Plasticity + Functional recovery after trauma

• Plasticity-(neuroplasticity/cortical reopening). The brains tendency to change and adapt (functionally and physically) as a result of experience such as trauma and new learning.
• Functional recovery - form of plasticity following damage through trauma. The brains ability to redistribute or transfer functions cocally performed by damaged area to undamaged areas. (functional reorganisation)
• In infancy, the brain has a rapid growth in the num of synaptic connections: at birth, the number of synapses per neuron is 2,500, but by age two or three, it's about 15,000 per neuron (Gopnick et al 1999).
• As we age, synapses which have rarely been used are lost and those that are used often are strengthened, resulting in the brain becoming a more efficient communication system over time - synaptic pruning. This process is highly active in new borns and children.
• Maguire et al found London taxi drivers to have significantly more grey matter volume in the posterior hippocampus (associated with spatial and navigational skills in humans and other animals) than a matched (age/gender) control group. The longer they had been in the job correlated with the larger the structural difference.This suggests physical structure is plastic. Brain reconfigures to adapt to psych demands, in this case to improve memory formation. MRI? Correlational design?
• Dragnaski et al imaged brains of medical students 3 months before/after final exams. Learning induced chnahes occurred in posterior hippocampus and parietal cortex.   
• Mechelli found larger parietal cortex in brains of bilingual ppl compared to matched monolingual control group.
• Following trauma such as physical injury or stroke, unaffected areas of the brain adapt and compensate for the damaged areas. This functional recovery is an example of neural plasticity.
• Recovery - brain reorgansies/rewires itself by forming new synaptic connections close to damaged area. Secondary neural pathways that would not be typically used to carry certain functions as activated to enable functioning to continue (Doidge)  
• Supporting structural changes for Doidge:

  • Axonal sprouting - the growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways. Neural regeneration is the growth of new neuronal cells.
• Supporting structural changes for Doidge:

  • Denervation - reformation of blood vessels
• Supporting structural changes for Doidge:

  • Recruitment of homolgous areas - on opposite side of brain to perform specific tasks. So if Broca's area was damaged on the left side of the brain, the right sided equivalent would carry out its function. Functionality may then shift back to the left side in the future
• Denervation supersensitive - Phenomenon that occurs when neurons are lost causing post-synaptic membrane to Dev more receptors for neurotransmitters in order to compensate. Increased receptor density leads to supersensitivity in denervation stage
• S - Important practical applications: neurohabilitation. following brain trauma spontaneous recovery slows down after a few weeks so physical therapy may be needed to maintain any improvements. For example, rehabilitative therapy, electrical stimulation of the brain to counter motor/cognitive deficits. The brain has the capacity to 'fix' itself but with our knowledge we understand that further intervention is needed to maximise success.
• Brain's ability to rewire itself can also have maladaptive consequences:

  • Extensive drug use can lead to deficits in cognitive functioning, and higher risk of dementia in layer lfie (Medina et al)
  • 60-80% of amputees Dev phantom limb syndrome. Thought to be due to cortical reorganisation in somatosensory cortex as a result of limb loss (Ramachandran and Hirstein)
• Functional plasticity declines with age. The brain has a natural tendency for reorganisation in childhood as it is constantly adapting to new experiences and learning.
• Bezzola et al (2012) showed how 40 hours of golf training produced changes in neural representation of movement in p's aged 40-60. An experimental (golf novice) and control group were scanned using fMRI during kinetic motor imagery of their golf swing, prior to and following golf training (with the control group matched for average pre- to post-test duration). researchers observed reduced motor cortex activity only in the novice golfers compared to control group. Findings suggest more efficient neural representations after training. shows neural plasticity continues throughout life span.
• Cognitive reserve is a neuroscientific term used to describe individual differences in susceptibility to age-related brain changes, and how tasks are performed that may allow some people to be more resilient than others. This is supported by Mathias meta analysis. Found IQ and educational background are positively correlated with better outcomes after traumatic brain injury suggesting some individuals have greater cog reserve helping recovery.
• Meditation and mindfulness may change the structure and function of the brain. This is supported by Tang et al who found that four weeks of meditation led to an increase in white matter in the anterior cingulate cortex, which contributes to self-regulation and control.
• What did Lazar et al. (2005) use to show differences in brain structure between meditators and non-meditators?


  MRI's
• What was observed about the cortex of experienced meditators compared to non-meditators?


  Experienced meditators had a thicker cortex
• In which areas was the thicker cortex observed in experienced meditators?


  In areas related to attention and sensory processing
• What was the duration of the mindfulness-based course mentioned in Holzel et al. (2011)?


  8 weeks
• What increase in brain structure was observed after the mindfulness-based course?

  An increase in grey matter in the left hippocampus
• What is the left hippocampus associated with?


  Learning and memory
• What are the key findings of Lazar et al. (2005) regarding experienced meditators?


  • Thicker cortex than non-meditators
  • Thicker cortex observed in areas related to attention and sensory processing
• What are the effects of an 8-week mindfulness-based course according to Holzel et al. (2011)?


  • Increase in grey matter in the left hippocampus
  • Associated with learning and memory
• Plasticity can lead to neuronal cell death as a result of the brain changing significantly and relatively quickly to compensate for permanently damaged areas.
• Factors affecting FC - women are able to recover greater following brain damage than men. Rehabilitative therapy where focused efforts lead to an improvement in results.