Plasticity and Functional Recovery in the Brain after trauma

• Plasticity


  how flexible the brain is
• Brain Plasticity


  - brain constantly changes in life, due to experiences, practices, training and sometimes injury.

  - very adaptive to new situations.

  - Pruning - connections are lost due to lack of use.

  - Bridging - new connections are created due to use and new stimulus.

  - Gopnick et al - during infancy, brain experiences rapid growth in the number of synaptic connections it has, peaking at age 2-3yrs.
• Is there a limit to Plasticity?

  - it was thought that such changes were restricted to childhood.

  - it was thought the adult brain was fixed in terms of structure and function.

  - research suggests that neural connections, can change at any time in life.

  - continue to gain new neural connections due to learning and experience.
• Maguire et al


  studied the brain of London taxi drivers.

  - results showed the taxi drivers had a higher volume of grey matter in their posterior hippocampus then a control group.

  - area of the brain has been found to be associated with spatial and navigational skills.
• Draganski et al


  Imaged the brains of medical students 3 months before and after their final exams.

  found learning-related changes had occurred in the posterior hippocampus and the parietal cortex.
• Mechelli et al


  compared the brains of bilingual people and matched monolingual controls.

  bilingual ppts had a larger parietal cortex.
• Why do Draganski and Mechelli support plasticity?

  both show the brain has adapted to gain more knowledge. these studies both support plasticity, posterior hippocampus and parietal cortex both have changed to learn a new language and to remember knowledge for their final exams.

  bridging has occurred.
• Functional Recovery of the Brain after Trauma: example of plasticity

  after trauma - unaffected areas that are damaged, destroyed or compensate for the damaged areas.

  functional recovery may occur - example of plasticity.

  - healthy brain areas - take over the function of areas that are damaged, destroyed or even missing.

  - can occur quickly after trauma (spontaneous recovery) and then slow down after weeks/months.

  - rehabilitation may be needed.
• What happens in the brain during functional recovery?

  - brain can rewire itself by forming new synaptic connections close to the damaged area.

  - secondary neural pathways are 'unmasked' to enable function to continue, often in the same way as before (Doidge et al)

  helped by:

  - axonal sprouting: growth of new nerve endings, which connect to undamaged nerve cells to form new neuronal pathways.

  - reformation of blood vessels.

  - recruitment of homologous areas on the opposite sides of the brain: perform specific tasks. e.g. Broca's area on the left side of the brain is damaged, the right-sided equivalent map step in for a while.
• Real Life Example


  Gabby Giffords

  - shot in the head.

  - within months, she made staggering progress.

  - Giffords was able to walk under supervision, with perfect control of her left arm and leg.

  - her progress would place her in the top 5% of people recovering from a serious brain injury.
• Strength - Practical Application off neurohabilitation

  - spontaneous recovery of brain after trauma tends to slow down after a few weeks, so physical therapy may be required to improve functioning.

  - e.g. electrical stimulation or movement therapy. may be used to counter the deficits in cognitive/motor function after a stroke.

  - it has led to the development of therapies and interventions to ensure that functional recovery is always completely successful.
• Weakness - brain's ability to rewire itself can have negative behavioural consequences

  - Ramachandran and Hirstein found that 60-80% of amputees developed phantom limb syndrome.

  - these feelings are problematic for the patient and have been linked back to cortical reorganisation in somatosensory cortex.

  - shows that bridging can result in a negative consequence. negative stimulus can change the brain for the worst.
• Strength - plasticity has been found to continue with age

  - Bezzola et al showed that 40hrs of golf training can lead to increased neural representations of movement.

  - using brain scans it was noticed that there wad reduced motor activity in novice golfers in comparison to a control.

  - shows neural representations become more efficient with training at any age.
• Strength - evidence from animal studies

  - Hubel and Wiesel sewed one eye of a kitten shut and studied the effect on the brains cortical responses.

  - found that the areas of the visual cortex associated with the shut eye continued to process info from the open eye.

  - shows the visual cortex adapted in response to the shut eye to enable info to still be processed.