Plasticity and Functional recovery

• Plasticity is the concept where the brain is able to adapt and recover from changes within the environment (trauma).
• The word plasticity is used to show the malleability and ‘plastic‘ nature of the brain - neural pathways which are used most often are strengthened whereas less frequently used connections are ‘pruned’ away.
• Research support: video games and meditation.

  -When comparing a control group to a group that was trained to play video games, researchers found increased grey matter in the cortex, hippocampus and cerebellum.

  -Compared 8 monks with 10 students - increased gamma waves in monks permanently, only slight increase in students while meditating.
• Functional recovery after trauma: the brain’s ability to recover itself after a traumatic event. The mechanisms for this are recruitment of homologous areas, axon sprouting and neuronal unmasking.
• Recruitment of homologous areas: the brain allocates the function of a damaged region of the brain to a different region of the brain - usually to a similar region on the opposite hemisphere.
• Axon sprouting: in a region where there is damage to the brain, existing neurons extend their nerve endings to compensate for loss of connections.
• Neuronal unmasking: when a surrounding area Of the brain is damaged, dormant synapses become active and create connections to typically inactive regions of the brain.
• Alternative treatments (stem cells): stem cells are unspecialised cells which can differentiate into a number of specialised cells. When implanted into the brain, they take on the role of neurons and directly replace dead or damaged cells.
• Strength of plasticity - support from Maguire’s taxi drivers.

  + Maguire conducted a study to compare the volume of grey matter in taxi drivers with non-taxi drivers.

  + Found that hippocampal volume was significantly higher in taxi drivers (using MRI) and was positively correlated with the time spent as taxis drivers.

  -However its hard to establish cause-and-effect as people may have naturally larger volumes of grey matter making them suitable for their job.
• Strength of plasticity - research support from rats.

  + An enriched environment increases number of neurons in the brain for rats.

  + In complex environments, rats showed an increase in hippocampal neurons compared to a simple environment.

  -However animal studies cannot be generalised to human brain structure. Humans have a much larger cerebrum than rats which is generally more complex.
• Strength of functional recovery - role of stem cells

  + Taijiri implanted stem cells into the brains of rats with brain injury, and saline solution into a control group with damage.

  + After 3 months the stem cells into rats showed development of neuron-like cells in the damaged region of the brain, not evident in control.

  -However animal studies are not generalisable to human brain structure etc.
• Strength of functional recovery - research support in humans

  + Human echolocation is a learned ability where people see the world through sound.

  + Blind people use this technique to navigate - studies using fMRI has shown that parts of the brain formerly used for visual processing adapted for the skill of echolocation.

  + Hence showing recruitment of homologous areas in humans.

  -Small sample sizes and small-scale studies limits clarity.
• During infancy, the brain experiences rapid growth in synaptic connections, however with age there is a cognitive decline. Older people have less plasticity and a smaller cognitive reserve.