The Brain

Studying the Brain

1) Case studies (injuries or disease)

2) Lesioning

3) Electrical stimulus

4) CT scan (CAT scan)

• X-rays
• Structural

5) MRI (Magnetic Resonance Imaging)

• Structural
• Higher resolution

6) Pet scan (Positron Emission Tomography)

• Functional
• Radioactive glucose/blood flow shows active areas

7) fMRI (Functional MRI)

• Functional
• Images in quick succession → gives information about blood flow

8) EEG (Electroencephalogram)

• Functional imaging
• Sleep studies
• Seizures

Brain Structure

I. Hindbrain

Brain stem = medulla + pons

• Medulla
  • Vital automatic functions
  • Heartbeat, breathing
• Pons (”bridge”)
  • Automatic functions
  • Transmits information from motor cortex to cerebellum
  • Facial expressions
  • Sleep/wake cycles
  • Swallowing
  • Blinking
  • Bladder control
• Cerebellum (”little brain”)
  • Muscle movement
  • Coordination
  • Balance
  • Implicit memory → procedural, learned responses (ex. riding a bike)

II. Midbrain

• Posture, walking
• Eye movements

Reticular Formation

• Extends through the medulla, pons, and midbrain then terminates in the thalamus
• Arousal
• Habituation

III. Forebrain

• Hypothalamus

  • Switchboard
  • Receives sensory information → sends to the right place in the cerebrum
  • All senses except smell

• Limbic System

  • Hypothalamus
  • Controls pituitary
  • Link between nervous and endocrine system
  • Homeostasis: body temperature, hunger, thirst
  • Reward center
  • Hippocampus
  • Involved in memory formation (declarative memories)
  • Amygdala
  • Strong emotions (ex. aggression, fear)

• Cerebral Cortex

  • Two hemispheres (left, right)
  • 8 lobes
  • Association area
  • Involved in complicated and nuanced behavior
  • Aphasia: language disorder
  • Broca’s Aphasia
    • Broca’s area: in frontal lobe
    • “Broken” speech: can understand but can’t communicate
  • Wernicke’s Aphasia
    • Wernicke’s area: in left temporal lobe
    • “Word salad”
    • No understanding of speech

  Lobes of the Cortex

  1. Occipital Lobe
  • Back of head
  • Visual cortex
    • Visual stimuli
    • Contralateral processing
      • Right side of brain controls and senses left visual field
      • Left side of brain controls and senses right visual field
  • Vision → sensory information → thalamus → occipital lobe
  1. Temporal Lobes
  • Above ears, on side of head
  • Involved in smell
    • Olfactory cortex
  • Involved in hearing
    • Auditory cortex
    • No contralateral processing
  • Wernicke’s area
    • Only on left side
    • Understanding language
  • Face recognition
  1. Frontal Lobe
  • Spontaneity
  • Personality
  • Memory
  • Problem solving
  • Abstract thought planning
  • Most association areas
  • Motor Cortex
    • “Headband” shape
    • The greater the amount of control needed, the greater the area devoted to it in the motor cortex
    • Contralateral processing
  • Broca’s area
    • Left side
    • Production of speech
  1. Parietal Lobes
  • Somatosensory cortex
  • The more sensitive the body part is, the more area of the cortex that is devoted to it
  • Brain plasticity
    • Body’s ability to change by building new pathways after damage or response experience
    • Existing neurons “take over” for damaged part
    • Especially in childhood
  • Neurogenesis
    • New neuron growth (not plasticity)

Lateralization

Lateralization: different sides of the brain specialize in different functions

Left Hemisphere

• Logic
• Rationality
• Analytical
• Language
• Right side of body

Right Hemisphere

• Recognition of emotion and faces
• Intuition
• Creativity
• Spacial/visual perception
• Left side of body

Corpus callosum

• Connects left and right hemispheres
• Split-brain patients: corpus callosum is severed, prevents hemispheres from communicating with each other

Information from left and right visual fields:

• Both eyes process information
• Left visual field → right side of brain
  • Patient can’t name stimulus but can draw with left hand
• Right visual field → left side of brain
  • Language and speech processed → can name object