Brain Structure and Function

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Brain Structure and Function
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• If the human brain were so simple that we could
  understand it, we would be so simple that we
  couldnt
• -Emerson Pugh, The Biological Origin of Human
  Values (1977)

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Phineas Gage

• September 13th, 1848
• Phineas 25 years old
• Rutland Burlington Railroad, Cavendish, VT
• Paving the way for new RR tracks
• Tamping Iron
• 1.25in x 3ft

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Phineas Gage

• Accident
• Quick Recovery
• Months later No longer Gage
• Before capable, efficient, best foreman,
  well-balanced mind
• After extravagant, anti-social, liar, grossly
  profane
• Stint with P.T Barnum
• Died 12 years later

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Evolution of the Brain

• Reptilian ? Paleomammalian ? Neomammalian

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The Brain

• Brainstem
• responsible for automatic survival functions
• Medulla
• controls heartbeat and breathing

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Parts of the Brain
THALAMUS ? Relays messages
amygdala
hippocampus
pituitary
CEREBELLUM ? Coordination and balance

• BRAINSTEM ? Heart rate and breathing

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Reticular Formation

• Widespread connections
• Arousal of the brain as a whole
• Reticular activating system (RAS)
• Maintains consciousness and alertness
• Functions in sleep and arousal from sleep

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The Cerebellum

• helps coordinate voluntary movement and balance

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The Limbic System

• Hypothalamus, pituitary, amygdala, and
  hippocampus all deal with basic drives, emotions,
  and memory
• Hippocampus ? Memory processing
• Amygdala ? Aggression (fight) and fear (flight)
• Hypothalamus ? Hunger, thirst, body temperature,
  pleasure regulates pituitary gland (hormones)

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The Limbic System

• Hypothalamus
• neural structure lying below (hypo) the thalamus
  directs several maintenance activities
• eating
• drinking
• body temperature
• helps govern the endocrine system via the
  pituitary gland
• linked to emotion

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The Limbic System

• Amygdala
• two almond-shaped neural clusters that are
  components of the limbic system and are linked to
  emotion and fear

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The Brain

• Thalamus
• the brains sensory switchboard, located on top
  of the brainstem
• it directs messages to the sensory receiving
  areas in the cortex and transmits replies to the
  cerebellum and medulla

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The Cerebral Cortex

• Cerebral Cortex
• the bodys ultimate control and information
  processing center

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The lobes of the cerebral hemispheres
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The lobes of the cerebral hemispheres
Planning, decision making speech
Sensory
Vision
Auditory
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The Cerebral Cortex

• Frontal Lobes
• involved in speaking and muscle movements and in
  making plans and judgments
• the executive
• Parietal Lobes
• include the sensory cortex

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The Cerebral Cortex

• Occipital Lobes
• include the visual areas, which receive visual
  information from the opposite visual field
• Temporal Lobes
• include the auditory areas, each of which
  receives auditory information primarily from the
  opposite ear

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The Cerebral Cortex

• Frontal (Forehead to top) ? Motor Cortex
• Parietal (Top to rear) ? Sensory Cortex
• Occipital (Back) ? Visual Cortex
• Temporal (Above ears) ? Auditory Cortex

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Motor/Sensory Cortex

• Contralateral
• Homunculus
• Unequal representation

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Sensory Areas Sensory Homunculus
Figure 13.10
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The Cerebral Cortex

• Aphasia
• impairment of language, usually caused by left
  hemisphere damage either to Brocas area
  (impairing speaking) or to Wernickes area
  (impairing understanding) see clips
• Brocas Area
• an area of the left frontal lobe that directs the
  muscle movements involved in speech
• Wernickes Area
• an area of the left temporal lobe involved in
  language comprehension and expression

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Language Areas

• Broca ? Expression
• Wernicke ? Comprehensionand reception
• Aphasias

LEFT HEMISPHERE
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Paul Broca 1800s

• Suggested localization

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Techniques to examine functions of the brain
1. Remove part of the brain see what effect it
has on behavior
2. Examine humans who have suffered brain damage
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3. Stimulate the brain
4. Record brain activity
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Brain Lateralization
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Our Divided Brains

• Corpus collosum large bundle of neural fibers
  (myelinated axons, or white matter) connecting
  the two hemispheres

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Hemispheric Specialization

• LEFT
• Symbolic thinking
• (Language)
• Detail
• Literal meaning

RIGHT Spatial perception Overall
picture Context, metaphor
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Contra-lateral division of labor

• Right hemisphere controls left side of body and
  visual field
• Left hemisphere controls right side of body and
  visual field

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Split Brain Patients

• Epileptic patients had corpus callosum cut to
  reduce seizures in the brain
• Lives largely unaffected, seizures reduced
• Affected abilities related to naming objects in
  the left visual field

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Brain Plasticity
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Brain Plasticity

• The ability of the brain to reorganize neural
  pathways based on new experiences
• Persistent functional changes in the brain
  represent new knowledge
• Age dependent component
• Brain injuries

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Environmental influences on neuroplasticity
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Sensation and Perception
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Sensation

• The process by which the central nervous system
  receives input from the environment via sensory
  neurons
• Bottom up processing

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Perception

• The process by which the brain interprets and
  organizes sensory information
• Top-down processing

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The psychophysics of sensation

• Absolute threshold ? the minimum stimulation
  needed to detect a stimulus with 50 accuracy
• Subliminal stimulation ? below the absolute
  threshold for conscious awareness
• May affect behavior without conscious awareness
• Sensory adaptation/habituation ? diminished
  sensitivity to an unchanging stimulus

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The five major senses

• Vision electromagnetic
• Occipital lobe
• Hearing mechanical
• Temporal lobe
• Touch mechanical
• Sensory cortex
• Taste chemical
• Gustatory insular cortex
• Smell chemical
• Olfactory bulb
• Orbitofrontal cortex
• Vomeronasal organ?

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The sixth sense
And the seventhand eighthand ninth

• Vestibular ? balance and motion
• Inner ear
• Proprioceptive ? relative position of body parts
• Parietal lobe
• Temperature ? heat
• Thermoreceptors throughout the body, sensory
  cortex
• Nociception ? pain
• Nociceptors throughout the body, sensory cortex

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Thresholds of the five major senses
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The Retina

• The retina at the back of the eye is actually
  part of the brain!

• Rods brightness
• Cones color