plasticity of the brain Flashcards
what does plasticity mean with regards to the brain?
it means that the brain can change and adapt over time as a result of experience and new learning
how was the view of plasticity changed?
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.
Research has since demonstrated that the brain continues to create new neural pathways and alter existing ones in response to changing experiences.
how does infant development demonstrate plasticity?
During infancy the brain experiences growth in the number of synaptic connections it has; peaking at around 15,000 per neuron at age 2-3 (Gopnick et al. 1999).
how does infant plasticity relate to the adult brain?
This is twice as many connections per neuron as in the adult brain.
As we age, connections that are rarely used are deleted and frequently used connections are strengthened in a process known as synaptic pruning.
what is functional recovery?
A form of plasticity where following damage from trauma the brain is able to redistribute functions normally performed by damaged areas to other undamaged areas
Give 4 examples of how when environments are enriched or impoverished, it is reflected in brain
plasticity
- Romanian orphans suffered conditions of neglect and understimulation. PET scans of their brains show hypometabolism in the temporal lobes, indicating lack of neural development.
- Davidson et al (2004) found that Tiebetan monks had increased gamma waves (coordinate neuronal activity) when meditating. This showing long term changes
- Rosenweig et al (1972) brains of the enriched rats were different from the impoverished rats; the neurons were larger, the cerebral cortex heavier and thicker.
- Boyke et al (2008) – there is a natural decline in cognitive functioning with age. Boyke found that 60year olds had increased grey matter in the visual cortex when learning to juggle. It decreased when they stopped
explain Maguire’s 2000 study
Aim: the posterior hippocampus is associated with spatial and navigational skills. Maguire was interested in whether participants with extensive experience in the use of navigational skills would show increased brain volume in this region.
Method: 16 male right-handed taxi drivers were compared to 50 healthy right-handed males who were not taxi drivers. The taxi drivers have to undergo extensive navigational training, known as ‘The Knowledge’ in order to become a licensed taxi driver. Using MRI, the volume of the hippocampus was compared between groups
Results: taxi drivers showed an increase in volume of the posterior hippocampus, compared to healthy volunteers, and smaller anterior hippocampus
why is a straightforward interpretation of these findings complicated?
The results are correlational, so the association could be spurious: correlation is not causation, and can be the simple result of chance.
what might be an alternative explanation to correlation not causes causation?
It is possible the causality could be in the opposite direction: that is, those with strong navigational skills, and therefore have a larger posterior hippocampus, are more likely to seek employment in positions which utilise these skills, such as taxi driving.
what does research imply about the results of maguires results
The positive correlation between posterior hippocampal volume and duration of taxi driving implies that the experiential difference between the two groups may represent neuroplasticity, with experience and learning resulting in an increase in regional brain volume in areas associated with the relevant function.
name two other studies that are consistent with the findings of Maguire
Draganski et al. (2006) imaged the brains of medical students 3 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 studying for exams
- Mechelli et al. (2004) found a larger parietal cortex in the brains of people who were bilingual compared to matched monolingual controls.
how does functional recovery suggest plasticity?
Following physical injury or trauma such as stroke, unaffected areas of the brain are often able to adapt and compensate for those areas that are damaged.
Recovery is more likely at a younger age, where the potential for plasticity is greater.
The functional recovery that may occur in the brain after trauma is another example of neural plasticity
how does neural reorganisation support plasticity?
Healthy brain areas may take over the functions of those areas that are damaged, destroyed or even missing (neural reorganisation).
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 need rehabilitative therapy
how can neural reorganisation occur?
Through the recruitment of homologous areas when a homologous (similar) area of the brain on the opposite side is used to perform a specific task, for example the case of JW that developed language in the right hemisphere, where the homologous area in the right hemisphere of Broca’s area in the left hemisphere, may take over its role in speech production
what is neurogenesis?
The brain is able to rewire and reorganise itself by forming new neurons (neurogenesis) and/or synaptic connections close to the area of damage
