Plasticity & Functional Recovery of Brain after Trauma

Question 1

Define Plasticity.

Answer 1

The brain’s tendency to change and adapt (functionally and physically) as a result of experience and new learning.

Question 2

Define Functional Recovery.

Answer 2

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

Question 3

Brain Plasticity.

Answer 3

The ability of the brain to change throughout life.

Question 4

What happens during infancy?

Answer 4

The brain experiences rapid growth in the number of synaptic connections it has, peaking at approximately 15000 at age 2-3 years (Gopnick et al 1999).

Question 5

What differs between an adult and an infant’s brain?

Answer 5

An infant has twice as many synaptic connections compared to an adult.

Question 6

Define synaptic pruning.

Answer 6

The process where as we age, rarely used connections are deleted and frequently used connections are strengthened.

Question 7

What was originally thought of plasticity?

Answer 7

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.

Question 8

What does recent research into plasticity suggest?

Answer 8

That at any time in life existing neural connections can change, or new neural connections can be formed, as a result of learning and experience.

Question 9

Eleanor Maguire et al 2000 studied…

Answer 9

the brains of London taxi drivers.

Question 10

Maguire et al 2000 - what was expected of the participants?

Answer 10

As part of training, London cabbies take a complex test - The Knowledge - assessing their recall of city streets and possible routes. Maguire et al tried to find differences in the structure of their brains compared to normal people.

Question 11

Maguire et al 2000 - findings.

Answer 11

The taxi drivers’ brains had an alteration in their brain structure.
Found significantly more volume of grey matter in the posterior hippocampus than in a matched control group - part of brain linked with the development of spatial and navigational skills in humans and other animals.
The longer they had been in the job, the more pronounced was the structural difference - positive correlation.

Question 12

Draganski et al 2006 observed…

Answer 12

brain images of medical students 3 months before and after their final exams.

Question 13

Draganski et al 2006 found that…

Answer 13

learning-induced changes were seen to have occurred in the posterior hippocampus and the parietal cortex presumably as a result of the exam.

Question 14

Mechelli et al 2004 found that…

Answer 14

a larger parietal cortex in the brains of people who were bilingual compared to matched monolingual controls.

Question 15

What happens after following physical injury or other forms of trauma?

Answer 15

Unaffected areas of the brain are often able to adapt and compensate for those areas that are damaged.
Healthy brain areas may take over the functions of those areas that are damaged, destroyed, or even missing,

Question 16

Neuroscientists suggest that functional recovery…

Answer 16

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 17

What happens in the brain during recovery?

Answer 17

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 activated or ‘unmasked’ to enable the functioning to continue, often in the same way as before (Doidge 2007).

Question 18

Functional recovery is supported by a number of structural changes in the brain including:

Answer 18

Axonal sprouting - the growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways.
Reformation of blood vessels.
Recruitment of homologous (similar) areas on the opposite side of the brain to perform specific tasks.

Question 19

Strength - practical application

Answer 19

Understanding the processes involved in plasticity has contributed to the field of neurorehabilitation.
Following illness or injury to the brain, spontaneous recovery tends to slow down after a number of weeks so forms of physical therapy may be required to maintain therapy and electrical stimulation of the brain to counter the deficits in motor and/or cognitive functioning that may be experienced following an injury/illness.
This shows that, although the brain may have the capacity to ‘fix itself’ to a point, this process requires further intervention if it is to be completely successful.

Question 20

Weakness - negative plasticity

Answer 20

The brain’s ability to rewire itself can sometimes have maladaptive behavioural consequences. Prolonged drug use has been shown to result in poorer cognitive functioning as well as an increased risk of dementia later in life (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).

Question 21

Strength - age and plasticity

Answer 21

Functional plasticity tends to reduce with age. The brain has greater prosperity for reorganisation in childhood as it is constantly adapting to new experiences and learning.
That said, Ladina Bezzola et al (2012) demonstrated how 40 hours of golf training produced changes in the neural representation of movement in participants aged 40 - 60. Using fMRI, the researchers observed reduced motor cortex activity in the novice golfers compared to a control group, suggesting more efficient neural representations after training. This shows that neural plasticity does continue throughout the lifespan.

Question 22

Strength - support from animal studies

Answer 22

Early evidence of neuroplasticity and functional recovery was derived from animal studies.
A pioneering study by David Hubel and Torsten Wiesel (1963) involved sewing one eye of a kitten shut and analysing the brain’s cortical responses. It was found that the area of the visual cortex linked with the shut eye wasn’t idle (as predicted) but continued to process information from the open eye.

Question 23

Strength - the concept of cognitive reserve

Answer 23

Evidence suggests that a person’s educational attainment may influence how well the brain functionally adapts after injury. Eric Schneider et al (2014) discovered that the more time brain injury patients had spent in education - which was taken as an indication of their ‘cognitive reserve’ - the greater their chances of a disability-free recovery (DFR). Two-fifths of patients studied who achieved DFR had more than 16 years’ education compared to about 10% of patients who has less than 12 years’ education.