plasticity

• Gopnik et al (1999) found that during infancy the brain experiences a rapid growth in the number of synaptic connections that it has
• Growth of synaptic connections peak at about 15,000 per neuron at 2-3 years of age, this is twice as many as there are in the adult brain
• As we age synaptic pruning occurs where rarely used connections are deleted and frequently used connections are strengthened
• Synaptic pruning enables lifelong plasticity
• Draganski et al. (2006)

  • studied medical students 3 months before and after their final exams
  • learning induced changes were seen to have occurred in the posterior hippocampus and parietal cortex
• Maguire et al. (2000)

  • looked at brains of London taxi drivers through MRI scans
  • found significantly more volume of grey matter in the posterior hippocampus than a matched control group
  • this part of the brain is associated with the development of spatial and navigational skills
• Maguire et al. (2000)

  • London taxi drivers learning experience of recalling city streets and routes for a complex test they have to take altered the structure of their brains
  • the longer the taxi drivers were on the job the more pronounced the structural difference was, representing a positive correlation
• Tramotin and Brenowitz (2000)

  • seasonal changes in response to the environmental changes
  • e.g. SCN on the sleep/wake cycle
  • evidence that SCN shrinks in all animals during spring and expands in autumn
  • BUT much of the work on seasonal plasticity is done on animals specifically songbirds
  • human behaviour may be controlled differently
• One limitation of brain plasticity is that it may have negative behavioural consequences. The brain's ability to adapt to damage is not always beneficial.
• Negative plasticity research - Medina et al. (2007)

  • brain's adaptation to prolonged drug use leads to poorer cognitive functioning in later life and increases risk of dementia
• Negative plasticity research - Ramachandran and Hirstein (1998)

  • 60-80% of amputees develop phantom limb syndrome - the continued experience of sensations in missing limb as if still there
  • sensations are unpleasant and painful
  • thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss
• Plasticity

  This describes the brain's tendency to change and adapt as a result of experience and new learning. This generally involves the growth of new connections.