hemispheric lateralization

    Cards (6)

    • Hemispheric lateralization:
      • The brain is lateralized i.e. two sides (hemispheres)
      Localized:
      • Some functions are localized and appear in both left and right hemispheres (LH and RH)
      • E.g. auditory, visual, motor, somatosensory areas
    • Localized and lateralized:
      • Two main language centres are in the LH (for most people) - Broca's area (left frontal lobe), Wernicke's area (left temporal lobe)
      • Right hemisphere produces rudimentary words but provides emotional context. Left hemisphere may be the analyzer, right hemisphere the synthesizer
    • Contralateral:
      • In the motor area, the right hemisphere controls the left side of the body and vice versa (cross-wired)
      Contralateral and ispilateral:
      • Left visual field (LVF) of both eyes is connected to the right hemisphere and right visual field (RVF) of both eyes is connected to the left hemisphere
      • Enables the visual areas to compare the slightly different perspective from each eye and aids depth perception
      • Same arrangement for auditory areas
    • One strength is evidence of lateralized brain functions in 'normal' brains
      • PET scans show when 'normal' ppts attend to global elements of an image, the right hemisphere is more active
      • When required to focus on finer detail the specific areas of the left hemisphere tend to dominate (Fink et al 1996)
      • This suggests that hemispheric lateralization is a feature of the normal brain as well as the split-brain
    • One limitation is the idea of analyzer versus synthesizer brain may be wrong
      • There may be different functions in the right hemisphere and left hemisphere but research suggests people do not have a dominant side, creating a different personality
      • Nielsen et al (2013) analyzed 1000 brain scans, finding people did use certain hemispheres for certain tasks but no dominance
      • This suggests that the notion of right- or left-brained people is wrong (e.g. 'artist' brain)
    • Evaluation extra: Lateralization versus plasticity
      • Lateralization is adaptive enabling two simultaneous tasks with greater efficiency, e.g. only lateralized chickens better at finding food while watching for predators (Rogers at al 2004)
      • On the other hand, neural plasticity is also adaptive. After damage to brain, language function can 'switch sides' (Holland et al 1996)
      • This seems to suggest that lateralization is first preference but ultimately plasticity is more important because it deals with loss of lateralization