Plasticity and Functional Recovery of the Brain After Trauma

Plasticity and Functional Recovery of the Brain After Trauma: Psychology

The brain contains billions of neurones the likes of which are connected by synapses. Information travels between neurones, and each piece of new information creates new neuronal pathways.

Fig. 2: The brain contains around 86 billion neurones.

By revising and repeating information through reading or practising a certain activity, the pathways become stronger. When we don’t repeat or practise a piece of information for a while, it becomes weaker, and in some cases, it is removed altogether, especially during development. This is known as synaptic pruning.

Neural reorganisation is more active in those who are younger. Newborns and children will constantly undergo this pruning process and will have more neurones and neuronal pathways than a young adult, and a young adult will have more than an adult. This doesn’t mean that adults are incapable of utilising the brain’s plasticity. More, it highlights how, during development, different types of neuroplasticity occur.

The brain can also form new connections with neuronal cell bodies, forming additional branches and axons, known as axonal sprouting.

Axonal sprouting is a form of plasticity similar to neural regeneration: when an area of the brain is damaged, new neurones and connections are generated. Overall, this affects the structure of the brain and can appear in scans such as MRIs.

There’s evidence to say that taking certain addictive drugs for some time causes structural plasticity changes. This was demonstrated by Kolb and Robinson (2004). They found that addictive substances such as nicotine and morphine cause changes in the structure of dendrites and dendritic spines in brain regions such as the nucleus accumbens and the prefrontal cortex.

What is Functional Recovery Psychology?

Functional recovery psychology aims to transfer the function of damaged brain areas to undamaged regions to rehabilitate functions.

Psychology research has found that brain regions compensate and occasionally specialise and take the function of damaged brain regions; this concept is known as plasticity.

Functional Recovery Definition: Trauma and Recovery

Functional recovery is possible in the brain. Functional recovery refers to the brain's ability to regain function after experiencing trauma, be that through disease or injury, made possible by neuroplasticity. Let’s see some examples.

Trauma to the brain can happen in one of two ways:

1. Direct: damage occurs due to being hit in some form in the head (for instance, if someone were to fall over and bang their head).

2. Indirect: damage occurs due to swelling, bleeding (for instance, if someone has a stroke), or oxygen deprivation to brain regions.

When there is a loss of axons in a pathway due to direct or indirect trauma, the remaining axons become more sensitive as a result. This means they are more likely to ‘fire’.

This is known as denervation hypersensitivity.

• Baranauskas and Nistri (1998) found that consistent, intense, or noxious (painful or harmful) stimuli to neurones will cause sensitisation. They described it as one of the fundamental forms of synaptic plasticity.

  • Nociceptors are types of neurones, usually found in the skin, that are responsible for detecting extremes in temperature and pressure and injury-related chemicals.

  • In the spinal cord, repeated stimulation of the dorsal roots, including nociceptive nerve fibres, can cause progressive increases in the number of action potentials (the nerve ‘firing’, in a sense) generated by motoneurones and interneurones found there.

  • This consistent firing increases the sensitivity of these neurones, and, ultimately, increases the spine's sensitivity to pain.

• Cannon and Rosenblueth (1949) demonstrated the ‘law of denervation,’ which states that surgical denervation causes supersensitivity in neurones. The closer the neurones are to the damaged areas/cut neurones, the greater the supersensitivity. This decreases the chain of neurones.

Fig. 3: Neurones become more sensitive when close to damaged areas.

Functional Recovery Examples: Healthy Areas Compensate for Damaged Areas

After the brain is damaged, for instance, if a person slips and bangs their head in an accident, healthy areas of the brain compensate for the damaged areas, known as functional recovery. This can occur through neuroplasticity (which we discussed above), neuronal unmasking, or through stem cells (research is still being conducted on this.)

This process overall is known as functional reorganisation.

Stem cells (cells that can take on characteristics of any type of cell) can potentially be implanted to replace the damaged cells.

Functional recovery is affected by:

1. Age: children, particularly newborns, have the best ability to recover, more so than young adults and adults. There is a negative correlation between ageing and functional recovery.

2. Gender: women can recover more from brain damage than men.

3. Therapy: rehabilitative therapy increases the ability to recover a function. For example, if there is paralysis in a limb after a head injury, in therapy they would focus on the paralysed limb to help it recover.
4. Education: those who had a higher level of education were more likely to have a speedier recovery from brain injuries.

Rehabilitation Roles in Plasticity and Recovery

Rehabilitative therapy can be used in the form of constraint-induced movement therapy (CIMT). During CIMT, patients are prevented from using coping strategies and are effectively forced to use the affected area of lost function.

The function is transferred through neural reorganisation. Issues with CIMT exist however, in that CIMT has to be very intensive and is often uncomfortable and frustrating for patients. The more damage to the brain sustained, the more therapy is required, and the harder it is to regain function.

Plasticity and Functional Recovery of the Brain After Trauma Evaluation

Let’s discuss the validity of the studies on plasticity and functional recovery of the brain.

• Maquire et al. (2000) studied a group of 16 male taxi drivers, comparing them to a control group. Taxi drivers in London have to undergo a test called ‘The Knowledge’ to prove they can remember the vast amounts of streets and routes in London.

  • ‘The Knowledge’ is incredibly extensive and requires up to two years of studying.

  • The study required taxi drivers to have been working for at least 1.5 years.

  • Researchers found that the posterior hippocampus, responsible for spatial memory in the form of navigation, was significantly larger in taxi drivers. It was also positively correlated with the time spent working as a taxi driver.

  • This suggests the physical structure of the brain can change depending on the environment and the experiences of the individual. The brain can reconfigure itself and adapt to the psychological demands of improved memory formation.

• Danelli et al. (2013) assessed a 14-year-old patient, known as EB. EB was born with a tumour in their brain, and at the age of two, they underwent a left hemispherectomy (removal).

  • This removed important, well-known areas of the brain: Broca’s area, and Wernicke’s area, the language centres.

  • EB lost nearly all of their language capabilities after surgery, however, after two or so years, they regained nearly full use of their language abilities, although it was still more taxing for them mentally.

  • EB developed normally, with a few issues (dyslexia.)

  • Researchers found in the fMRI images of EB’s brain, that the right hemisphere had adapted and changed structurally, to the point of ‘matching’ a similar structure that language centres lost in the left hemisphere would have had.

  • This suggests the brain can recover after significant damage or injury. The right hemisphere adopts roles normally taken by the left.

• Overall, the results of this study help those in rehabilitative therapies. Physiotherapists can confidently use focused therapy styles to help people return to normal lifestyles.

• This study gives us a deeper understanding of the nuances of the brain. Such a complex organ requires extensive research, and this research is constantly being assessed and updated.

Phineas P. Gage

A famous case study is that of Phineas P. Gage. In 1848, he was working on a railway, packing explosives into the ground with an iron bar.

Fig. 4: Phineas P. Gage suffered damage to his left frontal lobe.

The explosives went off, and the bar went through his skull and through his left frontal lobe. At first, Gage could walk and talk. Then, he collapsed and his health deteriorated over the next few days, where he was in and out of a coma.

After 24 days Gage was effectively back to normal. However, he had memory loss and anger issues after the injury (something his friends noted). He lived for 12 more years.

Phineas Gage is a great example of plasticity and functional recovery in action. He lost portions of his brain, received a significant injury to the remaining portions close by, and still was able to recover despite the loss.