plasticity & functional recovery of the brain after trauma

Question 1

what is plasticity?

Answer 1

This describes the brain’s tendency to change and adapt as a result of experience and new learning. This generally involves the growth of new connections.

Question 2

what happens during infancy?

Answer 2

During infancy, the brain experiences a rapid growth in the number of synaptic connections it has, peaking at about 15,000 per neuron at 2-3 years of age (Gopnik et al. 1999). This is about twice as many as there are in the adult brain.

Question 3

what happens when we age?

Answer 3

As we age, rarely-used connections are deleted and frequently-used connections are strengthened - a process known as synaptic pruning.
People once thought that the adult brain was not capable of change but we now understand that synaptic pruning enables lifelong plasticity where new neural connections are formed in response to new demands on the brain.

Question 4

what was Eleanor Maguire et al 2000’s research?

Answer 4

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 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.

Question 5

what did Maguire et al find?

Answer 5

found that this learning experience alters the structure of the taxi drivers’ brains. They also found that the longer the taxi drivers had been in the job, the more pronounced was the structural difference (a positive correlation).

Question 6

what was Bogdan Draganski et al 2006’s research?

Answer 6

he 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 the parietal cortex presumably as a result of the learning.

Question 7

what is the negative plasticity limitation?

Answer 7

-it may have negative behavioural consequences.
-Evidence has shown that the brain’s adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as an increased risk of dementia (Medina et al. 2007).
-Also, 60-80% of amputees have been known to develop phantom limb syndrome - the continued experience of sensations in the missing limb as if it were still there. These sensations are usually unpleasant, painful and are thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss (Ramachandran and Hirstein 1998).
-This suggests that the brain’s ability to adapt to damage is not always beneficial.

Question 8

what is the age & plasticity strength?

Answer 8

-brain plasticity may be a life-long ability.
-in general plasticity reduces with age, however, Ladina Bezzola et al. (2012) demonstrated how 40 hours of golf training produced changes in the neural representations of movement in participants aged 40-60.
-Using fMRI, the researchers observed increased motor cortex activity in the novice golfers compared to a control group, suggesting more efficient neural representations after training.
-This shows that neural plasticity can continue throughout the lifespan.

Question 9

what is the seasonal brain changes limitation?

Answer 9

-Research suggests that there may be seasonal plasticity in the brain in response to environmental changes.
-For example, consider the suprachiasmatic nucleus (SCN) which regulates the sleep/ wake cycle.
-There is evidence that this particular brain structure shrinks in all animals during spring and expands throughout autumn (Tramontin and Brenowitz 2000).
-However, much of the work on seasonal plasticity has been done on animals, most notably songbirds. Human behaviour may be controlled differently.

Question 10

what is functional recovery?

Answer 10

A form of plasticity. Following damage through trauma, the brain’s ability to redistribute or transfer functions usually performed by a damaged areas) to other, undamaged areas.

Question 11

what happens after brain trauma?

Answer 11

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 an example of neural plasticity.
Healthy brain areas may take over the functions of those areas that are damaged, destroyed or even missing.

Question 12

is functional recovery fast or slow?

Answer 12

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 rehabilitative therapy to further their recovery.

Question 13

what happens in the brain during recovery?

Answer 13

The brain is able to rewire and reorganise itself by forming new synaptic connections dose to the area of damage. Secondary neural pathways that would not typically be used to carry out certain functions
are activated or ‘unmasked’ to enable functioning to continue, often in the same way as before (Dodge 2007).

Question 14

what are 3 structural changes in the brain?

Answer 14

axonal sprouting,
denervation super sensitivity,
recruitment of homologous (similar) a reason the opposite side of the brain

Question 15

what is axonal sprouting?

Answer 15

the growth of new nerve endings which connect with other undamaged
nerve cells to form new neuronal pathways.

Question 16

what is denervation supersensitivty?

Answer 16

this occurs when axons that do a similar job become aroused to a higher level to compensate for the ones that are lost. However, it can have the negative
consequence of oversensitivity to messages such as pain.

Question 17

what is recruitment of homologous (similar) a reason the opposite side of the brain?

Answer 17

This means that specific tasks can still be performed. An example would be if Brocas 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.

Question 18

what is the real-world application strength?

Answer 18

-the research has real-world application.
-Understanding the processes involved in plasticity has contributed to the field of neurorehabilitation. Simply understanding that axonal growth is possible encourages new therapies to be tried.
-For example constraint-induced movement therapy is used with stroke patients whereby they repeatedly practise using the affected part of their body (such as an arm) while the unaffected arm is restrained.
-This shows that research into functional recovery is useful as it helps medical professionals know when interventions need to be made.

Question 19

what is the cognitive reserve limitation?

Answer 19

-the level of education may influence recovery rates.
-Eric Schneider et al. (2014) revealed that the more time people with a brain injury had spent in education - taken as an indication of their ‘cognitive reserve - the greater their chances of a disability-free recovery (DFR).
-40% of those who achieved DFR had more than 16 years’ education compared to about 10% of those who had less than 12 years’ education.
-This would imply that people with brain damage who have insufficient DR are less likely to achieve a full recovery.

Question 20

what is the small sample limitation?

Answer 20

-Research is ongoing for new treatments to aid functional recovery.
-For instance, a study by Soma Banerjee et al. (2014) treated people who had a total anterior circulation stoke (TACS) with stem cells. All participants in this trial recovered compared to the more typical level of just 4% recovery.
-However this study drew conclusions based on just five participants and no control group, which is fairly typical of research on functional recovery.