Hemispheric lateralisation

• Brain is lateralised, meaning that the left and right hemispheres of the brain are specialised for different functions
• Localised: some functions localised and appear in both hemispheres, e.g auditory, visual, motor, somatosensory.
• Localised and lateralised: 2 main lang centres in LH (for most). Broca's area is left frontal lobe. Wernicke's area is left temporal lobe. RH produces rudimentary words, provides emotional context. LH may be analyser, RH synthesiser.
• Contralateral: cross wired.
• Contralateral and Ipsilateral: LVF of both eyes connected to the RH and RVF of both eyes connected to LH. Enables visual areas to compare slightly diff perspectives from each eye, aids depth perception. Same arrangement for auditory areas.
• ++Evidence of lateralised brain functions in 'normal' brains. PET scans show that when 'normal' participants attend to global elements of image, the RH is more active. When focused on finer detail, specific areas of LH tend to dominate (Fink et al. 1996). This suggests hemispheric lateralisation is a feature of the normal brain as well as the split-brain.
• --The idea of analyser versus synthesiser brain may be wrong. May be different functions in each hemisphere, but research suggests people do not have a dominant side. Nielsen et al. (2013) analysed 1000 brain scans, finding certain hemispheres were used for certain tasks but no dominance. Suggests notion of left/right brained people is wrong.
• --Plasticity may be more important, because it deals with a loss of lateralisation. Lateralisation is adaptive, enabling two tasks with greater efficiency. On the other hand, neural plasticity is also adaptive. After damage to the brain, language can 'switch sides' (Holland et al. 1996).