Plasticity and Functional Recovery of Brain after trauma

Brain plasticity

Brain’s ability to modify its own structure & function as a result of experience & new learning

• Generally involves growth of new connections

During infancy what is happening to synaptic connections?

The brain is experiencing rapid growth of synaptic connections, approx 15,000 at 2-3 yrs

• Twice as much as adult’s

As we age what happens to connections?

Synaptic pruning → Rarely used synaptic connections are deleted, & frequently used ones are strengthened

What is the purpose of synaptic pruning?

To remove unnecessary neuronal structures from brain. By developing new connections & pruning away weak/unnecessary ones, the brain is able to constantly adapt to changing environment

• As we age, it is vital for us to understand more complex matters

• Simpler associations found at childhood are thought to be replaced by complex structures

Who studied neural plasticity? What was the aim?

Maguire (2000)

• Aimed to examine whether structural changes could be detected in brains of people w. extensive experience of spatial navigation

Maguire method

Used MRI scanner to calculate volume of grey matter in brains of London taxi drivers, compared to matched control group

Maguire findings + explanation

Found significantly more grey matter in posterior hippocampus of taxi drivers.

• Positive correlation found between amount of time spent as taxi driver & volume of grey matter in posterior hippocampus

  • That part of the brain associated w. development of spatial + navigation skills

  • increased grey matter in posterior hippocampus of taxi drivers suggests that extensive spatial navigation leads to structural brain changes, supporting the idea that the adult brain is not fixed but can reorganise itself through use.

Maguire Conclusion

Findings support idea of brain plasticity and suggest experience can change the structure of the brain

• Increased grey matter in posterior hippocampus of taxi drivers suggests extensive spatial navigation leads to structural brain changes, supporting the idea that the adult brain is not fixed but can re-organise itself through use.

DIS1: Negative behavioural consequences of brain plasticity

Ev: Brain’s adaptation to prolonged drug use leads to poorer cognitive functioning in later life + increased risk of dementia (Medina). 60-80% of amputees develop phantom limb syndrome, - continued sensations of missing limbs as if it was still there. Sensations usually unpleasant & painful.

Ex: Thought to be due to cortical reorganisation in somatosensory cortex, where areas of brain that previously processed input from missing limb become misinterpreted or reorganised, leading to abnormal sensory experiences (Hirstein)

L: Suggests although brain is adaptable, neuroplasticity can sometimes produce negative outcomes rather than beneficial ones.

AD1: Plasticity is a life-long phenomenon

Ev: (Bezzola) demonstrated how 40 hrs of gold raining produced changes in neural representations of movement in participants aged 40-60. Using fMRI, found increased activity in motor cortex compared to control group

Ex: This suggests repeated practice can lead to functional changes in the brain, making neural representations of movement more efficient through training.

L: Supports idea adult brain remains plastic and can adapt functionally in response to training.

Functional Recovery of the Brain after Trauma

Form of plasticity. The brain’s ability to redistribute or transfer functions usually performed by damaged area(s) to other undamaged area(s)

• Unaffected areas of the brain able to compensate for damaged areas

• Neuroscientists suggest this process occurs quickly after trauma (spontaneous recovery) & slows down after several weeks or months

  • Then individual need rehabilitative therapy to further recovery

What happens to brain duirng recovery?

Brain rewires and re-organizes itself by forming new synaptic connections close to area of damage

Overall, what are the 4 things that happen in the brain during recovery?

1. Neuronal unmasking (which is supported by 2-4)

2. Axon sprouting

3. Denervation supersensitivity

4. Recruitment of similar ares on opp side of brain

Neuronal unmasking

Secondary neural pathways that wouldn’t usually be used to carry out certain functions are activated/unmasked to enable functioning to continue, often in the same way as before

Axonal Sprouting

Growth of new nerve endings which connect w. other undamaged nerve cells to form new neuronal pathways

Denervation supersensitivity

Axons that do similar job become aroused to higher level to compensate for ones lost

• Neg consequences of oversensitivity to messages like pain can arise

Recruitment of homologous areas on opp sides of brain

Brain recruits homologous area(s) from opp side of brain to perform the specific tasks of the damaged area(s)

• After period of time functionality may shift back

AD1: Real-world application

P: Understanding processes involved in plasticity has contributed to neurorehabilitation field.

Ev: Understanding of axonal growth has led to therapies like constraint-induced movement therapy. Used by stroke patients where they repeatedly use affected body part, while unaffected part is constrained

Ex: Suggests knowledge of brain reorganisation can be used to guide effective treatments that promote formation of new neural pathways.

L: Shows that research into functional recovery is useful as it informs practical medical treatments that improve patient outcomes after brain damage.

DIS1: Level of education may influence recovery rates

Ev: Schneider revealed more time people w. brain injury had spent in education, greater chance of disability free recovery (DFR). 40% who had achieved this had more than 15 yrs in education, compared to 10% that had less than 12 yrs.

Ex: Suggests higher education may build cognitive reserve, making brain more able to compensate for damage

L: Limits explanatory power of research into brain recovery after trauma due to possible confounding variables