brain plasticity and functional recovery

• brain plasticity and recovery after trauma

  • the brain is not a static organ, and then functions and processes of the brain can change as a result of experience and injury
  • brain plasticity refers to the brains ability to change and adapt because of experience
  • the brain continues to create new neural pathways and alter existing ones in response to changing experience
• maguire et al


  maguire et al:

  • studied the brains of london taxi drivers and found significantly more volume of grey matter in the posterior hippocampus than in a matched control group
  • its part of their training they are assessed on their ability to recall streets and possible routes
  • the results of this learning experience is to alter the structure of their brains. the longer they had been in the job, the more pronounced was the structural difference
• functional recovery


  the brain also appears to show evidence of functional recovery:

  • the transfer of functions from a damaged area of the brain after trauma to the undamaged areas
• functional recovery - 1. neuronal unmasking

  neuronal unmasking:

  • the brain can perform functional recovery by a process termed neuronal unmasking where 'dormant' synapses (which have not received enough input to be active) open connections to compensate for a nearby damaged area of the brain
  • this allows new connections in the brain to be activated thus recovering any damage occurring in specific regions
• functional recovery - 2. increased brain stimulation

  increased brain stimulation:

  • as neurons are damaged, there is an effect on neighbouring neurons as they no longer have any input
  • this happens with brain hemispheres as well, for example if a person has had a stroke, therefore, both hemispheres end up affected
  • research has suggested that by stimulating the undamaged hemisphere, it can help recovery in regaining some function
• functional recovery - 3. axon sprouting

  • when an axon is damaged, it affects its connection with neighbouring axons
  • in some cases, axons sprout extra connections to the neuron, replacing the ones that have been destroyed
  • if this happens, it will be within weeks of the injury
  • it only works if the damaged axon and the neighbouring compensatory axons do a similar job, otherwise function is not improved
• functional recovery - denervation supersensitivity

  • this occurs when axons that do a similar job become aroused to a higher level to compensate for the ones that are lost
  • however, it can have the consequence of being more over-sensitive to sensations such as pain
• brain recovery 


  the brain, through intensive rehabilitation, can learn to compensate for function

  • the brain can be taught to learn how to use the working faculties and function to compensate for the ones that are lost forever
  • reformation of blood vessels
  • recruitment of homologous (similar) areas
• evaluation - practical application

  practical application:

  • understanding the processes involved in plasticity has contributed to the field of neurorehabilitation
  • this has lead to therapy techniques, such as, movement therapy and electrical stimulation of the brain to counter the deficits in motor/cognitive functioning
  • 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 completely successful
• evaluation - negative plasticity

  negative plasticity:

  • the brains ability to rewire itself can sometimes have maladaptive behavioural consequences
  • prolonged drug use, for instance, has been shown to result in poorer cognitive functioning as well as an increased risk of dementia later in life
• evaluation - age and plasticity

  age and plasticity:

  • functional plasticity tends to reduce with age
  • the brain has a greater propensity for reorganisation in childhood as it is constantly adapting to new experiences and learning
• factors affecting recovery of the brain after trauma - perseverance

  perseverance:

  • taub and berman:
  • shows that when a monkey has a 'deafferated' limb (limb has lost sensory input), it will try not to use it
  • however, if the functioning of the other limbs become damaged, then it will have no option than to use the deafferated one
• factors affecting recovery of the brain after trauma - physical exhaustion, stress and alcohol consumption

  physical exhaustion, stress and alcohol consumption:

  • fleet and heilman:
  • when function is used with considerable effort and although the person can do a task they are often fatigued by the effort
  • stress and alcohol consumption can affect the ability to use any function that has been regained
• factors affecting recovery of the brain after trauma - age

  age:

  • corkin et al:
  • there is a deterioration of the brain in old age and thus therefore affects the extent and speed of recovery
• factors affecting recovery of the brain after trauma - gender

  gender:

  • there is evidence to suggest that women recover better from brain injury as their function is not as lateralised (concentrated in one hemisphere)
  • ratcliffe et al:
  • examined 325 patients with brain trauma for their level of response for cognitive skills to rehabilitation
  • the patients were 16-45 years old at injury, recieved rehabilitation at a car facility, and completed a follow-up one year later
• factors affecting recovery of the brain after trauma - gender - ratcliffe et al

  ratcliffe et al:

  • when assessed for cognitive skills, women performed significantly better than men on tests of attention/working memory and language whereas men outperformed females in visual analytic skills
• factors affecting recovery of the brain after trauma - level of education

  level of education:

  • schneider et al:
  • investigated whether time spent in education would be a factor in recovery from brain injury
  • 769 who had suffered head injuries from road traffic accidents and falls were studied
  • 39% of graduates made a full recovery, whereas, 10% of those who left school early made a full recovery
  • those results arose likely due to the more educated people making more effective use of their brain, which strengthens them
• factors affecting recovery of the brain after trauma - levels of education - schneider et al

  schneider et al:

  • people who have remained in education for longer have a greater 'cognitive reverse', which means they are less likely to be left permanently disabled after a head injury
  • their brains are better able to maintain function in spite of damage, which makes the more likely to regain function following a brain trauma
• difference between plasticity and functional recovery

  plasticity:

  • the brains tendency to change and adapt as a result of experience and new learning

  functional recovery:

  • a form of plasticity that follows damage through trauma
  • it is the brains ability to redistribute or transfer functions usually performed by a damaged area to other undamaged area