Plasticity & Functional Recovery of the Brain After Trauma (AQA A Level Psychology)

Plasticity & functional recovery of the brain after trauma

• Neuroplasticity refers to the brain’s ability to adapt to change, be that from injury, damage due to illness or changes brought about due to learning and experience

• Structural plasticity refers to changes within brain structures e.g.

  • increased grey matter build-up in the posterior hippocampus due to learning experienced over time

    • Such changes do not happen immediately, they develop slowly, in response to either the degree of damage or the extent of the learning/experience

    • The buildup of grey matter is due to the increased synaptic connectedness in the brain regions involved

• Plasticity means that the brain is not a static, concrete mass; it is a flexible organ that responds and adapts to environmental stressors/stimuli

Examples of neuroplasticity

• London black cab taxi drivers spend years navigating and learning routes through central London

  • Their brains adapt by increasing grey matter in the posterior hippocampus, a brain region linked to spatial navigation (Maguire et al.2000)

• People who learn a juggling routine show increased grey matter in the mid-temporal cortex compared to non-jugglers

  • Once the juggling participants had ceased juggling for three months the grey matter linked to juggling began to decrease (Draganski et al. 2004)

  • The jugglers' brains thus showed evidence of neuroplasticity and neural pruning (the loss of grey matter)

• People who practice mindfulness show increased grey matter in the prefrontal cortex and decreased grey matter in the amygdala

  • The participants in this study reported a decrease in stress and anxiety symptoms (Gotink et al. 2016)

Functional recovery after trauma

• Functional plasticity (also known as functional recovery) refers to the brain’s ability to replace lost or damaged functions by using existing brain regions in their place

  • Functions such as mobility, memory and language are taken over by healthy brain regions capable of replacing the lost functionality

  • Functionality may never be 100% what it was before the loss but it serves as a good 'stand-in' when circumstances dictate

    • One example involves a child who had half of her brain removed (hemispherectomy) to control her epilepsy; she can function almost completely normally after surgery as her remaining hemisphere takes over the tasks of the hemisphere which have been removed

• Neural pruning (as occurred in Draganski's study above), allows the brain to be more efficient

  • Synapses that are used frequently grow stronger over time (plasticity), but synapses that are not used are 'cleared out' in a process called synaptic pruning

  • This allows the brain to be a more efficient tool, both structurally and functionally

• Danelli et al. (20213) conducted a case study of E.B., a 14-year-old boy with brain damage

  • At 2 years old, EB had to have a hemispherectomy on the left side of his brain to remove a tumour 

  • His language centres were removed, including Broca's and Wernicke's areas

  • Immediately after surgery, EB lost all language function

  • However, after two years EB had recovered his language ability, even without his left hemisphere 

    • fMRI scans showed that the right hemisphere was acting as if it was the left hemisphere in terms of language function

• The case of E.B. demonstrates functional recovery

  • The brain can adapt and recover after trauma

  • Functional recovery has something of a 'time stamp'

    • If the recovery takes place early in life the affected person has a chance of almost full recovery

    • For older people, this is less likely due to the ageing of the brain and a decrease in synaptic activity

• Functional recovery tends to begin with a rapid growth spurt then slow down and eventually plateau after some time

  • This should be reflected in the rehabilitative therapy that is given to patients with brain damage

Evaluation of plasticity & functional recovery

Strengths

• There is an impressive body of research into neuroplasticity, with findings supporting the idea that the brain adapts to change

  • If several different studies come to the same conclusion (in terms of neuroplasticity) then the theory has good internal validity

  • This means that researchers can exclude other explanations for their findings

• There are huge practical applications for both structural plasticity and functional recovery

  • Understanding the brain's capacity to compensate for loss and being aware of the slowing-down phase of functional recovery are key to informing therapy - both physical and cognitive - for patients with brain damage

Limitations

• Neuroplasticity and functional recovery do not always happen when needed e.g.

  • The case of H.M. who had his hippocampus removed at the age of 27

    • H.M. suffered from catastrophic anterograde amnesia

    • He never recovered any functionality: his memory (particularly short-term memory) was affected permanently

  • This casts doubt as to the universality of plasticity - it does not apply in every case

• Research in this field is correlational only

  • This means that cause-effect cannot be established

  • This is a limitation as it leaves too many unanswered questions e.g.

    • why does grey matter build up in specific brain regions?

    • what other possible factors could account for the grey matter?

    • how can cause-effect be found when the sample sizes used in the research are generally so small (e.g. Maguire only used 16 taxi driver participants)?