Plasticity and Functional Recovery Flashcards
Plasticity
- Brain plasticity: brain’s ability to change and adapt as result of experience
- As people gain new experiences, neural growth takes place + we develop neural pathways between neurons.
- Neural pathways that are frequently used develop stronger connections and those rarely used eventually die (axon pruning)
- By forming new and pruning old neural connections, our brain structure changes and allows our brain to constantly adapt to our experiences
- Plasticity is greatest in early life
Brain plasticity:
brain’s ability to change and adapt as result of experience
Axon pruning:
Neural pathways that are frequently used develop stronger connections and those rarely used eventually die
When is plasticity greatest?
in early life
Research into plasticity (summary of Maguire study):
- Maguire studied brains of London taxi drivers using structural MRI scans and found more volume of grey matter in the hippocampus than in a matched control group (non-taxi drivers)
- Taxi driver brains had more neurons in their grey matter as they must be able to recall many city streets and possible routes. Experiences can have impact on brain strcture
Functional recovery after trauma:
- FR represents transfer of function through neural reorganisation and rewiring from a damaged part of the brain to an undamaged part to regain some level of function.
Within this process the unharmed brain parts take over the lost function
Different ways of functional recovery after trauma:
- Neural reorganisation
- Neural regeneration
Neural reorganisation:
This is transferring the function from damaged areas to undamaged areas in order to recover function
Recruitment of homologous brain areas
When an area of the brain is damaged in one’s hemisphere (e.g. right motor cortex), similar areas in the opposite hemisphere (e.g. left motor cortex) physically changes and is used to take on the lost function.
Neural unmasking
- Wall identified ‘dormant synapses’ in the brain
- There are synaptic connections that exist anatomically but their function is blocked
- When a surrounding brain area becomes damaged, these dominant synapses can unmask - opening connections to regions of the brain that are not normally active -> leads to neural reorganisation + formation of new brain circuits which take on the function of damaged areas
Axon Sprouting (Neural regeneration)
After damage, the growth of new nerve endings which connect with other undamaged nerve cells + form new neural pathways and start restoring functioning
Four evals:
- Animal research supporting plasticity
- Case study supporting functional recovery
- Animal research supporting functional recovery
- Understanding of functional recovery is incomplete
A strength of plasticity research is supporting evidence from animal studies.
Evidence for the brain’s ability to change as a result of experience comes from animal studies.
Kermpermann et al investigated whether an enriched environment can alter the number of neurons in the brain. They found evidence of an increased number of new neurons in the brains of rats housed in complex environments compared to rats housed in lab cages. In particular, the rats housed in complex environments showed an increase in neurons in the hippocampus, a part of the brain associated with the formation of new memories. This shows that being exposed to complex experiences builds neural pathways + stronger connections between active neurons. This supports the idea that our brain does have plasticity and can change with experiences.
This validates our own understanding of the mechanisms of plasticity.
Case study supporting functional recovery:
Danelli et al assessed a 14 year old patient known as EB. EB was born with a tumour in their brain, and at the age of 2, underwent a left hemispherectomy. This removed important areas such as Broca’s area and Wernicke’s area, the two language centres. EB lost nearly all language capabilities after surgery. However, researchers found in the MRI images of EB’s brain, that the right hemisphere had adapted and changed structurally, to the point of ‘matching’ a similar structure that language centres lost in the left hemisphere would have had’.
Shows that brain reorganises after damage and loss of function. Other parts of the brain change structurally and take on the lost function- allowing for significant (but not always complete) recovery of functioning.
Therefore this validates mechanisms of functional recovery in humans.
Animal research supporting functional recovery:
Hubel and Weisel had sewn a cat’s eye shut in order to analyse its brain’s cortical responses. They found that the area of the visual cortex that processes information from the shut eye was not idle (as predicted) but continued to process information from the open eye.
While the visual cortex linked to the sewn eye should have stayed inactive in absence of sensory stimulation and input- it instead went through neural rewiring to take on the function of the intact eye.
Therefore it is plausible that when parts of the brain are damaged, the same mechanisms take place to restore function. Therefore adds validity to our understanding of functional recovery.
