Plasticity and Functional Recovery of the Brain After Trauma

Question 1

Define what it is meant by Plasticity

Answer 1

• Refers to the brain’s ability to change and adapt because of experience.
• Experience includes everything outside the body (e.g. driving a car, playing a musical instrument etc.), and the functions and processes of the brain can change as a result of these experiences

Question 2

Recap Neural Pathways

Answer 2

• When you take in information for the first time, a new neural pathway is created in the brain creating a memory trace.
• To begin with, this neural pathway is very fragile (easily decay-able) because the information is new.
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• But repetition and consolidation strengthens this pathway, making it more memorable each time.

Question 3

Example of Plasticity

Answer 3

• During infancy, the brain experiences a rapid growth in the number of synaptic connections it has, peaking at approximately 15,000 by the age of 2-3 years old.
• This equates to twice as many as there are in the adult brain. As we age rarely used connections are deleted and frequently used connections are strengthened.
• This shows that the brain is in a continual state of change from growth in early years to change and refinement in adulthood as we learn and experience.

Question 4

What is Functional Recovery?

Answer 4

• A type of Plasticity
• The transfer of functions from a damaged area of the brain after trauma to other undamaged areas
• It can do this through a process termed neuronal unmasking where ‘dormant’ synapses (which have not received enough input to be active) open connections to compensate for a nearby damaged area of the brain.

Question 5

What is Neuronal Unmasking?

Answer 5

• This is where dormant synapses (which have not received enough input to be active) open connections to compensate for a nearby damaged area of the brain.
• The dormant synapses receive higher input due to damage elsewhere
• This causes a new pathway to open

Question 6

What are the three ways to support Neuronal Unmasking?

Answer 6

• Axonal Sprouting and Reformation of blood vessels
• Recruitment of homologous areas
• Denervation super-sensitivity

Question 7

What is Axonal Sprouting and Reformation of Blood vessels?

Answer 7

• Where new nerved endings grow and connect with undamaged areas.
• It creates a new blood vessels and pathways around the damaged area.

Question 8

What is Recruitment of homologous areas?

Answer 8

• Using existing structures on the opposite hemisphere to enable a route to be used without having to build new networks.
• E.g. if Broca’s area was damaged then an area of the right might take over.

Question 9

What is Denervation super-sensitivity?

Answer 9

• Axons with a similar function to the damaged ones, are more aroused and more sensitive to input.
• Loss of nerve supply to a particular area of the body, results in an increase in the sensitivity of the remaining nerves in that area.
• The nerves that used to supply the limb are no longer present, but the remaining neves in the area become hypersensitive, causing pain.
• Phantom limb occurs when rewiring takes place in the brain but it overcompensates in the somatosensory cortex when signals for pair are.
• As a result the person feels pain in a limb no longer present.

Question 10

Describe Maguire et al (2000)

Answer 10

• Unlike the grid pattern common to many capital cities, London streets generally present taxi drivers with a layout that is quite challenging to learn.
• To become licensed, black cabbies must demonstrate a thorough knowledge of streets and traffic patterns so that they can efficiently navigate between any two points.
• In this study, the demands on long-term memory as well as spatial reasoning were particularly significant because it was done before widespread use of SatNavs.
• Brains scans of the 16 London Taxi drivers showed a particularly large posterior hippocampus, a region of the brain that supports two-dimensional spatial processing.
• The posterior hippocampus was largest in taxi drivers with more than 40 years of experience navigating the streets of London.
• Increased grey matter was found in the brains of taxi drivers compared with controls in two brain regions, the right and the left hippocampi
• The increased volume was found in the posterior hippocampus

Question 11

Elbert et al (1985)

Answer 11

• A professional violinist relies on extraordinary finger dexterity in their left hand.
• Much less dexterity is required in the fingers of the right hand, which is responsible for bowing.
• Brain scans of the somatosensory cortex in violinists reveal an unusually large region
  devoted to the fingers of the left hand—much larger than the region that supports finger movement in the right hand.
• The asymmetry suggests that the brain has responded to then demands placed upon it - the brain adapts by recruiting neurons to help support finger control in the left hand

Question 13

What are the negatives of Plasticity?

Answer 13

• Examples of this would include: prolonged drug use leading to poorer cognitive functioning and in old age being associated with dementia.
• Both are due to changes in the brain.