Limbic System & Cortex — Quick Reference

Location and role: sits between the brain's older structures and the cerebral hemispheres; associated with emotions and drives.
Key components: amygdala, hypothalamus, hippocampus.

Two almond-shaped clusters; central to fear and aggression.
Classic findings: Kläuver-Bucy and cases like S. M. ("the woman with no fear"); smaller amygdala linked to reduced arousal to threats.
Functions extend beyond fear: interacts with other brain regions; not the sole center for emotion.
Experimental evidence: electrical stimulation can provoke fear/attack in animals; damage reduces fear in monkeys/humans; responds to angry faces among others.

Location: just below the thalamus; important for bodily maintenance and homeostasis.
Roles: regulates hunger, thirst, body temperature, sexual behavior; influences the endocrine system via the pituitary gland.
Brain–endocrine interaction: brain activity can influence hormones, which in turn influence the brain.

Reward centers discovered in the hypothalamus; rats will self-stimulate; other centers include nucleus accumbens.
Dopamine-related system supports pleasure, motivation, and reward-driven behavior; linked to eating, drinking, sex.
Dopamine modulation of pleasure: increasing dopamine can enhance pleasurable chills; deficits can reduce pleasure.
Concept: reward systems may underlie both survival behaviors and maladaptive behaviors.

Shape and role: seahorse-shaped; processes conscious, explicit memories (facts and events) for storage.
Consequences of damage: impaired ability to form new memories; aging and injury can shrink hippocampus and impair memory.
Relevance to memory research and learning.

Structure: wrinkled outer layer; contains about 2.0\times 10^{10} neurons and 3.0\times 10^{14} synapses.
Four lobes: frontal, parietal, occipital, temporal.
Overall function: thinking, perceiving, language; highly interconnected networks across lobes.

Motor cortex (frontal lobe): controls voluntary movements; mapping shows that areas requiring precise control occupy more cortical space (homunculus).
Somatosensory cortex (parietal lobe): processes touch and body position; greater sensitivity areas have larger representations.
Brain–machine interfaces: research enables thought-driven control of external devices and assistive technologies.

Visual cortex (occipital lobe): processes visual input; damage can affect vision; LSD studies show increased cross-communication between regions.
Auditory cortex (temporal lobe): processes sound; input from the opposite ear; auditory hallucinations linked to temporal lobe activity.

Not primary sensory/motor regions; support higher mental functions (learning, remembering, thinking, speaking).
Prefrontal cortex: planning, judgment, social behavior, processing new memories; damage can impair planning and inhibitory control.
Parietal association areas: mathematical/spatial reasoning; Einstein’s brain example; stimulation can influence perception of movement.
Right temporal association area: face recognition; damage can impair recognizing familiar people despite describing features.
Takeaway: complex tasks rely on networks and functional connectivity across areas; avoid simplistic localization.

Frontal lobe damage linked to personality and behavior changes; Gage case showed loss of emotion regulation and moral judgment after injury.

Complex behaviors arise from distributed networks; functional connectivity matters as much as localized regions.

Two facts about damage: many neurons do not regenerate; some brain functions are preassigned to areas.
Neuroplasticity allows reorganization after damage, especially in children.
Constraint-induced therapy: restrain functional limb to rewire brain and improve dexterity after stroke or injury.
Hemispherectomy evidence: remaining hemisphere can take over many functions in young children; memory and personality often preserved to a surprising extent.

Advances show thought-to-movement control via motor cortex signals; prosthetic limbs and even a prosthetic voice are being developed.

Key Numbers (for quick recall)