Module 13.1:

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• Module 13.1

• Module 4.3

• Plasticity after Brain Damage

• Lateralization of Function

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The Left and Right Hemispheres

• Commissure, a set of axons that connects the
  hemispheres
• Corpus callosum
• Anterior commissure
• Hippocampal commissure

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Lateralization Division of labor between the two
hemispheres
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Visual Field What is visible at any momentLeft
and right visual fields Each processed in
contralateral hemisphereOptic chiasm where
crossover of info occurs
Visual Connections to the Hemispheres
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Auditory Connections Each hemisphere gets
information, but contralateral hemisphere pays
more attention
Auditory Connections to the Hemispheres
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Cutting the Corpus Callosum

• Epilepsy

• A condition involving excessive, synchronized
  neural activity
• Seizure Behavioral symptom, can range from mild
  to severe
• Focus Point in brain where seizure begins
• Commissurotomy Severing of the corpus callosum
• Split-brain patient has undergone a
  commissurotomy

• Severed Corpus Callosum video clip (10m)

• https//www.youtube.com/watch?vlfGwsAdS9Dc

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Functions Associated with the Hemispheres
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Development of Lateralization and Handedness

• Maturation of the corpus callosum

• Planum temporale

• Critical for speech comprehension
• Larger in left temporal lobe of 65 of people

• Occurs gradually over time
• Young children have more difficulty coordinating
  limbs

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Plasticity After Brain Damage

• Survivors of brain damage show subtle to
  significant behavioral recovery.
• Video clip from The Secret Life of the Brain,
  The Aging Brain (2002)
• https//www.youtube.com/watch?veoC4PgFsF84

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Plasticity After Brain Damage

• Possible causes of brain damage include
• tumors
• infections
• exposure to toxic substances
• (a) Brain of a person who died immediately after
  a stroke. Note the swelling on the right side.
  (b) Brain of a person who survived for a long
  time after a stroke. Note the cavities on the
  left side, where many cells were lost. (c) Brain
  of a person who suffered a gunshot wound and died
  immediately.

• degenerative diseases
• closed head injuries
• stroke

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Plasticity After Brain Damage

• Stroke (cerebrovascular accident, CVA)
• temporary loss of blood flow to the brain
• common cause of brain damage in the elderly
• Types of strokes include
• Ischemia -most common type of stroke
• Hemorrhage -less frequent type of stroke

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Plasticity After Brain Damage

• Ischemia and hemorrhage also cause
• Edema-the accumulation of fluid in the brain
• increases pressure on the brain
• increases the probability of further strokes
• kills neurons

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Treatments after Stroke

• Tissue plasminogen activator (tPA) breaks up
  blood clots and reduces the effects of ischemic
  strokes.
• Cooling brain (91-97F)
• less activity
• lower energy needs
• less risk of overstimulation
• Cannabinoids
• minimize cell loss after brain damage by
  decreasing the release of glutamate.
• Excess glutamate may result in the
  over-excitation of neurons

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Plasticity After Brain Damage

• Diaschisis refers to the decreased activity of
  surviving neurons after damage to other neurons.

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Plasticity After Brain Damage

• Damaged axons do grow back under certain
  circumstances.
• PNS axon grows back at a rate of about 1 mm per
  day.

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Plasticity After Brain Damage

• Collateral sprouts are new branches formed by
  other non-damaged axons that attach to vacant
  receptors.

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Plasticity After Brain Damage

• Denervation supersensitivity- the heightened
  sensitivity to a neurotransmitter after the
  destruction of an incoming axon and usually a
  result of increased receptors.

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Plasticity After Brain Damage

• Phantom limb refers to the continuation of
  sensation of an amputated body part and reflects
  this process.
• The cortex reorganizes itself after the
  amputation of a body part by becoming responsive
  to other parts of the body.

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Plasticity After Brain Damage

• Phantom limb can lead to the feeling of
  sensations in the amputated part of the body when
  other parts of the body are stimulated.

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Plasticity After Brain Damage

• Deafferenated limbs are limbs that have lost
  their afferent sensory input.