Placiticity and functional recovery of the brain after trauma

Brain placticity (1)

The brain would appear to be ‘plastic’ in the sense that it has the ability to change throughout life.

 

During infancy, the Brain experiences a rapid growth in the number of synaptic connections it has, peaking at about 15,000 per neuron at two to three years of age. This is about twice as many neurons as there are in the adult brain.

 

As we age, rarely used connections are deleted and frequently used connections are strengthened - a process known as synaptic pruning.

 

People once though that the adult brain was not capable of change but we now understand that synaptic pruning enables lifelong plasticity where new neural connections are formed in response to new demands in the brain.

Research into placicticty

Eleanor maguire (2000) 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.

 

This part of the brain is associated with the development of spatial and navigational skills In humans and other animals. As part of their training, London cabbies must take a complex test called ‘The Knowledge’, which assesses their recall of the city streets and possible routes.

 

Maguire presumed that this learning expereince altered the structure of the taxi drivers’ brains. In addition to this, the longer the taxi drivers has been in the job, the more pronounced was the structural difference (positive correlation).

 

A similar finding was observed by draganski, who imaged the brains of medical students three months before and after their final exams.

• Changes (presumably due to learning) where seen in the posterior hippocampus and the parietal cortex.

Placticity a03 - strength

Age and Placiticty

One strength is that brain placiticty  may be a lifelong ability.

 

In general placticity reduces with age. However Bezzola (2012) Demonstrated how 40 hours of golf training produced changes in the neural representations of movement in participants aged 40-60.

 

Using fMRI, the researchers observed reduced motor cortex activity in the novice golfers compared to a control group, suggesting more efficient neural representations after training.

 

This shows that neural placiticity can continue throughout the lifespan.

Placticity a03 - weakness

Negative placiticity

One limitation of placticity is that it mat have negative behavioural consequences. 

 

Evidence has shown that the brain’s adaptations to prolonged drug use leads to poorer cognitive functioning in later life, as well as an increased risk of dementia. (Medina)

 

Also, 60-80% of amputees have been known to develop phantom limb syndrome - the continued expereince of sensations in the missing limb as if it were still there.

 

These sensations are usually unpleasant, painful and are thought to be due to reorganisation in the somatosensory cortex that occurs as a result of limb loss.

 

This suggests that the brains ability to damage is not always beneficial

Functional recovery after brain trauma

Following physical injury or other forms of trauma (such as experiencing a stroke), unaffected areas of the brain are often able to adapt and compensate for those areas that are damaged.

 

The functional recovery that may occur in the brain trauma is an example of neural placitocty.

 

Healthy brain areas may take over the functions of those areas that are damaged, destroyed or even missing.

 

Neuroscientists suggest that this process can occur quickly after trauma (spontaneous recovery) and it then slows down after several weeks or months. At this point the individual may require rehabilitative therapy to further their recovery.

What happens in the brain during recovery (1)

The brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of damage (a bit like avoiding roadworks on the way to school by finding a route).

 

Secondary neural pathways that would not typically be used to carry out certain function s are activated or ‘unmasked’ to enable functioning to continue (Doidge 2007).

 

This process is supported by a number of structural changes in the brain including:

What happens in the brain during recovery (1)

• Axonal sprouting = the growth of new nerve endings which connect with other nerve cells to form new neuronal pathways.

• 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 negative consequence of oversenenitivity to messages such as pain.

• Recruitment of homologous (similar) areas on the opposite side of the brain = this means specific tasks can still be performed. An example would be if Broca’s area was damaged on the left side of the brain, the right sided equivient might carry out its functions. After a period of time, functionality may then shift back to the left side.

Functional recovery a03 - strength

Real- world application

 

One strength of functional recovery research is its real-world application.

 

Understanding the processes involved in plasticity has contributed to the field of neurorehabilitation.

 

Simply understanding that axonal growth is possible encourages new therapies to be tried.

 

For example, constraint-induced movement therapy is used with stroke patients whereby they repeatedly practice using the affected part of their body (such as an arm) while the unaffected arm is restrained.

 

This shows that research into functional recovery is useful as it helps medical proffesionals.

Functional recovery a03 - limitation

Cognitive reserve

 

One Limitation of functional recovery is that level of education may influence recovery rates.

 

Erin Schneider (2014) revealed that the more time peole with a bran injury had spent in education - taken as an indication of their ‘cognitive reserve’ - the greater their chances of a disability-free recovery (DFR).

 

40% of those who achiever DFR had more than 16years’ of education compared to about 10% of those who has less than 12 years education.

 

This would imply that people with brain damage who have insufficient cognitive reserve are less likely to achieve a full recovery.