plasticity and functional recovery of the brain

• during infancy the brain experiences rapid growth in synaptic connections (15000 at age 2-3 years)(Gopnik et al.). As we age, rarely used connections are deleted and frequently used connections are strengthened (called synaptic pruning). It was once thought these changed were limited to childhood but recent research suggests neural connections can change/be formed at any time due to learning and experience
• plasticity supported by taxi driver study: Maguire et al. found more grey matter in the posterior hippocampus in London taxi drivers than in a matched control group. This part of the brain is linked with the development of spatial and navigational skills. As part of their training, the drivers take a complex test called the knowledge to assess their recall of streets and routes. This learning experience appears to alter the structure of the taxi drivers' brain. The longer they had been in the job, the more pronounced was the structural difference
• Plasticity is supported by research on learning. Draganski et al. imaged the brains of medical students 3 months before and after final exams. Learning induced changes were seen in the posterior hippocampus and the parietal cortex, presumably as a result of learning for the exam
• an important example of neural plasticity is healthy brain areas taking over functions of areas damaged/destroyed. Neuroscientists suggest this process occurs quickly after trauma then slows down at which point the person may require rehabilitative therapy
• the brain is able to rewire and recognise 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
• further structural changes in the brain are:

  • axonal sprouting- growth of are nerve endings which connect with other undamaged cells to form new neuronal pathways
  • denervation super sensitivity- axons that do a similar job become aroused to a higher level to compensate for the ones that are lost
  • recruitment of homologous areas- the opposite side of the brain takes over specific tasks like language production
• One strength of plasticity is that it may be a life long ability. Bezzola et al. demonstrated how 40 hours of golf training produced changes in the neural representations in participants aged 40-60. Using fMRI, motor cortex activity in the novice golfers reduced compared to a control group, suggesting greater efficiency after training. This shows that neural plasticity can continue throughout the lifespan.
• One limitation of plasticity is that there are possible negative behavioural changes. The brain's adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as an increases risk of dementia (Medina et al.). 60-80% of amputees have phantom limb syndrome. This suggests that the brain's ability to adapt to damage is not always beneficial and may lead to psychical and psychological problems
• One strength of functional recovery is its real work application. Understanding plasticity has led to neurohabilitation. Understanding axonal growth encourages new therapies. For example, constraint-induced movement therapy involves massed practice with an affected arm while unaffected arm is restrained. This shows that research into functional recovery helps medical professionals know when interventions can be made
• One limitation of functional recovery is that neural plasticity may be related to cognitive reserve. Schneider et al. looked at the time brain injury patients had spent in education and their chances of disability free recovery. 40% of patients who achieved disability free recovery had more than 16 years of education compared to about 10% of patients who had less than 12 years of education. This suggests that cognitive reserve is a crucial factor in determining how well the brain adapts after trauma