plasticity and functional recovery

plasticity

• refers to the fact that the brain can change and develop as a result of experience and learning, and it can recover after trauma and brain injury.

• the brain changes throughout the lifespan and during infancy, the brain experiences a rapid growth in the number of synaptic connections there are to other neurons.

• as we age, connections we don’t use are deleted and connections that we use a lot are strengthened - this process is synaptic pruning.

• even though the majority of changes in neural connections happen during childhood, adult brains still change and develop on a smaller scale, as a result of learning and experience.

Maguire et al (2000)

• studied the brains of London taxi drivers and found there was a significantly greater volume of grey matter in the posterior hippocampus (associated with spatial and navigational skills) than in a matched control group.

• part of a London taxi driver’s training involves taking a test known as ‘the knowledge’, which assesses their ability to recall the names and locations of the streets in the city.

• the results of the study suggest that the learning the drivers undertake as part of their training alters the structure of their brains.

• positive correlation between how big the volume of grey matter was and how long they had been in the job. (the longer the participant had been driving the taxi, the larger his hippocampus).

• evidence for structural differences in the brain due to extensive experience of spatial navigation.

• however it is correlational so we cannot necessarily conclude that the longer they worked as taxi drivers caused them to develop a larger posterior hippocampus - they could have chosen to be taxi drivers because they were already good at spatial awareness, therefore their hippocampus may have been naturally bigger.

Draganski et al (2006)

• 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 parietal cortex, presumably as a result of the exam.

Mechelli et al (2004)

found a larger parietal cortex in the brains of bilingual people, compared to non bilingual people.

functional recovery

• the brain is often able to recover from trauma that is caused by physical injury or illness.

• unaffected areas of the brain are often able to adapt and compensate for the areas that have been lost or damaged.

• this process can occur quickly after the trauma, but then slow down after several weeks or months.

• they may then require rehabilitative therapy to assist their recovery.

• the brain may reorganise and rewire itself by forming new synaptic connections close to the area of damage, and secondary neural pathways that would not usually be used to carry out certain functions are activated to enable functioning to continue, often in the same way as before.

axonal sprouting

• the growth of new nerve endings as neurons sprout new axon terminals.

• when a neuron is damaged, nearby neurons from pathways around the area of damage by growing new axonal pathways.

reformation of blood vessels

• where blood is redirected by vessels that grow larger to accommodate more oxygenated blood flow.

• new vessels that sprout to feed blood in and around an area of damage to aid recovery.

recruitment of homologous areas

• homologous areas on the other side of the brain can take over specific tasks.

• for example, if there has been damage to the right motor cortex causing struggle moving the left side of the body, the left motor cortex can take over and control movement in the left-hand side of the body instead of just the right side.

Danelli et al (2013) - case study of EB

• 17yr old boy who had his entire left brain hemisphere removed at 2yrs old due to non-cancerous tumour.

• by 5ys, his language fluency improved due to intensive rehabilitation, and by 17, using various brain scans, although there were minor problems with his grammar, in his everyday life, EB’s language appeared normal.

• suggests that language abilities can still function even after severe trauma, such as the removal of the left hemisphere.

• however, it is a case study so cannot necessarily be generalised to wider population - provides evidence but not proof.

• however, he was 2 when his left hemisphere was removed, and the younger you are the more likely it is you can recover from brain damage, so cannot be applied/generalised to adults suffering brain damage.