Plasticity and functional recovery

• Brain plasticity

  = refers to the brain’s ability to change and 

  adapt as a result of experience. This ability 

  to change plays an important role in brain 

  development and behaviour.

  During infancy the brain grows in the number of synaptic connections (peaks to 15 000 by 3 years old ish – Gopnik et al 1999). This is twice as many as in the adult brain

  As we age, rarely used connections are deleted and frequently used connections are strengthened (synaptic pruning)
• Brain plasticity

  Researchers used to believe that changes in the brain only took place during infancy and childhood, but more recent research has demonstrated that the brain continues to create new neural pathways and alter existing ones to adapt to new experiences as a result of learning. 

  As we gain new experiences, nerve pathways that are frequently used develop stronger connections, whereas neurons that are rarely or never used eventually die.

  By developing new connections and pruning away weak ones, the brain is able to constantly adapt to a changing environment.
• Hebbian theory!

  Donald Hebb was one of the first to propose this idea that neurons form networks and that these networks strengthen the more we use them. 

  Cells that fire together, wire together
• Plasticity: As a result of life experience

  However, there is also a natural decline 

  in cognitive functioning with age that 

  can be attributed to changes in the brain. 

  This has led researchers to look for 

  ways in which new connections can be 

  made to reverse this effect.

  Boyke et al (2008) found evidence of brain plasticity in 60 yr. olds taught a new skill – juggling. They found increases in grey matter in the visual cortex, although when practicing stopped, these changes reversed.
• Plasticity: As a result of playing video games

  Playing video games involves many different complex cognitive and motor demands.

  Kuhn et al (2014) compared two groups - one a control group and the other who were trained for 2 months, att least 30 mins per day on the game Super Mario. 

  Findings =  Significant increase in grey matter in various brain areas including the cortex, hippocampus and cerebellum. This increase was not evident in the control group.
• Conclusions =  Video game training had resulted in new synaptic connections in brain areas involved in spatial navigation, strategic planning and working memory and motor performance - skills that were important in playing the game successfully.
• What is the main focus of the study on plasticity mentioned in the material?

  The effects of meditation on brain function
• What did researchers working with Tibetan monks demonstrate about meditation?

  Meditation can change the inner workings of the brain
• How many practitioners of Tibetan meditation were compared in the study by Davidson et al (2004)?


  8 practitioners
• How many student volunteers were compared in the study by Davidson et al (2004)?

  10 student volunteers
• What was the method used to measure brain activity in the study?

  Electrical sensors were fitted to both groups
• What type of brain waves showed greater activity in the monks during meditation?

  Gamma waves
• Why are gamma waves important according to the study?

  They coordinate neuron activity
• How did the gamma wave activity of the monks compare to that of the students during meditation?

  The monks had much greater gamma wave activity
• What was observed about the students' gamma wave activity while meditating?

  They showed only a slight increase in gamma wave activity
• What conclusions can be drawn from the study regarding meditation and brain function?

  • Meditation changes brain workings in the short term
  • May produce permanent changes in brain function
  • Monks had more gamma wave activity even before meditating
• AO3 - Plasticity

  (+) research support from animal studies

  Kempermann et al (1998) investigated whether an enriched environment can alter the number of neurons in the brain. 

  They found evidence of an increased number of new neurons in the brains of rats housed in complex environments compared to rats housed in lab cages. In particular, the rats housed in complex environments showed an increase in neurons in the hippocampus, a part of the brain associated with the formation of new memories, and the ability to navigate form one location to another.
• AO3 - Plasticity

  (+) Maguire et al (2000) studied London taxi drivers to discover whether changes in the brain could be detected as a result of their extensive navigational experience. 

  Using an MRI scanner, the researchers calculated the amount of grey matter in the brains of taxi drivers and a set of control ppts. 

  Findings = The posterior hippocampi of taxi drivers were significantly larger relative to those of control ppts and posterior hippocampal volume was positively correlated with the amount of time they’ spent taxi driving.
• Functional recovery after trauma 

  • After physical injury or trauma (like a stroke), unaffected areas of the brain are able to adapt and compensate for damaged areas
  • This functional recovery that may occur in the brain after trauma is an example of plasticity
  • Neuroscientists find that this can happen very quickly (spontaneous recovery) but then begins to slow down
• Functional recovery after trauma

  Regenerative developments in brain function arise from the brain’s plasticity, its ability to change structurally and functionally following trauma. 

  In plain english, the brain reorganises itself and finds new pathways to do things.

  One way in which it does this is by forming new synaptic connections near to the area of damage.
• Functional recovery after trauma

  Mechanisms for recovery

  So when brain cells are damaged, as they are during a stroke for example, other parts sometimes take over their functions. This occurs through what we refer to as neuronal unmasking

  = in which “inactive” synapses can be reactivated when they receive more neural input than they did previously.
• Functional recovery: Neuronal unmasking

  Wall (1977) first identified what he called ‘dormant synapses’ in the brain.

  These are synaptic connections that exist anatomically but their function is blocked. Under normal conditions these synapses may be ineffective because the rate of neural input to them is too low for them to be activated. 

  However, increasing the rate of input to these synapses, as would happen when a surrounding brain area becomes damaged, can then open (or ‘unmask’) these dormant synapses.
• The unmasking of dormant synapses can open connections to regions of the brain that are not normally activated, creating a lateral spread of activation which, in time, gives way to the development of new structures.
• Axonal sprouting is the growth of new nerve endings that connect other undamaged cells together. This forms new neural pathways that bypass the damaged areas
• Simply put, the existing blood vessels to an area change and redirect to support the new pathways

  OR new blood vessels form
• The use of similar areas on the opposite side of the brain to perform the function of the damaged area. 

  For example, say someone experiences damage to Broca’s area in the left hemisphere. The same region of the right hemisphere might take over this function for while.