Plasticity and functional recovery

What is plasticity?

Plasticity is the brains ability to change an adapt as a result of damage, experiences and new learning

synaptic pruning

During infancy the brain grows in the number of synaptic connections (peaks to 15 000 by 3 years old- ish). This is twice as many as in the adult brain. As we age, rarely used connections are deleted and frequently used connections are strengthened, this is called synaptic pruning. 

How does plasticity disprove the critical period

• Originally it was thought that changes were restricted to developing the brain within childhood and that the adult brain, having moved beyond a critical period, would remain fixed and static in terms of function and structure.

• Recent research suggests that at any time in life existing neural connections can change and new ones can be formed as a result of learning and the environment.

• The brain can change and adapt as a result of new experiences and new learning, and is not predetermined/ innate as previously suggested by other explanations (Localisation to name one!).

DRAGANSKI (2006) aim

Does extensive learning induce structural changes in the cortex of brains and are these changes  long or short term?

DRAGANSKI method

Sample: 38 medical students & 12 control students
MRI Scans of the brain were taken 3 months before medical exams, on the 1st or 2nd day of the exam and 23 of the participants  had a scan 3 months later.

DRAGANSKI results

significant increase in the grey matter of the Posterior Parietal Cortex of the medical students during the exam period and remained. Increase in posterior hippocampus, which continued increasing even after the learning period had cease

DRAGANSKI conclusion

This research provides support that plasticity can occur as a result of changes within the environment to help cope with these kinds of changes.

Maguire (2000) aim

To find out if there was a difference in the brain scans of taxi drivers (with extensive spatial knowledge) compared to a control group of non taxi drivers.

Maguire method

-16 Right handed licensed London taxi drivers & 50 non taxi driving right handed males.
IV- Taxi driver or not Taxi driver
DV- MRI Scans were taken, analysed and compared

Maguire results

No differences in the overall volume of Hippocampus, but the Anterior Hippocampal Volume was bigger in the control group and the Posterior Hippocampal Volume bigger in Taxi Drivers. It was also found that the amount of time as a Taxi Driver was positively correlated with the volume of the Posterior Hippocampus.

Maguire conclusion

Provides evidence of regional plasticity (restructuring) in the brain of a healthy adult as a result of extensive learning and environmental stimulus

Functional recovery

• After physical injury or trauma (stroke), unaffected areas of the brain are able to adapt and compensate for damaged areas.

• Functional recovery that may occur in the brain after trauma is an example of plasticity. 

• Healthy brain areas may take over functions of those that are damaged . Neuroscientists say this can happen very quickly (spontaneous recovery) but can then slow down which is when a patient may need rehabilitation to help encourage the functional recovery along.

4 types of functional recovery

• Axonal sprouting

• Angiogenesis

• Recruitment of homologous areas

• Neural unmasking

Axonal sprouting

When a neuron is damaged or dies, nearby healthy neurons can grow new branches (axons) to form connections with neurons that have lost their input. Think of it like a road network: A major road is closed due to an accident. New side roads are built. Traffic is redirected around the damaged area

Angiogenesis – Reformation of blood vessels

Following brain injury, the body may create new blood vessels around damaged areas. New neurons and new neural connections are more likely to survive if they receive adequate resources.

Recruitment of homologous areas

where an area has been damaged the opposite side of the brain may take on those abilities.

Neural unmasking

The brain already contains many connections that are present but inactive or inhibited. When damage occurs, these dormant pathways can suddenly become active.

Evaluation of Plasticity and Function Recovery - Scientific credibility for plasticity

Research from Maguire and Draganski (mentioned earlier) support the idea that the structure of our brains can change and adapt to the environmental pressures it is put under. This is still classed as nature, as it is still the anatomical structure that is causes the changes in our behaviour, however you could definitely mention that it contributes towards the nature vs nurture debate and suggests a more varied interactionist approach is adopted when thinking about human behaviour.

Case studies give credibility  to functional recovery

The case study of Jodie suggests that our brains do change and adapt to cope with the damage and loss of function caused from removing parts of the brain. You could also bring in that this suggests this is a more holistic explanation of how our brains affect our behaviour compared to Localisation theory which suggests that all function would be lost.

Practical application of the findings to the field of neurorehabilitation

Understanding the processes of plasticity and functional recovery led to the development of neurorehabilitation which uses motor therapy and electrical stimulation of the brain to counter the negative effects and deficits in motor and cognitive functions following accidents, injuries and/or strokes. This demonstrates the positive application of research in this area to help improve the cognitive functions of people suffering from injuries.

Dispute over age and plasticity

Some evidence argues that the older you are, the less plasticity your brain can do:

Marquez da la Plata et al (2008)
Following brain trauma, older patients (40+ years old) regained less function in treatments than younger patients. They were also more likely to decline in terms of function for the 5 years following the trauma.

However, the following research says otherwise. Potentially, individual differences play more of a part in plasticity than the theory gives credit too. Suggesting that there may be more to the explanation that it gives.

rehabilitation principles:

specify, intensity, repetition, use or loose it