Bio - Plasticity & functional recovery of the brain Flashcards

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1
Q

What is brain plasticity?

A

Refers to the brain’s ability to modify its own structure and function as a result of experience.

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2
Q

What is functional recovery?

A

Refers to the recovery of abilities and mental processes that have been compromised as a result of brain injury or disease.

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3
Q

What are some factors that are known to affect neuronal structure and function?

A

Life experience, video games and meditation.

Life experiences could include; learning new skills, a result of developmental changes, response to direct trauma to an area/areas of the brain, response to indirect effects of damage such as brain swelling or bleeding (from stroke).

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4
Q

How does life experience affect plasticity?

A

As people gain new experiences, nerve pathways that are frequently used develop stronger connections, whereas neurons that are rarely used eventually die. By developing new connections and pruning away weak ones, the brain is able to constantly adapt to the changing environment.

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5
Q

By developing new connections and pruning away weak ones, what is the brain able to do?

A

Constantly adapt to the changing environment.

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6
Q

What changes to do with age can be attributed to the brain?

A

There is a natural decline in cognitive functioning.

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7
Q

What research has been done into plasticity in older ages?

A

Researchers are looking for ways in which new connections can be made to reverse the effect of age.

For example, Boyke et al. (2008) found evidence of brain plasticity in 60 year olds taught a new skill - juggling. They found increases in grey matter in the visual cortex, although when practising stopped, these changes were reversed.

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8
Q

How does playing video games affect plasticity?

A

Playing video games makes many different complex cognitive and motor demands and so as a result the researchers concluded that video game training had resulted in new synaptic connections in brain area involved in spatial navigation, strategic planning, working memory and motor performance - skills that were important in playing the game successfully.

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9
Q

What evidence is there for the fact that playing video games has an effect on plasticity?

A

Kuhn et al. (2014) compared a control group with a video game training group that was trained for two months for at least 30 mins per day on the game Super Mario.

They found a significant increase in grey matter in various brain areas including the cortex, hippocampus and cerebellum. This increase was not evident in the control group that did not play Super Mario.

The researchers concluded that video game training had resulted in new synaptic connections in brain area involved in spatial navigation, strategic planning, working memory and motor performance - skills that were important in playing the game successfully.

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10
Q

How does meditation affect plasticity?

A

Meditation not only changes the workings of the brain in the short term, but may also produce permanent changes, based on the fact that far more gamma wave activity was found in those who meditated than those who didn’t.

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11
Q

What evidence is there for the fact that meditation has an effect on plasticity?

A

Researchers working with Tibetan monks have been able to demonstrate that meditation can change the inner workings of the brain. Davidson et al. (2004) compared eight 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. The electrodes picked up much greater activation of gamma wave activity while meditating.

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 fact that the monks had far more gamma wave activity than the control group even before they started meditating.

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12
Q

What are the mechanisms for recovery?

A

Neuronal unmasking and stem cells.

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13
Q

Who discovered neuronal unmasking and how?

A

Wall (1977) first identified what he called ‘dormant synapses’ in the brain. These are synaptic connections that exist anatomically but their function is blocked.

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14
Q

Describe neuronal unmasking as a mechanism for recovery

A

Wall (1977) first identified what he called ‘dormant synapses’ in the brain. These are synaptic connections that exist anatomically but their function is blocked.

Under normal conditions these synapses may be ineffective because the rate of neural input to them is too low for them to be activated. However, increasing the rate of input to these synapses, as would happen when a surrounding brain area becomes damaged, can then open (or ‘unmask’) these dormant synapses.

The unmasking of dormant synapses can open connections to regions of the brain that are not normally activated, creating a lateral spread of activation which, in time, gives way to the development of new structures.

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15
Q

What are stem cells?

A

Specialised cells that have the potential to give rise to different cell types that carry out different functions, including taking on characteristics of nerve cells.

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16
Q

How are stem cells a mechanism for recovery?

A

They have the potential to give rise to different cell types that carry out different functions, including taking on characteristics of nerve cells.

They might work to provide treatments for brain damage caused by injury of neurodegenerative disorders by:

  • Being implanted into the brain to directly replace dead or dying cells.
  • Being transplanted to secrete growth factors that somehow ‘rescue’ the injured cells.
  • Being transplanted so they form a neural network, which links an uninjured brain site, where new stem cells are made, with the damaged region of the brain.
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17
Q

How did the views of functional recovery come about?

A

In the 1960’s researchers studied cases in which stroke victims were able to regain functioning.

They discovered that when brain cells are damaged or destroyed, as they are during a stroke, the brain re-wires itself over time so that some level of function can be regained.

Although parts of the brain may be damaged or even destroyed as a result of trauma, other parts appear able to take over the functions that were lost. Neurons next to damaged brain areas can form new circuits that resume some of the lost function.

18
Q

What is synaptic pruning?

A

When synapses that are frequently used become stronger over time and the unused synaptic connections are lost. This makes the brain a more efficient communication system over time.

19
Q

Why is synaptic pruning a good thing for the brain?

A

Because it means that the brain becomes a more efficient communication system over time.

20
Q

What is denervation supersensitivity?

A

To compensate for the loss of axons in a pathway, the remaining axons become more sensitive (more likely to fire). This can result in side effects, e.g. pain.

21
Q

What are factors affecting functional recovery?

A

Age, gender and rehabilitative therapy.

22
Q

How does age affect functional recovery?

A

Children have the best ability to recover, then young adults.

23
Q

How does gender affect functional recovery?

A

Women are more able to recover from brain damage.

24
Q

How does rehabilitative therapy affect functional recovery?

A

Focused effort results in improvement.

25
Q

What is constraint induced therapy?

A

Stopping patients using coping strategies (e.g. body language for communication or using undamaged limbs for tasks) makes them improve via functional reorganisation.

26
Q

What is the key study on functional recovery?

A

Maguire et al. (2000)

27
Q

What was the aim of the study done by Maguire et al. (2000) on functional recovery?

A

To examine whether structural changes could be detected in the brains of people with extensive experience of spatial navigation.

28
Q

What was the independent variable/method of the study done by Maguire et al. (2000) on functional recovery?

A

Structural MRI’s of 16 right handed male London Taxi drivers who’d been driving for more than 1.5 years and scans of 50 healthy right handed males who did not drive taxis for comparison.

29
Q

What were the results of the study done by Maguire et al. (2000) on functional recovery?

A

1) Increased grey matter was found in the brains of taxi drivers compared with controls in the two brain regions, the right and left hippocampus. The increased volume was found in the posterior hippocampus.
2) Changes with navigation experience - a positive correlation was found between the amount of time spent as a taxi driver and the volume in the right posterior hippocampus.

30
Q

What was the conclusion of the study done by Maguire et al. (2000) on functional recovery?

A

Supports the idea of brain plasticity and suggests that experience (driving a taxi) can change the structure of the brain (enlarged hippocampus).

31
Q

What is a stroke?

A

Sudden death of brain cells due to a lack of oxygen to them.

32
Q

What is traumatic brain injury?

A

A blow to the head that disrupts normal brain functioning.

33
Q

What is axonal sprouting?

A

A process where nerve processed grow out from the intact axons to reinnervate denervated muscle fibres.

34
Q

What is motor learning?

A

When complex processes in the brain occur in response to practice or experience of a certain skill resulting in change.

35
Q

Apart from Maguire et al. (2000) give other evidence for functional recovery

A

Danelli et al. (2013)

  • 14 year old EB had a brain tumour removed aged 2 and a half, on the left side of his brain - removed language centres of Broca’s and Wernicke’s areas.
  • He lost all language ability (aphasia), however EB had recovered this after 2 years.
  • Researchers did an fMRI scan and found a left-like blueprint in the right hemisphere.
  • Suggests the brain can adapt and recover after significant damage; especially in early life, with the right hemisphere taking roles usually performed by the left.
36
Q

What is structural plasticity?

A

(Growth) - experience causes a change to brain structure.

37
Q

What is another name for functional recovery?

A

Functional plasticity.

38
Q

What is functional plasticity?

A

(Recovery) - localised functions move from a damaged region to an undamaged region after injury.

39
Q

Describe the process of growth and change in the brain (structural neuroplasticity)

A

Stage 1 = synaptic pruning:
- Axons that aren’t used will weaken and eventually be lost.

Stage 2 = neural unmasking:
- A hormone; nerve growth factor (NGF) encourages growth.

Stage 3 = axonal sprouting:
- Chemicals called neurotrophins sustain and encourage growth.

Stage 4 = synaptic connection:
- The new connection makes its parent network stronger.

40
Q

Describe the process of functional recovery in the brain (structural neuroplasticity)

A

Stage 1 = axon damage (axotomy):
- Axon is severed by injury (dendrites would just re-grow).

Stage 2 = axonal sprouting:
- New axon/dendrite growth towards target.

Stage 3 = blood vessels re-form (capillaries and glial cells):
- ‘Glial’ cells wrap around capillaries; supporting the blood-brain barrier.

Stage 4 = recruitment of homologous (similar) areas:
- Usually on the opposite hemisphere.