Plasticity and functional recovery of the brain after trauma

Question 1

What is plasticity?

Answer 1

The brain’s tendency to change and adapt as a result of experience and new learning

Question 2

How plastic is the brain during infancy?

Answer 2

• The brain experiences a rapid growth in the number of synaptic connections
• 15,000 per neuron at 2-3 years (Gopnik)

Question 3

How many synaptic connections are there in the adult brain?

Answer 3

2x the amount in a 2-3 year olds brain (around 30,000)

Question 4

What happens to rarely and frequently used connections?

Answer 4

• Rarely-used connections are deleted
• Frequently-used connections are strengthened (synaptic pruning)

Question 5

What does synaptic pruning do?

Answer 5

Enables lifelong plasticity, where new neural connections form in response to demands from the brain

Question 6

What did Maguire study?

Answer 6

Brains of London taxi drivers

Question 7

What did Maguire find?

Answer 7

• London taxi drivers have significantly more volume of grey matter in the posterior hippocampus than a control group (associated with navigational and spatial skills)
• Completing the ‘Knowledge test’ alters brain structures (longer doing the job, more pronounced the structural difference)

Question 8

What did Draganski et al study and find?

Answer 8

• Imaged brains of medical students 3 months before and after their final exams
• Found learning induced changes occured in the posterior hippocampus and parietal cortex

Question 9

Strength:
I- Lifelong plasticity

Plasticity

Answer 9

D- Bezzola et al showed how 40 hours of golf training produced changes in neural representations of movement in participants aged 40-60 years. USed fMRI to observe increased motor cortex activity in novice golfers vs control
E- Shows that neural plasticity can continue throughout the lifespan

Question 10

Limitation:
I- Negative plasticity

Plasticity

Answer 10

D- Medina- the brain’s adaptation to prolonged drug use leads to poorer cognitive functioning later in life and a risk of dementia. Ramachandran and Histrein- 60-80% of amputees develop phantom limb syndrome (continued experience of sensations due to cortical reorganisation in the somatosensory cortex)
E- Suggests the brain’s ability to adapt to damage may not be beneficial

Question 11

Evaluation extra:
I- Seasonal brain changes

Plasticity

Answer 11

Strength: Seasonal plasticity occurs due to enviornmental changes. Tramontin and Brenowitz- suprachiasmatic nucleus regulating the sleep/wake cycle shrinks in animals during spring and expands in autumn

Limitation: Seasonal plasticity work carried out on animals. Similar biological mechanisms exist across species but human and bird pacemakers differ. Human behaviour is under conscious control and there is less adaptive pressure to develop biological mechanisms to fit enviornments

Question 12

What is functional recovery?

Answer 12

A form of plasticity, following damage through trauma: the brain’s ability to redistribute/ transfer functions

Question 13

What happens to the brain after physical injury or trauma?

Answer 13

• Unaffected brain areas adapt and compensate for damaged areas
• Healthy brain areas may take over the functions of damaged, destroyed or missing areas (occurs quickly after trauma and slows down after several weeks/months

Question 14

What happens in the brain during recovery?

Answer 14

• The brain rewires and reorganises itself by forming new synaptic connections close to the damaged area
• Doidge-secondary neural pathways are activated to enable functioning to continue
• Supported by 3 structural changes: axonal sprouting, denervation supersensitivity, recruitment of homologous areas

Question 15

What is axonal sprouting?

Answer 15

The growth of new nerve endings that connect with other undamaged nerve cells to form new neural pathways

Question 16

What is denervation supersensitivity?

Answer 16

Occurs when axons become aroused to a higher level to compensate for lost axons. It can have a negative consequence of oversensitivity to messages (pain)

Question 17

What is recruitment of homologous areas (on the opposite side of the brain)?

Answer 17

Means specific tasks can be formed. E.g: if Broca’s areas were damaged on the left side of the brain, the right sided equivalent would carry out its functions

Question 18

Strength:
I- Real world application

Functional recovery

Answer 18

D- Understanding processes involved in plasticity contribute to the field of neurorehabilitation. Understanding axonal growth encourages new therapies to be tried. E.g: constraint-induced movement therapy is used with stroke patients- they repeatedly practice using the affected part of their body, while the unaffected area is restrained
E- Shows usefulness of research in helping medical professionals to know when interventions should be made

Question 19

Limitation:
I- Cognitive reserve

Functional recovery

Answer 19

D- Levels of eductaion may influence recovery rates. Schnieder et al found more time people with brain injuries spent in education (cognitive reserve), greater their chances of a disability free recovery (DFR). 40% of those who achieved DFR had 16+ years of eductaion vs 10% of those with less than 12 years
E- Implies people with brain damage who have insufficent DFR are less likely to achieve a full recovery

Question 20

Evaluation extra:
Small samples

Functional recovery

Answer 20

Strength: Banerjee et al treated patients with total anterior circulation stroke (TACS) with stem cells. All patients recovered vs 4% recovery at typical level. Dataa provides support for use of stem cells in helping functional recovery

Limitation: Conclusions based on 5 patients. Small samples mean conclusions may not be generalisable. No control group and research lacks validity so hard to draw conclusions