plasticity and functional recovery of the brain

• The brain is ‘plastic’: (P)

  • During infancy = the brain experiences a rapid growth in synaptic connection (peaking at about 15,000 at age 2-3 years)
  • As we age = rarely-used connections are deleted and frequently-used connections are strengthened (called synaptic pruning)
  • It was once thought 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
  • neuroplacticity = is this ability of the brain to change its physical structure to perform different functions
• concept of plasticity = supported by Maguire et al (taxi driver study): (P)

  • He found significantly more volume of grey matter in the posterior hippocampus in London taxi drivers than in a matched control group
  • posterior hippocampus = linked with the development of spatial and navigational skills
  • As part of the training = London taxi drivers 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 the taxi drivers brains
  • The longer they had been in the job, the more pronounced was the structural difference
• plasticity supported by research on learning (P)

  • Draganski et al = 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 learning for the exam
• limitation of plasticity = possible negative behavioural consequences (P)

  • Medina et al = the brain’s adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as increased risk of dementia
  • 60-80% of amputees have phantom limb syndrome = experiencing sensations in missing limb due to changes in somatosensory cortex
  • Suggests that the brain‘s ability to adapt to damage is not always beneficial and may lead to physical and psychological problems
• strength of plasticity = may be a life-long ability (P)

  • 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 golfers reduced compared to a control group (suggesting greater efficiency after training)
  • Shows that neural plasticity can continue throughout the lifespan
• extra evaluation for plasticity = seasonal brain changes (P)

  • Seasonal plasticity occurs in response to environmental changes
  • Eg = the SCN shrinks in the spring and expands in the autumn
  • BUT = much of the work on seasonal plasticity has been done on animals (mainly songbirds) - human behaviour may be controlled differently
  • Suggests that animal research may be a useful starting point but can’t simply be generalised to humans
• Following trauma = unaffected areas of the brain take over lost functions (FRAT)

  • Functional recovery of the brain after trauma (an important example of neural plasticity) = healthy brain areas take over functions of areas damaged, destroyed or even missing
  • Neuroscientists suggest 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 (FRAT)

  • 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 (FRAT)

  • Axonal sprouting = growth of new 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 (similar) areas = the opposite side of the brain takes over specific tasks (eg language production)
• strength of functional recovery = RWA (FRAT)

  • Understanding plasticity has led to neurorehabilitation (understanding axonal growth encourages new therapies)
  • Eg = constraint-induced movement therapy involves massed practice with an affected arm while unaffected arm is restrained
  • Shows that research into functional recovery helps medical professionals know when interventions can be made
• limitation of functional recovery = neural plasticity may be related to cognitive reserve (FRAT)

  • Schneider et al = looked at the time brain injury patients had spent in education (indicated their cognitive reserve) and their chances of a disability-free recovery (DFR)
  • 40% of patients who achieved DFR had more than 16 years’ education compared to about 10% of patients who had less than 12 years’ education
  • Suggests that cognitive reserve is a crucial factor in determining how well the brain adapts after trauma
• extra evaluation for functional recovery = supporting evidence uses small samples (FRAT)

  • Research on new treatments (eg Banerjee) showed total recovery from a stroke using stem cell treatment compared to normal 4% recovery
  • BUT = this study Dre conclusions based on just 5 participants and no control group (typical of research on functional recovery)
  • This research may lack validity, but waiting for larger samples may prevent the development of valuable treatments