Plasticity and functional recovery of the brain after trauma Flashcards

1
Q

Define plasticity

A

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.

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2
Q

What is plasticity also known as?

A

neuroplasticity and cortical remapping

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3
Q

What did Gopnick et al find?

A

In infancy, the brain experiences growth in the number of synaptic connections it has, peaking at around 15,000 at age 2-3. This is twice as many as in the adult brain.

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4
Q

Define functional recovery

A

A form of plasticity. Following injury, unaffected areas of the brain are able to adapt and compensate for those areas that are damaged. As we age, rarely used connections are deleted and frequently used connections are strengthened in a process known as synaptic pruning.

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5
Q

What does synaptic pruning enable?

A

Enables lifelong plasticity where new neural connections are formed in response to new demands on the brain.

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6
Q

Give an example of plasticity in young humans

A

Sometimes a human baby is born with one extremely damaged hemisphere. If this hemisphere is removed at birth the baby has only one half of their brain… yet this results in few or no cognitive impairments.
Functions (e.g. language if the left hemisphere is removed) are transferred to the surviving brain areas. This is amazing evidence of plasticity.

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7
Q

What was originally thought about brain plasticity?

A

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.

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8
Q

However what does research suggest?

A

research suggests 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. Therefore brain plasticity continues into adulthood.

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9
Q

Who did research into plasticity?

A

Eleanor Maguire and Draganski et al

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10
Q

What did Maguire study?

A

studied the brains of London taxi drivers and compared them against a control group. This is because taxi drivers have to remember the map of London’s streets.

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11
Q

What did Maguire find?

A

found significantly more volume of grey matter in the posterior hippocampus in the taxi drivers than in a matched control group. Maguire et al. also found a positive correlation between the size of the posterior hippocampus and the time as a taxi driver = the longer they had been in the job, the more pronounced the structural difference was.

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12
Q

What is the posterior hippocampus associated with?

A

This part of the brain is associated with the development of spatial and navigational skills in humans and other animals. This difference shows plasticity.

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13
Q

Why did the taxi drivers have more grey matter in the posterior hippocampus?

A

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 (including all hotels, hospitals, etc). It appears that this spatial learning alters the structure of the taxi drivers’ brains.

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14
Q

What did Draganski et al do?

A

imaged the brains of medical students 3 months before and after their final exams.

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15
Q

What did Draganski et al find?

A

Learning-induced changes were seen to have occurred in the posterior hippocampus and the parietal cortex, presumably as a result of studying for exams (medical students need to learn an awful lot!)

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16
Q

Describe functional recovery

A

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

17
Q

When does functional recovery take place?

A

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.

18
Q

What causes brain trauma?

A

Physical trauma e.g. blows to head
Cerebral haemorrhage – when a blood vessel in the brain bursts the areas of the brain which depend on it start to die
Cerebral ischaemia – when a blood vessel in the brain is blocked (e.g. by a blood clot or arteriosclerosis) again blood does not get to brain areas
Infection e.g. meningitis

19
Q

What happens to the brain during recovery?

A

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 functioning to continue, often in the same ways as before (Doidge, 2007). This process involves other structural changes to the brain as well.

20
Q

Which structural changes in the brain support this process?

A

Axonal sprouting
Denervation supersensitivity
Neural regeneration / recruitment of homologous (similar) areas on the opposite side of the brain

21
Q

What is axonal sprouting?

A

New nerve endings grow and connect with undamaged nerve cells to form new neural pathways.

22
Q

What is denervation supersenstivity?

A

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.

23
Q

What is neural reorganisation?

A

Recruitment of similar areas on the opposite hemisphere to do those tasks.

24
Q

Give an example of neural reorganisation

A

if Broca’s area was damaged (remember, this is 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.

25
Q

Who did research into functional recovery?

A

Tajiri et al

26
Q

What did Tajiri et al do?

A

Provided evidence for the role of stem cells in producing functional recovery. 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 the traumatic injury. The control group received a solution containing no stem cells.

27
Q

What did Tarij find?

A

3 months after the brain injury the brains of stem cell rats showed clear development of neuron-like cells in the area of injury. The control group did not. This is strong evidence of functional recovery, as the stem cells produced new cells in the damaged area of the brain.