Localisation

• Localisation theory


  Certain areas of the brain are responsible for certain processes, behaviours and activities

  
• Motor area


  Separated from the auditory area by the central suclus and found in the frontal lobe, this area is involved in regulating and coordinating movements

  
• Auditory area


  An area of the temporal lobe, located on the superior temporal gyrus, which is responsible for processing auditory information and speech
• Visual area


  An area in the occipital lobe which is responsible for processing visual information
• Somatosensory area


  An area of the parietal lobe which processes information associated with the senses e.g. touch, heat, pressure etc.
• Wernicke's Area


  Responsible for speech comprehension and located in the temporal lobe (the left temporal lobe for most people)
• Broca's Area


  Responsible for speech production and located in the frontal lobe, usually in the left hemisphere
• The left hemisphere of the brain is associated with language production and comprehension
• Supporting evidence for localisation of brain function

  • Tulving et al demonstrated, using PET scans, that semantic memories were recalled from the left prefrontal cortex, whilst episodic memories were recalled from the right prefrontal cortex
  • Petersen et al (1988) found that Wernicke's area activation is required for listening tasks, whereas Broca's area is required for reading tasks

  
• Supporting Case Studies


  • Phineas Gage was injured by a blasting rod which intersected the left side of his face, tearing through his prefrontal cortex
• The opposite to localisation theory would be a holistic view of brain function, suggesting that each function requires several brain areas to be activated and that these functions are not restricted to these areas

  
• Evidence supporting the link between certain brain areas and symptoms of OCD

  • Dougherty et al (2002) studied 44 OCD sufferers who'd undergone lesioning of the cingulate gyrus (cingulotomy) in order to control their symptoms

  
• Plasticity


  Refers to the brain's ability to physically and functionally adapt and change in response trauma, new experiences and learning
• The idea of plasticity opposes the previous theory that there is a 'critical window' for synaptic and neuronal connection formation, which occurred during the first 3 years of life, after which no new neuronal connections would be formed
• Synaptic pruning


  The process by which extra neurons and synaptic connections are eliminated in order to increase the efficiency of neuronal transmissions
• Evidence supporting the positive and negative effects of neuroplasticity

  • Ramachandran et al. has demonstrated negative plasticity through providing an explanation for phantom limb syndrome
  • The case study of Jodi Miller has demonstrated positive plasticity through recruiting homologous areas on the opposite side of the brain, axonal sprouting and the reformation of blood vessels

  
• Neuroplasticity occurs in animals too


  • Hubel and Weisel (1970) sutured the right eye of kittens, who are blind from birth, for a period of 6 months, opening the eyes and several points and monitoring brain activity in the visual cortex
• Neuroplasticity occurs in animals too
• Hubel and Weisel (1970) experiment

  1. Sutured the right eye of kittens who are blind from birth for 6 months

  2. Opened the eyes at several points

  3. Monitored brain activity in the visual cortex
• The researchers found that, although the right eye was closed, there was still activity in the left visual cortex, corresponding to the development of occular dominance columns

  
• During the period of high susceptibility in the fourth and fifth weeks, eye closure for as little as 3-4 days leads to a sharp decline in the number of cells that can be driven from both eyes
• This supports the idea that areas of the brain receiving no input can take over the function of highly stimulated areas, despite originally having different functions

  
• Cognitive reserve


  The level of education a person has attained and how long they have been in education
• Research suggests that an increased cognitive reserve increases the likelihood of making a disability-free recovery (DFR) after trauma, due to increased rates of neuroplasticity
• Schneider et al (2014) found that of the 769 patients studied, 214 achieved DFR after 1 year. Of those, 50.7% had between 12 and 15 years of previous education and 25.2% had more than 16 years
• This suggests that individuals who have been in education for a longer time may have developed the ability to form neuronal connections at a high rate, and therefore experience high levels of functional recovery, demonstrating positive plasticity

  
• Although after trauma the brain activates secondary neural circuits which contribute towards reinstating normal function (law of equipotentiality), the brain can only 'repair' itself up to a specific point, after which motor therapy or electrical stimulation is needed to increase recovery rates

  
• Lieperta et al (1998) found that after constraint-induced movement therapy, the motor performance of stroke patients improved significantly
• This suggests that functional recovery cannot be relied upon to reinstate normal function