plasticity and functional recovery of brain after trauma

• plasticity -

  describes the brains tendency to change and adapt as a result of experience and new learning - generally involves growth of new connections
• brain plastcity -

  • gopnick et al (1999) infancy - brain experiences rapid growth in number of synaptic connections - 15,000 per neurone at 2-3 years - nearly twice as many as adult brain
  • synaptic pruning - rarely used connections are deleted and frequently used connections are strengthened - enables lifelong plasticity where new neural connections are formed in response to new demands on the brain
• research into plasticity -

  • Maguire et al (2000) studied brains of London taxi drivers - found significantly more volume of grey matter in posterior hippocampus than in a matched control group
  • this part of brain is associated with development of spatial and naviagtional skills
  • London cabbies must take test 'the knowledge' - Maguire found this learning experience alters structure of taxi drivers brains - found that the longer the taxi drivers had been in the job, the more pronounced the structural difference (positive correlation)
• functional recovery -

  • form of neural plasticity
  • following damage through trauma, the brains ability to redistribute or transfer functions usually performed by a damaged area to other damaged areas
  • neuroscientists suggests this process can occur quickly after trauma (spontaneous recovery) and then slow down after several weeks or months - may then require rehabilitative therapy to further their recovery
• what happens in brain during recovery -

  • brain rewires and reorganises itself by forming new synaptic connections close to area of damage
  • secondary neural pathways that wouldn't be typically used to carry out certain functions are activated or 'unmasked' to enable functioning to continue often in the same way as before
  • process supported by structural changes
• structural changes in brain to enable functioning after trauma -

  • 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 the ones that are lost - negative consequence of oversensitivity to messages eg pain
  • recruitment of homologous areas = similar areas on opposite side of brain - means specific tasks can still be performed eg Broca's area
• evaluation of plasticity: negative plasticity (limitation) -

  • P: may have negative behavioural consequences
  • E: Medina et al (2007) brains adaption to prolonged drug use leads to poorer cognitive functioning later in life + increased risk of dementia
  • E: Ramachandran + Hirstein (1998) 60-80% of amputees known to develop phantom limb syndrome - due to cortical reorganisation in somatosensory cortex as a result of limb loss
  • L: suggests brains ability to adapt to damage is not always beneficial
• evaluation of plasticity: age and plasticity (strength) -

  • P: brain plasticity may be life long ability
  • E: Bozzola et al (2012) demonstrated how 40 hours of golf training produced changes in neural representations of movement in participants aged 40-60 - using fMRI researchers observed increase motor cortex activity in the novice golfers compared to a control group - suggesting more efficient neural representations after training
  • P: shows neural plasticity can continue throughout lifespan
• evaluation of functional recovery: real world application (strength) -

  • P: understanding the processes involved in plasticity has contributed to field of neurorehabilitation
  • E: understanding that axonal growth is possible encourages new therapies to be tried
  • E: eg constraint-induced movement therapy is used with stroke patients whereby they repeatedly practise using the affected part of their body (eg arm) while unaffected part is restrained
  • P: shows that research into functional recovery is useful as it helps medical professionals know when interventions need to be made
• evaluation of functional recovery: cognitive reserve (limitation) -

  • P: level of education may influence recovery rates
  • E: Schneider et al (2014) revealed the more time people with a brain injury had spent in education (indication of their 'cognitive reserve') the greater their chances of disability-free recovery (DFR)
  • E: 40% of those who achieved DFR had more than 16 years education compared to about 10% of those who had less than 12 Yeats
  • L: implies that people with brain damage who have insufficient DFR are less likely to achieve a full recovery