, arousal, attention, eye movement, and some movement. Major damage can reduce consciousness.
• Reward center means a dopamine-linked network involved in reinforcement, motivation, some learning, cognition, and emotion. It is a network, not one tiny “pleasure spot.”
• Cerebellum helps balance, coordination, smooth voluntary movement, and some procedural learning like learned skills.

Limbic system

This group is big for emotion, memory, motivation, and body regulation.

• Thalamus relays most sensory information to the right cortical area. Smell is the main exception.
• Hypothalamus maintains homeostasis such as hunger, thirst, and body temperature. It also links the nervous and endocrine systems.
• Pituitary gland is the “master gland” that releases hormones under hypothalamic control.
• Hippocampus forms new explicit memories for facts and events.
• Amygdala is tied to fear, threat detection, aggression, and emotional significance.

Cerebral cortex and the four lobes

The cerebral cortex is the outer layer for complex processing and has two hemispheres.

• Occipital lobes process vision.
• Temporal lobes process hearing and language comprehension.
• Parietal lobes help integrate information and contain the somatosensory cortex, which maps body touch sensations. This map is contralateral, so the left hemisphere processes the right side of the body.
• Frontal lobes handle language, planning, judgment, higher-order thinking, and voluntary movement.
  • Prefrontal cortex supports executive functions like planning, decision-making, and impulse control.
  • Motor cortex controls skeletal movement and also works contralaterally.

The labeled cortical map below connects these lobe functions to specific areas you should recognize, especially the motor cortex, somatosensory cortex, visual cortex, auditory cortex, and the language areas Broca’s and Wernicke’s.

Hemispheres, Language, and Split-Brain Findings

The corpus callosum is the fiber bundle connecting the hemispheres. It lets the two sides share information.

Lateralization means some functions are more associated with one hemisphere:

• Left hemisphere is usually language dominant.
• Right hemisphere is often stronger in spatial and perceptual tasks.

Do not fall for the myth that people are simply “left-brained” or “right-brained.”

Language areas are usually on the left:

• Broca’s area in the left frontal lobe helps speech production.
• Wernicke’s area in the left temporal lobe helps language comprehension.
• Aphasia means language impairment from brain damage.
• Broca’s patient “Tan” helped show localization of speech production.

Split-brain research showed this step by step. In the illustration, focus on the idea that information shown to one visual field is processed by the opposite hemisphere.

1. The corpus callosum was severed to reduce severe epilepsy.
2. Sperry and Gazzaniga studied these patients.
3. Right visual field → left hemisphere so the person can usually name the object.
4. Left visual field → right hemisphere so a split-brain patient may not verbally name it.
5. The left hand can still point to it because the right hemisphere processed it.

Split-brain visual field testing

Damage, Plasticity, and Classic Case Studies

Neuroplasticity is the brain’s ability to rewire or change connections. It is strongest early in life but continues in adulthood. It can support recovery after damage, though recovery is often partial.

Classic cases:

• Phineas Gage had frontal lobe damage linked to personality, judgment, and impulse-control changes.
• Henry Molaison (H.M.) had hippocampal damage and could not form new explicit memories, though some procedural learning remained.

Fast matches you should know:

• breathing or heart rate → medulla
• alertness loss → reticular formation
• poor balance → cerebellum
• vision problems → occipital lobe
• comprehension problems → temporal lobe or Wernicke’s area
• touch problems → parietal lobe or somatosensory cortex
• movement problems on opposite side → motor cortex
• poor planning or impulse control → prefrontal cortex
• no new explicit memories → hippocampus
• abnormal fear or aggression → amygdala
• homeostasis problems → hypothalamus

How Psychologists Study the Brain

Different methods answer different questions.

The best conclusion uses converging evidence. If imaging, lesions, and case studies all point to the same function, the claim is much stronger.