localisation of function

• holistic theory of functions:

  • all parts of brain are involved in processing of thought and action
• localisation of functions:

  • different parts of brain perform different tasks
• hemispheres of brain:

  • cerebrum divided into 2 hemispheres
  • lateralisation = some of psych and physical functions are controlled or dominated by particular hemisphere
  • activity on left hand side of body is controlled by right hemisphere and vice versa (contralateral wiring)
• lobes of brain:

  • cerebral cortex is outer layer of both hemispheres
  • cortex at both hemispheres is subdivided into 4 lobes - each associated with different function
• frontal lobe:

  • decision making, personality, emotion
• motor cortex (both hemispheres): controls voluntary movements in opposite side of body
• somatosensory cortex (sensory cortex): where sensory info from skin is represented
• parietal lobe: spacial awareness
• occipital lobe: each eye sends info from right visual field to left visual cortex and vice versa

  • if left side is damaged both right visual fields= impaired
• auditory lobe: analyses speech based info

  • damage can lead to general hearing loss
• language centres:

  • restricted to left hemisphere
  • broca's area (frontal area) - responsible for speech production. damage caused leads to broca's aphasia (slow and laborious speech)
  • wernicke's area (temporal lobe) - responsible for speech comprehension. damaged caused leads to wernicke's aphasia (meaningless words)
• EVALUATION: neurosurgery evidence - linked to mental disorder

  • used for treating disorders by targeting specific areas
  • dougherty et al - 44 people with OCD had cingulotomy - post surgery follow up (32 weeks), 30% met criteria for successful response, 14% partial
  • successful procedures = behaviours associated with disorders are localised
• EVALUATION: evidence from brain scans

  • petersen et al - brain scans show wernicke's area active during listening task, brocas during reading
  • tulving et al - semantic and episodic memories in different parts of prefrontal cortex
  • confirms localised areas, objective methods used = scientific evidence that functions are localised
• EVALUATION: contradictory research evidence

  • lashley - removed areas of cortex (10-50%) in rats learning maze route
  • no area was more important in terms of ability to learn route - process of learning required every part of cortex
  • higher cognitive processes e.g learning aren't localised - distributed in holistic way
• EVALUATION: language localisation questioned

  • dick and tremblay - 2% of researchers think language is controlled only by broca and wernicke's area
  • brain imaging techniques - neural processes studied with more clarity - distributed more holistically than first thought
  • not confined to 2 areas, may be organised holistically - contradicts localisation theory