brain recovery / neuroplasticity

traumatic brain injury

TBI is caused by blow to the head where frontal and temporal lobes are usually injured. It causes impairments to memory, cognitive ability, social communication and emotional regulation and is consistently linked with earlier, more frequent and violent offending.


Phineas gage:

  • Suffered frontal lobe brain damage when a rod went through his brain while working on a railroad

  • He lost mostly white brain matter (11%) compared to grey matter (4%), which has the ability to regenerate and explains his quick (6 month) recovery

  • He became highly aggressive, agitated and impatient — disinhibited

  • Harlow: brain has localised function as damaged part controlled reasoning and restraint which was compromised

  • However, this case could be used to support holism, as he was able to function normally, despite losing brain matter

  • Problems with the study: small sample, misinfo and less knowledge at the time — makes this story hard to draw conclusions and generalisations for


plasticity

Plasticity is the brain’s ability to change and adapt, usually through regeneration or reorganisation, as a result of experiences, learning or damage.

After brain damage, some recovery is usually made through either:

  1. New branches of axons and dendrites growing between neurons to areas of damage

  2. The brain finding another way to complete a function that was originally associated with the damaged area


Ways axons can be replaced:

  • Increased brain stimulation

    • Neighbour neurons that connect with damaged neurons no longer have inputs, stimulating them can improve recovery

    • E.g electroconvulsive therapy

  • Axon sprouting

    • Damaged axon lose connections, they can re-sprout on neuron or neighbouring neuron in replacement

  • Denervation super sensitivity

    • Axons that do similar job can become aroused at a high level to compensate lost ones

    • Replaces lost function but can cause oversensitivity to messages like pain levels


Neuroplasticity studies:

  • Gopnik et al — 2-3 year old: 15,000 synaptic connections, 2x as many as adults

    • Synaptic pruning is the deletion of unused pathways and strengthening of frequent connections

    • Critical period of plasticity

  • Maguire et al — taxi drivers have more grey matter in their hippocampus than match control group

    • Linked to spatial awareness/navigation

    • Longer in the job, more pronounced difference

  • Draganski et al — medical students 3 months before and after exam, changes found in posterior hippocampus and parietal cortex

  • Mechelli et al — bilingual participants had larger parietal cortex


Localisation studies:

  • Dougherty et al — 44 OCD patients with cingulotomy (lesioning of the cingulate gyrus), in 32 weeks 1/3 had successful response

    • Suggests symptoms/behaviours of mental disorders are localised

  • Lashley — 10-50% of rat’s cerebral cortex removed, still able to learn a maze, proves that no area is more important

    • Learning is too complex to be localised, whole brain involved

    • However, humans have more highly developed cerebral cortex so it is difficult to draw conclusions

    • ‘Law of equipotentiality’ that any part of brain can perform any function (holism)


functional recovery

Functional recovery is brain plasticity as a result of brain damage, by transferring damaged functions to undamaged areas of the brain.

  • Axon sprouting — growth of nerve endings

  • Reformation of blood vessels

  • Recruitment of homologous areas on opposite side to perform tasks


Hemisphere removal:

  • Danelli et al

    • EB, operated on at 2 ½ to remove tumour in LH

    • His linguistic ability was impaired

    • Intensive rehab = no language problems by 8

    • At 17, he was tested and it was found that his RH had compensated and taken over his language abilities, but he still had some problems with grammar and naming objects compared to control group

  • Jodie miller case study

    • 3 years old, she suffered seizures caused by her RH, the hemisphere was removed

    • She was able to walk soon after surgery and lives a functional life even today


Factors that affect brain recovery:

  • Perseverance — dependant on whether the individual puts work and practice into recovery or decides they can’t do it (practice = plasticity)

  • Age — old age affects recovery due to weakening levels of plasticity over lifespan

    • Marquez de la plata et al: older patients had less function after brain damage than younger patients

  • Exhaustion/stress/alcohol — takes a lot of effort to regain functions, these factors make it harder as energy is needed for plasticity

  • Gender — women recover better because it is believed that their brain function isn’t as lateralised


Education on recovery — Schneider et al:

  • Aim — investigate if time spent in education is a factor in recovery from brain

  • Procedure — 769 people who suffered head injuries followed rehab programme

    • 25% had not finished school, 50% had 12-15 years education, 25% graduated university

  • Results — 40% of uni students left free of disability, only 10% who left school early made full recovery

  • Conclusion — education is a factor in recovery, suggests that it leads to a higher cognitive reserve and using brain more effectively for compensating function


Evaluations of plasticity/functional recovery:

  • EB study: ease studies can be weak since they’re not representative and might not consider all the factors that could cause the recovery

  • Schneider study: Correlation-causation relationship instead of cause-effect relationship, cannot be proven that education was the sole factor

  • Using fMRIs for research is highly scientific, valid and precise

  • Practical application, contributes to neurorehabilitation techniques

    • Medina et al — prolonged use of drugs results in poorer cognitive functioning/dementia

    • Ramachandran and hirstein — 70% of amputees experience phantom limb syndrome

  • Plasticity shown to reduce with age, but still continues throughout life

    • Bezzola et al — 40 hours of golf training for 40-60 year olds changes neural representation of movement