Biopsychology: Plasticity and functional recovery of the brain Flashcards
What is brain plasticity?
Refers to the brain’s ability to change and adapt as a result of experience.
What is functional recovery?
Functional recovery is the transfer of functions from a damaged area of the brain after trauma, to other undamaged areas.
Explain brain plasticity.
The brain would appear to be ‘plastic’ in the sense that it has the ability to change throughout life. During infancy, the brain experiences rapid growth in the number of synaptic connections it has, peaking at approximately 15,000 at age 2-3 years (Gopnick et al. 1999). This equates to about twice as many 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. It was originally thought that such changes were restricted to the developing 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. However, more recent research suggests that at any time in life, existing neural connections can change, or new neural connections can be formed, as a result of learning and experience (plasticity).
What is the research into plasticity?
Eleanor Maguire et al. (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. It appears that the result of this learning experience is to alter the structure of the taxi drivers’ brains. It is also noteworthy that the longer they had been in the job the more pronounced the structural difference (a positive correlation).
A similar finding was observed by Draganski et al. (2006) who imaged the brains of medical students three months before and after their final exams. Learning-induced changes were seen to have occurred in the posterior hippocampus and the parietal cortex presumably as a result of the exam. Finally, Mechelli et al (2004) also found a larger parietal cortex in the brains of people who were bilingual compared to matched monolingual controls.
Explain the functional recovery of the brain after trauma?
Following physical injury or other forms of trauma such as the experience of 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 after trauma is another example of neural plasticity. 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 then slow 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?
The brain is able to rewire and reorganize itself by forming new synaptic connections close to the area of damage. Secondary neural pathways that would not typically be used to carry out certain functions are activated or ‘unmasked’ to enable functioning to continue, often in the same way as before (Doidge 2007). This process is supported by a number of structural changes in the brain including:
1) Axonal sprouting: The growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways.
2) Reformation of blood vessels.
3) Recruitment of homologous areas on the opposite side of the brain to perform specific tasks. An example would be if Broca’s area was damaged on the left side of the brain, the right-sided equivalent would carry out its functions. After a period of time, the functionality may then shift back to the left side.
A03: Brain plasticity
+ Practical application
- Potential negative consequences
- Individual differences
+ Support from animal studies
A03: Practical application
A strength of brain plasticity is its practical application. Understanding the process of recovery has contributed to neurorehabilitation. The techniques include movement therapy and electrical stimulation of the brain to treat cognitive problems experienced by a stroke. This shows that although the brain may be able to fix itself to a point, this process requires further intervention if it’s to be successful. Thus, it helps create interventions that can support recovery in those with brain processes.
A03: Support from animal studies
A strength is animal studies support it. Hubel and Wiesel sewed 1 eye of a kitten shut and analysed the response. The area of the visual cortex associated with the shut-eye was still working and carried out processing information in the open eye. This demonstrates how the loss of function leads to compensatory activity in the brain (evidence of neural plasticity.)
A03: Potential negative consequences
A limitation of neural plasticity is the potential negative consequences. The brain’s ability to rewrite itself can have maladaptive and negative behavioural consequences. 60-80% of amputees develop phantom limb syndrome: continued experience of sensations in the missing limb. Usually painful and thought to be due to reorganisation in the somatosensory cortex. This suggests structural and physical processes involved in functional recovery may not always be beneficial.
A03: Individual differences
While there is evidence for functional recovery, it is possible that this ability can deteriorate with age. Elbert et al. concluded that the capacity for neural reorganisation is much greater in children than in adults, meaning that neural regeneration is less effective in older brains. This may explain why adults find change more demanding than young people. Therefore, we must consider individual differences when assessing the likelihood of functional recovery in the brain after trauma.
A03: Functional recovery after trauma
+ Support from animal studies
+ Brain is affected by age
- Criticised for extrapolation
A03: Support from animal studies
There is research from animal studies to support the idea that the brain has the ability to recover after trauma. For example, Tajiri et al (2013) provided evidence for the role of stem cells in recovery from brain injury. They randomly assigned rats with traumatic brain injury to one of two groups. One group received transplants of stem cells into the region of the brain affected by the traumatic injury. The control group received a solution infused into the brain containing no stem cells. Three months later the brains of the stem cell rats showed clear development of neuron-like cells migrating into the brain’s site of injury. This was not the case with the control group. This is a strength because, in particular, this shows that with the help of stem cells, the brain is able to undergo functional recovery after injury.
A03: Brain is affected by age
There is research to suggest that functional recovery of the brain is affected by age. For example, Huttenlocher (2002) suggested that the only option following traumatic brain injury after childhood is to develop compensatory behavioural strategies to work around the deficit that older ages pose (such as seeking social support or developing strategies to deal with cognitive deficits). This is a strength because, Huttenlocher’s research confirms scientific and objective findings from research suggesting that with age, the brain’s ability the functional recovery declines.
A03: Criticised for extrapolation
However, this research can be criticised for extrapolation. For example, Tajiri et al (2013) research used a sample of rats. Rats and humans are physiologically different and it can be assumed that the effects of stem cells on the brains of rats may not be the same as the effects of stem cells on the brains of humans. This is a weakness because it means that research based on non-human animals cannot be generalised to humans and therefore it is difficult to draw firm conclusions.
