Brain Plasticity

• Brain Plasticity 


  is the brains ability to reorganise it's neural pathways as a result of experience and new learning.
• Synaptic pruning 


  is the process in which the brain removes neurons and synapse that it doesn't need.

  -During infancy, the human brain experiences rapid neuronal growth. The synaptic connections are peak at 2/3 years. As we age the synaptic connections used regularly are strengthened and remain.
• Research into plasticity - Maguire

  Aim- to examine whether structural changes in the brain could be detected in people with extensive experience of spatial navigation.

  Method - Structural MRI scans were obtained of 16 right-handed male London taxi drivers with 1.5 years of experience. compared them to 50 healthy right handed males who don't drive taxis (control group).
• Research into plasticity - Maguire

  Results - more grey matter (more connections) was found in taxi drivers. A positive correlation was found between time spent as a taxi drover and grey matter volume.

  Conclusion - the observed structural changes support brain plasticity. Significant differences between hippocampi of taxi driver and control group, suggests extensive practice of spatial navigation results in structural changes.
• Research into plasticity - Draganski

  -Draganski obtained structural MRI scans of thee brains of medical students 3 months before and after their medical exam.

  -He observed changes in grey matter of the posterior hippocampus after the exam.

  -He concluded that structural changes were because of the intense learning that had taken place as a result of studying.

  -Evidence of plasticity is as a result of experience and learning.
• Research into plasticity - Jugglers

  -24 Volunteers aged 20-24 years took part in the study and all had no juggling experience.

  -Each PP had a baseline MRI scan at the start.

  -PP were randomly allocated to one of two conditions: one group was taught to juggle and one group not.

  -Second MRI scan revealed more grey matter in mid-temporal area (visual) both hemispheres in juggler group than control group which supports plasticity.

  -However, difference diminished 3 months after studying which supports synaptic pruning.
• Neurological changes make functional recovery possible:

  -Recruitment of homologous areas: similar area of the brain gets recruited to function, the brain on the opposite hemisphere to trauma may begin to specialise in performing lost functioning.

  -Denervation supersensivity: the surrounding receptors become supersensitive to neurotransmitters to compensate for loss of sensitivity at the damaged area.
• Neurological changes make functional recovery possible:

  -Neural unmasking: neural pathways that didn't carry out any function are now activated and unmasked to enable functioning to continue.

  -Axonal sprouting: the growth of new dendrites and axon terminals to allow new synaptic connections to be made with undamaged nerves.

  -Reformation of blood vessels: providing oxygen and nutrients to promote new neural growth and recovery.
• Research about the factors which influence plasticity:

  -Age: plasticity decreases with age. Brain is more able to reorganise its structures as it's adapting constantly to new experiences and learning.

  -Cognitive reserve: intelligence level, functional recovery is dependant upon a persons level of 'cognitive reserve' before trauma.

  -Gender: research suggests women have a greater potential for plasticity and functional recovery than men.
• Case study of E.B - Danelli et al

  -E.B had a trauma in his left hemisphere and got it removed. All his linguistic abilities disappeared.

  -He underwent an intensive rehabilitation programme and his language started to improve at age of 5.

  -Danelli tested him at the age of 17 to compare his language abilities. They found that the right hemisphere compensate for the loss of left hemisphere, the functioning linguistic ability.
• Case study of E.B - Danelli et al

  -This study contributes to understanding of plasticity, concluded that the right hemisphere had compensated for loss following intensive programme but will never be fully compensated.

  -Issues with replication as unethical to replicate the situation so can't test for reliability.

  -Issues with generalisation as there is a small sample size as it's a unique situation.
• Evaluation - brain plasticity and functional recovery

  -Practical application: strength of research is neuroplasticity. Understanding plasticity at any age is possible so motivating and encouraging for the patient. more likely to continue to the end.

  -Research has resulted in 'constraint-induced movement therapy'. The patient practices moving the affected part of the body while unaffected part is restraint. encourages growth of synaptic connections.

  -Suggests growth of synaptic connections has positive implications for patients in recovery from trauma to the brain.
• Process of plasticity can be negative:

  -Brains ability to reorganise it's structure is not always an advantage.

  -Overexposure to drugs can results in brain plasticity which has negative implications for the user.

  -E.g. chronic nicotine use can result in desensitised dopamine receptors and changes in reward pathway, contributed to withdrawal syndrome.

  -60-70% of amputees develop phantom limb syndrome which occurs due to changes in somatosensory cortex following loss of a limb.