Lecture: Structure of the Brain

Overview

• Focus on brain structures and their function relationships
• Organization: Telencephalon, Diencephalon, Mesencephalon, Metencephalon, Myelencephalon, Spinal Cord
• Evolution of the brain: Inside out (like building a rubber band ball)
• Primitive structures: Midbrain & Brainstem control survival functions (breathing, heart rate)
• Upper layers: Cortex for higher cognitive processes (emotion, memory)

Telencephalon

Cortex

• Forebrain region, including cortex and limbic system
• Cortex: Personality, decision-making, impulse control
  • Case study of Elliot: Tumor in frontal lobe -> rapid behavior change
  • Case study of Phineas Gage: Injury to prefrontal cortex -> change to impulsive behavior
• Six layers of the cortex (Layer 6 deepest)
• Layers 3 & 5: Large pyramidal neurons
• Regions: Primary sensory, secondary sensory, motor areas, and association areas

Limbic System

• Associated with emotion, memory
• Amygdala: Fear, learning fear, diagnosing fear in others
  • Urbach-Wiethe disease study: Difficulty diagnosing fear in others without a functioning amygdala
• Hippocampus: Long-term memory storage, episodic events, cognitive mapping
  • Study with taxi drivers: Larger hippocampus correlates with time spent navigating (neuroplasticity)

Diencephalon

Thalamus

• Central position, routing sensory info to cortex
• Internal capsule: Bundle of white matter sending info all over cortex
  • Corona Radiata: Distribution of these bundles

Hypothalamus

• Part of the limbic system
• Controls drives: Feeding, satiety, fight-or-flight response (HPA axis), sexual impulses
  • Lesion study in rats: Removing satiety signals leads to obesity
• Stress system, regulates need to drink

Mesencephalon (Midbrain)

Basal Ganglia and Dopamine Paths

• Dopamine paths: Mesocortical limbic circuitry, involved in reward, decision-making
• Structures: Globus pallidus, putamen, caudate, substantia nigra
• Subtantia nigra: Dopamine production, sending signals to basal ganglia and primary motor cortex
• Tectum (Superior & Inferior colliculi): Visual and auditory orienting responses
• Cerebral Aqueduct: Flow of CSF through midbrain to spinal cord
• VTA: Reward learning, addiction

Metencephalon and Myelencephalon (Hindbrain)

Cerebellum

• Coordinates balance, automatic sequences of movements (e.g., casting a fishing rod)
• Involved in basic associative conditioning (eye blink reflex)
• Layered, functions as a 'little brain'

Brain Stem

• Controls autonomic functions: Respiration, heart rate
• Arrangement: Midbrain -> Pons -> Medulla (MPM)
  • Pons: Respiratory centers, cranial nerve nuclei (for facial sensation, sleep, arousal)
  • Medulla: Cranial nerve nuclei (eye movement, facial muscles, swallowing)
• Reticular formation: Involved in sleep, wakefulness, arousal (spans midbrain, pons, medulla)