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Module 13.1:

Module 13.1:. Module 4.3:. Plasticity after Brain Damage. Lateralization of Function. The Left and Right Hemispheres. Commissure , a set of axons that connects the hemispheres: Corpus callosum Anterior commissure Hippocampal commissure.

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Module 13.1:

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  1. Module 13.1: Module 4.3: Plasticity after Brain Damage Lateralization of Function

  2. The Left and Right Hemispheres Commissure, a set of axons that connects the hemispheres: Corpus callosum Anterior commissure Hippocampal commissure

  3. Lateralization: Division of labor between the two hemispheres

  4. 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

  5. Auditory Connections: Each hemisphere gets information, but contralateral hemisphere pays more attention Auditory Connections to the Hemispheres

  6. Cutting the Corpus Callosum Epilepsy: “Severed Corpus Callosum” video clip (10m): https://www.youtube.com/watch?v=lfGwsAdS9Dc • 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

  7. Functions Associated with the Hemispheres

  8. Development of Lateralization and Handedness Planum temporale: Maturation of the corpus callosum: Occurs gradually over time Young children have more difficulty coordinating limbs • Critical for speech comprehension • Larger in left temporal lobe of 65% of people

  9. 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?v=eoC4PgFsF84

  10. 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

  11. 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

  12. 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

  13. Treatments after Stroke • Tissue plasminogen activator (tPA) breaks up blood clots and reduces the effects of ischemic strokes. • Cooling brain (91-97°F): • 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

  14. Plasticity After Brain Damage • Diaschisis refers to the decreased activity of surviving neurons after damage to other neurons.

  15. 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.

  16. Plasticity After Brain Damage • Collateral sprouts are new branches formed by other non-damaged axons that attach to vacant receptors.

  17. 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.

  18. 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.

  19. 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.

  20. Plasticity After Brain Damage • Deafferenated limbs are limbs that have lost their afferent sensory input.

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