Plasticity and functional recovery

• Plasticity= describes the brains tendancy to change and adapt as a result of experience and new learning. Generally involves the growth of new connections.
• Brain plasticity

  During infancy, brain experiences a rapid growth in the number of synaptic connections (peak at 15,000 per neurone at 2-3 years)

  As we age rarely used connections are deleted and frequently used connections are strengthened= synaptic pruning

  Synaptic pruning enables lifelong plasticity where now neural connections are formed in response to demands on the brain.
• Research- Maguire procedure

  Maguire studied brains of London taxi divers and found significantly more volume of grey matter in the posterior hippocampus than in a matched control group.

  • This part of the brain is associated with the development of spatial and navigational skills.
  • As part of training, London cabbies must take a complex test which assesses their recall of city streets and routes.
• Research Maguire findings

  Maguire found this learning experience alerts the structure of the taxi divers brain

  Also found that the longer the taxi diver had been in the job the more pronounced was the structural difference.
• Research- draganski

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

  Learning induced changes were seen to have occured in the posterior hippocampus and parietal cortex.
• Evaluation- negative plasticity

  Limitation= plasticity may have negative behavioural consequences.

  • Evidence has shown that the brains adaptation to prolonged drug use leads to poorer cognitive functioning in later life, and an increased risk of dementia.
  • 60-80% of amputees have been know to develop phantom limb syndrome the continued experience of sensations in the missing limb. They are due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss.
  • Suggest brains ability to adapt to damage isn't always beneficial.
• Evaluation- age and plasticity

  Strength= brain plasticity may be a life long ability.

  • In general plasticity reduces with age.
  • Bezzola demonstrated how 40 hours of golf training produced changes in the neural representations of movement in participants aged 40-60.
  • Using fMRI the researchers observed increased motor efficient neural representation after training.
  • Shows that neural plasticity can continue throughout the lifespan.
• functional recovery= form of plasticity. Following damage through trauma, the brains ability to redistribute or transfer functions usually performed by a damaged area to other undamaged areas.
• What happens in the brain during recovery

  • Brain is able to rewire and recognise itself by forming new synaptic connections close to area of damage.
  • Secondary neural pathways are activated to enable functioning to continue.
• Structural changes in the brain

  • Axonal sprouting
  • Denervation supersensitivity
  • Recruitment of homologous areas on opposite sides of the brain.
• Axonal sprouting= growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways.
• Denervation supersensitivity= occurs when axons that do a similar job become aroused to a higher level to compensate for ones that are lost. However it can have negative consequences of over sensitivity to pain.
• Recruitment of homologous areas= specific tasks can still be performed. Eg: if broca's area was damaged on left side, the right sided equivalent would carry out its functions.
• Evaluation- real world application

  Understanding process of plasticity has contributed to field of neuro rehabilitation.

  • Understanding that axonal growth is possible encourages trial of new therapies.
  • Eg: constraint induced movement therapy is used with stroke patients whereby they repeatedly practice using the affected part of the body while unaffected part is restrained.
  • Shows research into functional recovery is useful as it helps medical professionals know when interventions need to be made.
• Evaluation- cognitive reserve

  Limitation= level of education may influence recovery rates

  • Schneider revealed that the more time people with a brain injury had spent in education the greater their chances of a disability-free recovery.
  • 40% of those who achieved a disability free recovery had more than 16 years education compared to 10% of those who had less than 12 years education.
  • Implies that people with brain damage who have insufficient disability free recovery are less likely to achieve a full recovery.