Plasticity and functional recovery of the brain

Cards (10)

  • The brain is 'plastic' - synaptic connections form and are pruned.
    During infancy, the brain experiences a rapid growth in synaptic connections, peaking at about 15,000 at age 2-3 (Gopnick).
    As we age, rarely used connections are deleted and the frequently used are strengthened - synaptic pruning.
    It was once thought that these changes were limited to childhood. But recent research suggests neural connections can change or be formed at any time, due to learning and experience.
  • The concept of plasticity is supported by studies.

    Maguire found significantly more volume of grey matter in the posterior hippocampus in London taxi drivers than in a control group. This part of the brain is linked with the development of spatial and navigational skills.
    As part of their training, cabbies take a complex test called 'The Knowledge' to assess their recall of city streets and possible routes. This learning experience appears to alter the structure of taxi drivers' brains - the longer they had been in the job, the more pronounced was the structural difference.
  • Plasticity is also supported by other research.

    Draganski imaged the brains of medical students three months before and after final exams. Learning-induced changes were seen in the posterior hippocampus and the parietal cortex, presumably as a result of the exam.
  • Following trauma, unaffected areas of the brain take over lost functions.
    Functional recovery of the brain after trauma is an important example of neural plasticity - healthy brain areas take over functions of areas damaged, destroyed or even missing.
    Neuroscientists suggests this process occurs quickly after trauma (spontaneous recovery) and then slows down - at which point the person may require rehabilitative therapy.
  • The brain 'rewires' itself by forming new synaptic connections.

    The brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of damage.
    Secondary neural pathways that would not typically be used to carry out certain functions are activated or 'unmasked' to enable functioning to continue.
  • Structural changes in the brain (e.g. axonal sprouting).

    Further structural changes may include:
    • Axonal sprouting - growth of new nerve endings which connect with other undamaged cells to form new neuronal pathways.
    • Reformation of blood vessels.
    • Recruitment of homologous areas on the opposite side of the brain to perform specific tasks.
  • One strength of plasticity and recovery research is its practical application. 

    Understanding processes in plasticity has contributed to the field of neurorehabilitation. Techniques include movement therapy and electrical stimulation of the brain to counter deficits to cognitive functioning experienced following a stroke. This shows that although the brain may have the capacity to 'fix itself' to a point, this process requires further intervention if it is to be successful.
  • One limitation is neural plasticity may be related to cognitive reserve.
    Evidence suggests a person's educational attainment may influence how well the brain functionally adapts after injury. Schneider found the more time brain injury patients had spent in education, the greater their chances of a disability-free recovery. This suggests that cognitive reserve is a crucial factor in determining how well the brain adapts after trauma.
  • Another limitation is that the relationship between age and plasticity is complex.
    Functional plasticity tends to reduce with age. The brain has a greater propensity for reorganisation in childhood as it constantly adapts to new experiences and learning. However, Bezzola demonstrated how 40 years of golf training produced changes in the neural representation of movement in participants ages 40-60. This shows that neural plasticity does continue throughout our lifespan.
  • One strength is further support for neural plasticity from animal studies. 

    Hubel and Wiesel sewed one eye of a kitten shut and analysed the brain's cortical responses. The are of the visual cortex associated with the shut eye was not idle but continued to process information from the open eye. The pioneering study demonstrated how loss of function leads to compensatory activity in the brain - evidence of neural plasticity.