6. Plasticity and functionl recover of the brain after trauma

Plasticity

The brain ability to adapt both its function and structure due to changes in the environment. Changes in the environment include:

-learning new skills

-developmental changes

-brain injury (direct=to a specific area of the brain, indirect=damage such as brain bleeding from a stroke)

AO1 Plasticity

Neurones and Synapses

Brain is made up of neurones, they are connected by synapses, so info travels between neurones across synapses. As info passes through the brain, new neuronal pathways are formed.

Synaptic Connection in Childhood

During infancy, the number of synaptic connections increases rapidly, peaking at about 15,000 per neurone at 2-3 years old (twice as many as in adult brain).

Synaptic Pruning

As we go older, we go through the process called synaptic pruning. During it: weak and rarely used connections are deleted, strong and frequently used connections become stronger.

Maguire (2000) London Taxi Drivers

Aim: to investigate whether experience changes brain structure.

Procedure: Maguire used brain scans to compare post hippocampus of London taxi drivers and a controlled group of non taxi drivers. Taxi drivers have to learn large amounts of route info.

Findings: taxi drivers had a larger post hippocampus, in comparison to the controlled group.

Explanation: the positive correlation of the structure difference show plasticity, as the brain is able to adapt and change to the environment, in this case to improve memory formation.

Evaluations (Plasticity)

Age and Plasticity(plasticity is a lifelong ability rather than something that only occurs in childhood)

Ev: Research found that 40 hours of golf training, pp age 40-60 showed increased activation in the motor cortex, demonstrating that the brain continued to modify its neural connections and adapt in response to experience, despite the pp being well beyond childhood. Ex: shows that brain remains capable of reorganising itself and forming neural pathways throughout the lifespan, so plasticity is not limited to early development and can occur in adulthood when individuals learn new skills.

Negative plasticity (brains ability to adapt in not always beneficial)

Ev: Brain adapts to the environment, which means it adapts to prolonged drug use. Research found that the brain adaptation to drug use leads to poorer cognitive function and an increased risk of dementia. Ex: challenges the view that plasticity is always advantageous because the changes that occur may have negative consequences for cognitive functioning.

Research support (experience can physically alter the structure of the brain)

Ev: Maguire used MRI scans to compare the brains of London taxi drivers with non taxi drivers. They found that taxi drivers had a larger posterior hippocampus and that the size of this ares positively correlated with a number of years spent working as a taxi driver. Ex: demonstrates that repeated experience and environmental demands can lead to structural changes in the brain. So brain is capable of adapting and recognising itself in response to learning and experience.

Functional Recovery (AO1)

-It’s the brain ability to redistribute or transfer functions that were previously carried out by damaged brain areas to other undamaged areas (functional reorganisation). Functions that were performed by the damaged area are taken over by healthier areas of the brain.

-Function recovery happens quickly after trauma (spontaneous recovery) and then slows down after several weeks or months. During this period, the brain reorganises and rewires itself to compensate for damaged areas.

Mechanisms of Functional Recovery:

1. Atonal sprouting- the growth of new nerve endings which connect with other undamaged neurons to form new neural pathways. When an injury damages an existing neural pathway, new connections grow from surviving neurones. These pathways allow communication to continue despite the damage.

2. Denervation Supersensitivity- when neurons lose some of their incoming connections, the remaining axons become more sensitive. The surviving neurones become more likely to fire in response to stimulation, which compensates for the loss of neurons in the damaged pathways. (negative consequences= oversensitivity to messages such as pain)

3. Recruitment of homologous areas- the opposite hemisphere takes over functions previously performed by the damaged area. A homologous area on the other side of the brain carries out the lost function. (If Broca’s area in the LH is damaged, the RH equivalent may take over speech production. After recovery, functioning may gradually shift back to the original hemisphere).

Factors that make functional recovery more likely (AO1)

-Age. Children show the greatest ability to recover. Adults can recover too, but generally less effectively.

-Gender. Women appear to recover more successfully from brain damage than men.

-Rehabilitation Therapy. Focused rehabilitation and practice improvement recovery outcomes. Recovery is more successful when patients actively engage in therapy

Evaluations (Functional Recovery)

Supporting evidence

Ev: Patient EB underwent a LH at the age of 2,5 which involved the removal of both language areas (Broca and Wernickes). Despite this, over a two year recovery period regained almost full language functioning. fMRI scans showed that language functions had been transferred to the RH. Ex: supports functional recovery, as it shows the recruitment of homologous areas. The RH equivalent of the language areas took over the functions previously carried out by the damaged LH. So findings support the idea that the brain can reorganise itself and redistribute functions following trauma.

Real world example

Ev: research has improved psychologists understanding of how the brain recovers following injury and has led to the development of rehabilitation programmes designed to promote recovery. Ex: knowledge can be applied to help patients recover from strokes, brain injuries. Understanding processes like functional recovery and atonal sprouting allows therapists to develop more effective rehabilitation techniques, improving patients quality of life and increasing the practical value of the research.

Evidence that recovery is influenced by age

Ev: research suggests that children show the greatest capacity for functional recovery following brain injury, whereas recovery become less effects with increasing age. Ex: demonstrates that brain retains the ability to reorganise itself after damage. The greater recovery shown by younger individuals suggests that neural plasticity and functional reorganisation are particularly effective early in life. Findings provide support for the brains ability to adapt following trauma.