Plasticity and functional recovery Flashcards
define plasticity
plasticity, also known as neuroplasticity or cortical remapping, describes the brains tendency to change and adapt (functionally and physically) as a result of experience and new learning.
Describe the brain in childhood and infancy
During infancy, the brain experiences a rapid growth in the number of synaptic connections it has, peaking at approximately 15,000 by the age of 2-3 years old. This equates to twice as many as there are in the adult brain.
Describe cognitive pruning
As we age, rarely used connections are deleted and frequently used connections are strengthened in a process known as cognitive pruning
This shows that the brain is in a continual state of change from growth in early years to change and refinement in adulthood as we learn and experience.
Explain how plasticity can be negative using examples
Examples of this would include prolonged (illegal) drug use leading to poorer cognitive function and old age being associated with dementia. Both are due to changes in the brain.
List 2 studies for plasticity
- Macguire et al 2000
- Tibetan monks
Outline Macguire et al 2000
Macguire et al studied the brains of London taxi drivers using an MRI and found significantly more grey matter in the posterior hippocampus than in the 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.
What were the findings of Macguire et al 2000
the longer they had been doing the job the more pronounced was the structural difference (a positive correlation).
What are the strengths of Macguire et al 2000
S – matched control group – can say with more certainty that it is due to their driving rather than extraneous variables.
S – scientific – objective measurements - MRI – more accurate
what are weaknesses of Macguire et al 2000
W – sample – only from London, only taxi drivers – cant generalise to other jobs
W – they were not tested before they underwent the training
Outline the Tibetan monks study
- 8 practitioners of Tibetan meditation with 10 student volunteers with no previous meditation experience.
- Both groups were fitted with electrical sensors and asked to meditate for short periods.
What were the findings of the Tibetian monks study
The electrodes picked up on much greater activity of gamma waves (important because they coordinate neuron activity) in the monks. While the students showed only a slight increase in gamma wave activity while meditating.
Give a conclusion for the Tibetian monks study
The researchers concluded that meditation not only changes the workings of the brain in the short term, but may also produce permanent changes, based on the facts that the monks had far more gamma wave activity than the control group even before they started meditating.
evaluate the Tibetian monks study
S - used electrodes - scientific - increase accuracy
W - small sample size with inexperience from the students - may have struggled - squewed the sample
What is the connection between plasticity and age
There is also a natural decline in cognitive functioning with age that can be attributed to changes in the brain.
This has led researchers to look for ways in which new connections can be made to reverse this effect.
Give a piece of research into plasticity and age.
Boyke et al (2008) found evidence of brain plasticity in 60 yr. olds taught a new skill – juggling. They found increases in grey matter in the visual cortex, although when practicing stopped, these changes reversed.
define functional recovery
Functional recovery is a form of plasticity. Following trauma (such as infection or physical injury) unaffected areas of the brain are sometimes able to adapt or compensate for those areas that are damaged. The functional recovery that occurs in these cases is an example of neural plasticity
define spontaneous recovery
is the term used to refer to functional recovery that happens very quickly after a trauma.
Explain what happens to the brain 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 ‘unmasked’ to enable functioning to continue. This process is supported by a number of structural changes.
List the structural changes that happen during functional recovery
- Axon sprouting
- reformation
- recruitment of homologous areas
define/ explain axon sprouting
new nerve endings grow and connect with undamaged areas.
define/ explain reformation in functional recovery
the reforming of blood vessels
define/ explain recruitment of homologous areas for functional recovery
the brain recruits similar areas on the opposite hemisphere to do specific tasks
e.g. if Broca’s area was damaged then an area on the right might take over
Give example(s) research into functional recovery
- Tajiri et al 2013
- Schneider et al 2014
outline Tajiri et al 2013
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 2 groups. One group received transplants of stem cells into the region of the brain affected by traumatic injury. The control group received a solution infused into the brain containing no stem cells.
What were the findings of Tajiri et al 2013
Three months after the brain injury, the brains of stem cell rats showed clear development of neuron-like cells in the area of injury. This was accompanied by a solid stream of stem cells migrating to the brain’s site of injury. This was not the case with the control group.
Evaluate Tajiri et al 2013
1S, 1W
W – animal studies are hard to generalise to humans
S - Animal studies enable us to monitor the function of the brain before and after trauma because we cause it. Ethically we couldn’t do this in humans and it’s unlikely that we would have measured their function before a natural event (because we didn’t know it was going to happen).
Outline Schneider et al 2014
Schneider et al (2014) found that patients with the equivalent of a college education are seven times more likely than those who didn’t finish high school to be disability-free one year after a moderate to severe traumatic brain injury. They carried out a retrospective study based on data from the US Traumatic Brain Injury Systems Database.
Describe the findings of Schneider et al 2014
Of the 769 patients studied (large sample), 214 had achieved disability-free recovery (DFR) after one year. Of these, 39.2% of the patients with 16 or more years of education had achieved DFR, as had 30.8% of those with 12-15 years of education, and just 9.7% of those with less than 12 years of education achieved DFR after just one year.
DFR - disability free recovery
Give a conclusion for Schneider et al 2014
The researchers concluded that ‘cognitive reserve’ (associated with greater educational attainment) could be a factor in neural adaptation during recovery from traumatic brain injury.
Give a strength of Schneider et al 2014
S - large sample size
Fully outline Lashley 1950
including results
experiment on rats where he removed 10-50% of their cortex to see if it effected the rat’s ability to learn a route through a maze. In his experiment he found that no area was proven to be more important than any other when it came to learning the route, in fact the process of learning seemed to use every part of the cortex rather than a specific area. This suggests that higher cognitive processes (e.g. learning) are not localised in the brain of rats but distributed in a holistic way.
Evaluate Lashley
A weakness of Lashley 1950 though is that he used rats, this is a weakness because he is trying to apply to humans, and it is hard generalise from rats to humans. This means that Lashley’s 1950 experiment can only be applied to rats and suggested for humans.
