plasticity and functional recovery of the brain after trauma

Question 1

plasticity - brain plasticity

Answer 1

• brain has ability to change throughout life
• during infancy, experiences rapid growth in number of synaptic connections, peaking at about 15,000 per neuron at 2-3 years old (Gopnik et al.)
• this is about twice as many as there are in adult brain
• as we age, starting around the age of 3, rarely-used connections are deleted / masked and frequently-used connections are strengthened (synaptic pruning)
• synaptic pruning enables lifelong plasticity where new neural connections are formed based on new demands on brain
• response to experiences such as demand of environment, learning, or aftermath of trauma such as an accident or illness

Question 2

plasticity - research into plasticity

Answer 2

• Maguire et al. studied brains of London taxi drivers, found significantly more grey matter in the posterior hippocampus than in the control group
• this part of brain is associated with development of spatial and navigational skills
• during training, taxi drivers take a complex text which assesses recall of city streets and possible routes
• found that this learning experience alters structure of brains
• also found that the longer the driver had been in the job, the more pronounced the difference (positive correlation)

AO3 -
- results support existence of plasticity because the brain has changed in response to environmental demand (The Knowledge)
- structural changes in total volume of hippocampus, redistribution of neurons from anterior to posterior over time

• Draganski et al. imaged brains of medical students three months before and after final exam
• learning-induced changes were seen in hippocampus and parietal cortex

Question 3

functional recovery - after brain trauma

Answer 3

• following physical injury or other forms of trauma, unaffected areas of brain are able to adapt and compensate for damaged areas
• functional recovery that may occur is an example of neural plasticity
• healthy brain areas may take over functions of those that are damaged, destroyed or missing
• suggested that this process can occur quickly after trauma (spontaneous recovery) and then slow down after weeks or months, when the individual may then require rehabilitative therapy

Question 4

functional recovery - what happens in the brain during recovery?

Answer 4

• brain is able to rewire and reorganise itself by forming new synaptic connections near areas of damage
• secondary neural pathways that would not typically be used to carry out certain functions are activated to enable functioning to continue

supported by structural changes in brain -
- axonal sprouting - growth of new nerve endings, connect with other undamaged nerve cells to form new pathways
- denervation supersensitivity - when axons that do a similar job become aroused to a higher level to compensate for lost ones, can have negative consequence of oversensitivity to messages such as pain
- recruitment of homologous (similar) areas on the opposite side of the brain - specific tasks can still be performed, eg. if broca’s area was damaged on the left side, the right sided equivalent could carry out its functions, functionality may eventually shift back to the left side

Question 5

evaluation limitation of plasticity - negative plasticity

Answer 5

• may have negative behavioural consequences
• evidence shows that the brain’s adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as an increased risk of dementia
• 60-80% of amputees have been known to develop phantom limb syndrome (continued experience of sensations in missing limb as if it were there)
• these sensations are painful, unpleasant and thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss
• however, mirror-box therapy can be used to help this
• brain’s ability to adapt to damage is not always beneficial

Question 6

evaluation strength of plasticity - age and plasticity

Answer 6

• brain plasticity may be a life-long ability
• in general, plasticity reduces with age, but Ladina Bezzola demonstrated how 40 hours of golf training produced changes in the neural representation of movement in participants aged 40-60
• using fMRI, researchers observed increased motor cortex activity in the novice golfers compared to a control group, suggesting more efficient neural representations after training
• shows that neural plasticity can continue throughout lifespan

Question 7

evaluation strength of plasticity - link to nature / nurture debate

Answer 7

• support NN debate as an interactionist approach
• environment influencing neuronal connections

Question 8

evaluation strength of functional recovery research - real-world application

Answer 8

• understanding processes involved in plasticity has contributed to field of neurorehabilitation
• understanding that axonal growth is possible encourages new therapies to be tried
• constraint-induced movement therapy is used with stroke patients where they repeatedly practise using the affected part of their body, while the unaffected part is restrained
• research into functional recovery helps medical professionals know when interventions need to be made

Question 9

evaluation limitation of functional recovery research - cognitive reserve

Answer 9

• level of education may affect recovery rates
• Eric Schneider revealed that the more time people with brain injuries had spent in education, the greater their chances of a disability free recovery (DFR)

Question 10

evaluation strength of plasticity / functional recovery - hemispherectomies

Answer 10

• people can have a whole hemisphere removed as a result of serious damage or trauma that cannot be resolved any other way
• young girl called Cameron was having lots of seizures that were lateralised in her right hemisphere, had it removed in surgery
• within 3 weeks she was able to walk out of hospital and 7 years on can speak and move perfectly with just a slight weakness on her left side
• shows how well plasticity and functional recovery can work to compensate for damaged or removed areas