Biopsychology - Brain Plasticity Flashcards
What are the key features of brain plasticity?
- The brain is ‘plastic’ - synaptic connections form and are pruned.
- The concept of plasticity is supported by studies.
- Plasticity is also supported by other research.
How are synaptic connections in the brain formed and pruned?
During infancy, the brain experiences a rapid growth in synaptic connections, peaking at around 15,000 at age 2-3 years (Gopnick et al. 1999).
As we age, rarely used connections are deleted and frequently used connections are strengthened - synaptic pruning.
It was once thought these changes were limited to childhood. But recent research suggests neural connections can change or be formed at any time, due to learning and experience.
What studies support the concept of plasticity? (Maguire)
Maguire et al. (2000) found significantly more volume of grey matter in the posterior hippocampus in London taxi drivers than in a matched control group. This part of the brain is linked with the development of spatial and navigational skills.
As part of their training, London cabbies take a complex test called ‘The Knowledge’ to assess their recall of city streets and possible routes. This learning experience appears to alter the structure of the taxi drivers’ brains. The longer they had been in the job, the more pronounced was the structural difference.
What other research supports plasticity? (Draganski)
Draganski et al. (2006) imaged the brains of medical students three months before and after final exams. Learning-induced changes were seen in the posterior hippocampus and the parietal cortex, presumably as a result of the exam.
What are the key features of functional recovery of the brain after trauma?
- Following trauma, unaffected areas of the brain take over lost functions.
- The brain ‘rewires’ itself by forming new synaptic connections.
- Structural changes in the brain (e.g. axonal sprouting).
How do unaffected areas of the brain take over lost functions?
Functional recovery of the brain after trauma is an important example of neural plasticity - healthy brain areas take over functions of areas damaged, destroyed, or even missing.
Neuroscientists suggest this process occurs quickly after trauma (spontaneous recovery) and then slows down - at which point the person may require rehabilitative therapy.
How does the brain rewire itself by forming new synaptic connections?
The brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of damage.
Secondary neural pathways that would not typically be used to carry out certain functions are activated or ‘unmasked’ to enable functioning to continue.
What structural changes are there to the brain?
Furthur structural changes may include:
- Axonal sprouting: growth of new nerve endings which connect with other undamaged cells to form new neuronal pathways.
- Reformation of blood vessels
- Recruitment of homologous (similar) areas on the opposite side of the brain to perform specific tasks.
What are the strengths of plasticity and functional recovery of the brain?
- practical application
- further support for neural plasticity from animal studies
What are the weaknesses of plasticity and functional recovery of the brain?
- potential negative consequences
- the relationship between age and plasticity is complex
- neural plasticity may be related to cognitive reserve
What practical applications are there to plasticity and recovery research?
Understanding processes involved in plasticity has contributed to the field of neurorehabilitation.
Techniques include movement therapy and electrical stimulation of the brain to counter deficits to cognitive functioning experienced following a stroke.
This shows that although the brain may have the capacity to ‘fix itself’ to a point, this process requires further intervention if it is to be successful.
What further support is there for neural plasticity from animal studies?
Hubel and Wiesel (1963) sewed one eye of a kitten shut and analysed the brains cortical responses.
The area of the visual cortex associated with the shut eye was not idle but continued to process information from the open eye.
This pioneering study demonstrates how loss of function leads to compensatory activity in the brain - evidence of neural plasticity.
What are the potential negative consequences of neural plasticity?
The brain’s ability to rewire itself can have maladaptive behavioural consequences. For example, prolonged drug use can result in poorer cognitive functioning and increased risk of dementia (Medina et al. 2007).
Also, 60-80% of amputees develop phantom limb syndrome - continued experience of sensations in the missing limb (as if it were still there), usually painful and thought to be due to reorganisation in the somatosensory cortex (Ramachandran and Hirstein 1998).
Such evidence suggests the structural and physical processes involved in functional recovery may not always be beneficial.
How is the relationship between age and plasticity complex?
Functional plasticity tends to reduce with age. The brain has a greater propensity for reorganisation in childhood as it constantly adapts to new experiences and learning.
However, Bezzola et al. (2012) demonstrated how 40 years of golf training produced changes in the neural representation of movement in participants aged 40-60.
This shows that neural plasticity does continue throughout our lifespan.
How may neural plasticity be related to cognitive reserve?
Evidence suggests a person’s educational attainment may influence how well the brain functionally adapts after injury.
Schneider et al. (2014) found the more time brain injury patients had spent in education (an indication of their cognitive reserve), the greater their chances of a disability-free recovery.
This suggests that cognitive reserve is a crucial factor in determining how well the brain adapts after trauma.
