THE BIOLOGICAL PERSPECTIVE

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THE BIOLOGICALPERSPECTIVE

• METHODOLOGIES

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Biological Perspective

• Linking the introspective study of consciousness
  (what you are thinking and feeling based on
  mental self-report)
• With what is happening at the biological level
  (brain activity at different sites and changes in
  chemical messengers)

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Methodologies

• Correlational Studies
• Experiments
• Observations
• Case Studies

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Brain/Behavior Link

• Our ancestors understood that the brain and
  behavior are linked.
• For example a strong blow to the head can result
  in
• A change of consciousness
• A change in perception
• Memory loss
• Loss of movement

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Correlational Studies

• Psychologists investigate the relationship
  between the brain and behavior by examining what
  happens after the brain is damaged either
  accidentally or deliberately as part of an
  experiment
• Examples include stroke, epileptic seizure or
  head injury
• Studies are correlational because changes in
  behavior are assumed to be related to brain damage

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Trepanation

• 40,000 year-old skulls show evidence that parts
  of the skull were deliberately removed.
• May have been a medical treatment or to release
  evil spirits.
• Sometimes practices by tribal groups in
  religious ceremonies.
• The presence of trepanated skulls does suggest an
  awareness of the link between brain and behavior.

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Observations

• An alternative way of studying brain function is
  to stimulate the brain itself and then observe
  what happens
• Methods include
• Chemical stimulation
• Electrical stimulation
• Magnetic stimulation

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Chemical Stimulation

• Microdialysis a micropipette is used to deliver
  a neurotransmitter into a neuronal synapse
• Can be used in reverse to extract
  neurotransmitters

Dermal microdialysis
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Electrical Stimulation

• Gustav Fritish (1828-1929)
• Eduard Hitzig (1838-1907)
• Hitzig in 1860s worked on patients who had
  pieces of their skulls blown away in battle and
  he stimulated exposed brains with wires connected
  to a battery
• Hitzig discovered weak electric shocks applied to
  areas at the back of the brain, caused the
  patients eyes to move

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Electrical Stimualtion

• Hitzig and Fritsch set up a makeshift lab in
  Fritschs house
• Stimulated the brains of live dogs
• Found that they could cause crude movements of
  the dogs bodies
• Found specific areas of the brain controlled
  specific movements
• Question of ethics in non-human studies

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Electrical Stimualtion

• Wilder Penfield (1891-1976)
• Neurosurgeon specializing in the surgical
  treatment of epilepsy
• Kept his patients awake so they could talk to him
  about what they were feeling as he stimulated
  areas of the brain to locate seizure activity
• Developed a map of the somatosensory cortex
  showing how much space is taken up by the
  different regions of the body the homunculus or
  little man

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Magnetic Stimulation

• Transcranial Magnetic Stimulation
• A magnetic coil is held on the scalp and
  depending on the strength of the current, the
  brain areas can be made more or less active, that
  is, the neurons can be switched on and off
• From this technique functional maps of the brain
  can be generated

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Transcranial Magnetic Stimulation
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Lesion

• A lesion is when a part of the brain is either
  destroyed or its function is disrupted.
• Lesions can occur naturally such as following a
  stroke or after a seizure.

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BRAIN LESIONS

• Some lesions are from brain injury or trauma and
  some experiments have been conducted to
  deliberately lesion a portion of the brain.

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Brain Lesioning

• Some experiments have been conducted to
  deliberately lesion the brain
• Electrodes can be placed in the brain and a
  current applied
• Toxins can be injected into specific brain sites
  using a micropipette

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MAGNETIC RESONANCE IMAGING(MRI)
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Ablation

• Ablation
• is when a part of the brain is removed.
• MRI of normal brain (right) and fluid-filled or
  ablated brain (left).

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Case Studies

• Are useful when there are few examples of a
  particular type of damage
• Case studies can illustrate how we can determine
  brain function by looking at what happens to
  behavior when specific parts of the brain are
  damaged
• Excellent example of a case study is Phineas Gage

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Phineas Gage

• Construction worker who was injured by a tamping
  rod. He recovered from the physical injury, but
  his personality changed.
• The damage to Gages frontal cortex resulted in a
  loss of social inhibitions, which led to
  inappropriate behavior.