Brain Anatomy & Function (College Board AP® Psychology): Revision Note

The hindbrain

• The brain is the body's central processing center, responsible for regulating behavior, thought, emotion, and all bodily functions

• Understanding the functions of brain structures allows psychologists to explain how damage or disruption to specific regions affects behavior and mental processes

• The brain is divided into three broad regions that reflect its evolutionary development:

  • The hindbrain is the oldest region and controls basic survival functions

  • The midbrain controls alertness and connects the hindbrain to the forebrain

  • The forebrain is the most recently evolved region, controlling complex thought, emotion, and behavior

• The hindbrain is the most primitive part of the brain evolutionarily and is responsible for life-sustaining functions

  • It is composed of the brainstem (including the medulla), the cerebellum, and connects to the reticular activating system

The brainstem and medulla

• The brainstem connects the brain to the spinal cord and serves as a relay station for signals traveling between the brain and the rest of the body

• The medulla is located at the base of the brainstem and controls essential autonomic functions including:

  • breathing

  • heart rate

  • blood pressure

  • swallowing and digestion

• Because the medulla controls these basic life-sustaining processes, damage to it can be life-threatening

• The pons sits just above the medulla and acts as a bridge between the medulla and the rest of the brain. It plays a role in:

  • relaying sensory information to the brain

  • sleep and arousal

  • the control of REM sleep

The cerebellum

• The cerebellum ("little brain") is located at the rear base of the brain and generally controls:

  • coordination of muscle movement

  • balance and posture

  • some forms of procedural learning (i.e. the automatic performance of well-practiced skills)

    • e.g. riding a bike or playing a musical instrument

• The cerebellum does not initiate movement but fine-tunes and coordinates it

  • Without the cerebellum, movements become jerky and uncoordinated

• Damage to the cerebellum can result in loss of balance, impaired coordination, and difficulty with motor tasks

The midbrain

• The midbrain connects the hindbrain to the forebrain and plays a key role in alertness, arousal, and some aspects of movement

The reticular activating system (RAS)

• The reticular activating system is a network of neurons running through the midbrain and into the brainstem

• It generally controls:

  • alertness and wakefulness by:

    • filtering incoming sensory information

    • regulating transitions between sleep and waking

  • some voluntary movement

  • eye movement

  • some types of learning, cognition, and emotion

• The RAS acts as the brain's "gatekeeper," determining which incoming stimuli receive conscious attention and which are filtered out

• Damage to or disruption of the RAS can result in reduced consciousness, coma, or sleep disorders

The brain's reward center

• The brain's reward center operates via dopaminergic pathways and generally controls:

  • the anticipation and experience of reward and pleasure

  • motivation and goal-directed behavior

  • some types of learning through reinforcement

• The nucleus accumbens is a key structure within the reward center

  • It is heavily involved in pleasure, reward, and motivation

  • Many addictive drugs trigger dopamine release specifically here, creating intense feelings of reward that reinforce repeated drug use

• The reward center is heavily implicated in addiction

  • Many psychoactive drugs produce their pleasurable effects by stimulating dopamine release in this pathway, reinforcing repeated drug use

The forebrain

• The forebrain is the largest and most recently evolved part of the brain and it:

  • is responsible for the most complex aspects of human behavior, thought, and emotion

  • includes the limbic system and the cerebral cortex

The limbic system

• The limbic system is a set of interconnected structures located beneath the cerebral cortex that plays a central role in:

  • emotion

  • memory

  • motivation

• Key structures of the limbic system include:

The cerebral cortex

• The cerebral cortex is the outer layer of the brain

  • This is the deeply folded surface that gives the brain its wrinkled appearance

• It is divided into two hemispheres (left and right), which are connected by the corpus callosum

• The cerebral cortex is responsible for the most sophisticated human functions:

  • perception

  • language

  • higher-order thinking

  • decision-making

  • voluntary movement

The corpus callosum

• The corpus callosum is a thick band of nerve fibers that connects the left and right hemispheres, allowing them to communicate and share information

• When the corpus callosum is severed (a procedure sometimes performed to treat severe epilepsy)the two hemispheres can no longer communicate directly

  • Patients that have undergone this procedure are known as split-brain patients

Hemispheric specialization and split-brain research

• Research on split-brain patients has revealed that the left and right hemispheres may specialize in different functions

  • This is known as lateralization

• The left hemisphere is typically dominant for language processing, including:

  • Broca's area, which is responsible for speech production

    • Damage to this area causes Broca's aphasia, in which a person understands language but cannot produce fluent speech

  • Wernicke's area, which is responsible for speech comprehension

    • Damage to this area causes Wernicke's aphasia, in which a person produces fluent but meaningless speech

• The right hemisphere is typically dominant for spatial processing, facial recognition, and holistic perception

• Researchers test for hemispheric specialization in split-brain patients by presenting information to one visual field at a time

  • This takes advantage of the brain's contralateral organization

    • Contralateral organization refers to the principle that the left hemisphere processes information from the right visual field and vice versa

The four lobes of the cerebral cortex

• The cerebral cortex is further divided into four lobes, each with distinct functions:

Brain plasticity

• Brain plasticity, also called neuroplasticity, is the ability of the brain to rewire itself by modifying or creating new neural connections throughout development and in response to experience, injury, or disease

  • Plasticity allows the function of a damaged brain region to be assumed by a different region, enabling partial recovery from injury

  • E.g. a patient who suffers damage to Broca's area may partially recover speech production as other brain regions adapt and take over

• Plasticity is greatest in childhood but continues throughout the lifespan

  • Younger brains are generally more plastic and better able to compensate for damage