Plasticity and functional recovery of the brain after trauma

Question 1

What is plasticity?

Answer 1

• The ability of the brain to change and adapt its synapses, connections and structures after an experience.
• Could be positive - new memory is formed.
• Can also occur after brain trauma so it must adapt to any damage.

Question 2

Brain plasticity

Answer 2

• Present from birth
• During infancy the brain rapidly grows the number of synaptic connections, peaking at 15000 at 2.5 years old. - twice as many as an adults and reflects the vast amount of learning a baby has to do.
• Connections that are unused are deleted and frequently used ones become stronger - synaptic pruning.
• Scientists used to think pruning only occurred in childhood, evidence suggests the ability continues to adulthood.

Question 3

Functional Recovery

Answer 3

• Takes place after trauma such as brain injury or stroke.
• Where brain functions are transferred from damaged to undamaged areas.
• Healthy areas take over from parts that are missing, damaged or destroyed.
• Neuroscientists believe this occurs quickly after trauma - spontaneous recovery - slows down after several weeks/months.
• Person may require rehab therapy to further recovery.
• Recovery not always complete - depends on degree of damage.

Question 4

Anatomical changes that occur during functional recovery

Answer 4

• Axon sprouting - when axon damaged, affects neighbours as they no longer receive input from it. Neighbouring neurons sprout extra connections to compensate. Usually happens two weeks after damage. If damage and new axons do similar job, function more likely to return.
• Denervation supersensitivity - when axons do similar job to damaged one they become aroused to compensate for lost ones. Can have unfortunate consequence if involved in carrying pain messages, pain levels increase.
• Reformation of blood vessels - brain very reliant on good blood supply to bring oxygen and energy, important for recovery that blood supply is consistent.
• Recruitment of homologous areas in other hemispheres - similar areas in opposite hemisphere can be used for specific tasks. Can be temporary or permanent solution.

Question 5

Factors affecting recovery rates

Answer 5

• Perseverance and stress - some evidence if a person assess that function is lost and does not try to use it, less chance of recovery. Takes a lot of effort to use something that is damaged resulting in fatigue. Stress and alcohol consumption seem to affect chances of function being regained.
• Age - Marquez de le Plata found that following brain trauma older patients regained less function than younger ones. Follow up measurements 5 years later also showed that younger patients had less decline.
• Gender - research suggests women recover better as their function is not lateralised

Question 6

Research studies on plasticity - Draganski and Maguire

Answer 6

• Draganski Carried out brain scans on medical students 3 months before their final exams and again afterwards.
• Identified learning induced changes in the posterior hippocampus and parietal cortex.
• Maguire found that posterior hippocampal volume of London taxi drivers brains was positively correlated with their time as a taxi driver and that there were significant differences between taxi driver brains and those of controls.
• Shows that the brain can permanently change in response to frequent exposure to a particular task.
• Studies support the idea that the brain has plasticity and there are physical changes that take place when learning.

Question 7

Research studies on functional recovery

Answer 7

• Schneider studied 769 p who had brain injury following a road traffic accident or fall. Progress in rehab was monitored.
• Findings - after one year 28% made full recovery and were back in education or working. 39% of graduates were left disability free compared to only 10% who had left school early.
• P who were graduates were 7 times more likely to make a full recovery.
• Argued that this difference could be because the more educated people make more effective use of their brains, strengthens them. Greater cognitive reserve.
• People with increased cognitive capacity may heal differently as they have a greater ability to compensate for function.
• Study suggests a further individual difference in brain recovery after injury. Cannot generalise about likelihood of recovery and every patient needs own rehab programme.

Question 8

Evaluation of brain plasticity and functional recovery - practical application

Answer 8

• Understanding processes involved in plasticity has led to the field of neurorehabilitation.
• Techniques have been divised to help rehab process - movement therapy and electrical stimulation
• Strength - suggests the brain can fix itself to a certain extent. Patient needs further intervention to increase chances of full recovery.

Question 9

However - practical application

Answer 9

• A lack of pre trauma info is a common issue in this area of research.
• No baseline comparison so difficult to know extent to which brain has recovered.
• Weakness - makes research less scientifically robust suggesting it is not predictable who will recover most after brain trauma.

Question 10

Evaluation of brain plasticity and function recovery - animal research

Answer 10

• Early studies in 60s and 70s showed plasticity of brains in animals.
• Hubel and Wiesel sewed one eye of a kitten shut and analysed brain responses. Found that visual cortex associated with shut eye was not inactive as predicted but continued to process info from open eye.
• Strength - supports human research on plasticity in a more scientfic and controlled way. Researchers allowed to carry out procedures on animals which has provided a more empircal set of evidence for plasticity.H

Question 11

However - animal studies

Answer 11

• animal research clearly has ethical issues as it causes permanent damage to animals which breaks animal act 1979.

Question 12

Evaluation of plasticity and functional recovery - scientific research

Answer 12

• The research in this area uses very controlled measuring tools in order to help the patient recover.
• fMRI and speech assessments
• Strength - an objective and reliable way of assessing each patient.

Question 13

However - scientific research

Answer 13

• Incidents where the rewiring that the brain does has a negative consequence.
• Ramachandran and Hirstein found that 60-80% of amputees experience phantom limb syndrome which is unpleasant and painful. Thought that this is due to cortical reorganisation in the somatosensory cortex after limb loss
• Weakness - suggests that plasticity is very complex and there are individual differences in the outcome. Further research needs to be done in this area to help prepare patients better for rehab.