Split brain surgery and plasticity and functional recovery of the brain after trauma
Split brain patients
Some sufferers of epilepsy who do not respond to drug treatment are given an operation that involves cutting the corpus callosum so that the effect of the disorder is reduced by containing it within one hemisphere of the brain. An effect of this is that the two hemispheres can no longer ’communicate’ with each other and studies of such ’split brain’ patients have allowed psychologists to investigate the role of each hemisphere. After surgery the hemispheres act separately, making an individual feel like two people in one body. Some patients develop techniques to allow the hemispheres to communicate with each other and strategies to compensate for the lack of connectivity, for example turning their heads so both hemispheres can perceive an environment.
Plasticity and functional recovery after trauma
Most people who incur brain damage can make some recovery and in some instances the brain can adapt and find another way to complete a function. Level of recovery is dependent on the type and severity of trauma.
Plasticity is the brain’s ability to replace a function lost by anatomical damage. Cell bodies cannot be replaced, but in some instances axons (part of a nerve cell) can. There are three main anatomical ways that the brain can replace axon function:
1 Increased brain stimulation — if the undamaged hemisphere is stimulated, recovery from a stroke can improve.
2 Axon sprouting — damage to an axon results in lost connections to adjoining neurons, but their neighbouring neurons can grow extra connections to compensate. This can replace function if the damaged axon and the replacements perform similarly.
3 Denervation supersensitivity — axons that perform similarly to damaged ones can become aroused to a higher level to compensate.
Functional recovery of the brain after trauma
Rehabilitation can help the brain compensate for loss of function by an individual learning how to use their working faculties and functions to compensate for those lost to injury. Several factors affect recovery:
1 Perseverance — sometimes a function may appear lost, but it is because an individual isn’t ’trying’ hard enough. Perseverance can eventually restore some function.
2 Physical exhaustion, stress and alcohol — recovering function can be exhausting and stress and alcohol consumption can affect the ability to use recovered functions.
3 Age — recovering function can become more difficult with age.
4 Gender — women appear more able to recover from trauma as their function is not as lateralised (concentrated in one hemisphere).
Schneider et al. (2014) investigated whether the amount of time spent in education affected recovery from brain injury. The amount of education of 769 patients receiving rehabilitation for head injuries was recorded. It was found that those receiving a lengthier education had greater recovery. This suggests that people remaining in education for longer have a greater ’cognitive reserve’ that allows them to maintain function in spite of damage and to regain function after injury.
• Fleet & Heilman (1986) found that heightened stress levels and alcohol consumption lessened the ability to use regained function after brain injury, illustrating how environmental factors can affect the ability to recover from trauma.
• Sperry (1968) examined split brain patients to find that different functions are carried out by the two hemispheres of the brain. This supports the idea of lateralisation of function, that different brain areas are involved with differing tasks.
• Danelli (2013) reported on the case study of a boy who having lost his left hemisphere due to a tumour (which controlled his language abilities) recovered most of these abilities. This suggests the right hemisphere compensated for the loss, supporting the idea of the brain having plasticity.
Split brain research has proved a useful means of investigating and understanding the functions of each hemisphere of the brain.
Research indicates that recovery from brain injury is nearly always possible, giving hope for the future for those unfortunate enough to suffer brain traumas.
Split brain research is carried out on people with severe epilepsy, so the extent to which findings can be generalised to people without such a disorder is questionable.
The extent to which people can recover from brain injuries is subject to great individual differences, which suggests generalisable conclusions are difficult to draw.
The level of function within specific brain areas before injury has taken place is generally unknown, making comparison with post-injury function levels difficult to achieve.
Research into split brain and brain injury patients has contributed greatly to the establishment of effective rehabilitation programmes to help people recover lost function. This is especially beneficial to the large number of people suffering strokes.