- Created by: abbie0107
- Created on: 13-08-19 21:26
Plasticity is when the brain changes and adapts (functionally and physically), as a result of experience and new learning.
During infancy, the brain experiences a rapid growth in the number of synaptic connections it has, peaking at approximately 15,000 at age 2-3 years.
As we age, rarely used connections gets deleted and frequently used connections are strengthened - a process known as synaptic pruning.
Most 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.
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.As part of their traning, London cabbies must take a complex test 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. The longer they had been on the job, the more pronounced was the structural difference.
Draganski et al (2006) who imaged the brains of medical students three months before their final exams. Learning-induced changes were seen to have occured in the posterior hippocampus and the parietal cortex presumably as a result of the exam.
Mechelli et al (2004) also found a larger parietal cortex in the brains of people who were bilingual compared to matched monolingual controls.
High ecological validity and high mundane realism but low population validity it is also reliable as it is observable and high internal validity /Growth mind-set from Dweck that with mindful practice skills develop so the brain changes /The brain is more plastic and an early age
Functional Recovery of the Brain
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 therapy to further their recovery.
What happens during recovery?
The brain is able to rewire and reorganise 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 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:
- Axonal sprouting: the growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways.
- Reformation of blood vessels.
- 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, functionality may then shift back to the left side.
Practical application: Understanding the processes involved in plasticity has contributed to the field of neurorehabilitation. Spontaneous recovery tends to slow down after a number of weeks so forms of physical therapy may be required to maintain improvements in functioning. This shows that, although the brain may have the capacity to 'fix itself' to a point, this process requires further intervention if it is to be completely successful.
Negative plasticity: The brain's ability to rewire itself can sometimes have maladaptive behavioural consequences. Prolonged drug use has been shwon to result in poorer cognitive functioning as well as an increased risk of dementia later in life (Medina et al 2007). 60-80% of amputees have been known to develop phantom limb syndrome. This is thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss (Ramachandran and Hirstein 1998).
Age and Plasticity: Functional plasticity tends to reduce with age. The brain has a greater propensity for reorganisation in childhood as it is constantly adapting to new experiences and learning. Ladina Bezzola et al (2012) demonstrated how 40 hours of golf traning produced changes in the neural representation of movement in participants aged 40-60. Neural plasticiy does continue throughout the lfiespan.
Support from animal studies: Early evidence of neuroplasticity and functional recovery was derived from animal studies. A study by David Hubel and Torten Wiesel (1963) involved sewing one eye of a kitten shut and analysing the brain's cortical responses. The shut eye continued to process information from the open eye.
The concept of cognitive reserve: Eric Schneider et al (2014) discovered that the more time a brain injury patient spend in education, the greater their chances of a disability-free recovery. Two-fifths of patients studied who achieved DFR had more than 16 years education compared to 10% who had less than 12 years education.