Hemispheric lateralisation Flashcards
The brain is contralateral (in most people)
The right hemisphere deals with the left side of the body and vice versa.
Left hemisphere
Language centres…
Broca’s area
Wernicke’s area
Focuses on detail
Right hemisphere
Facial recognition
Recognising emotion
Spatial relationships
Holistic processing
Recognises patterns
The two hemispheres are connected and able to communicate with one another via the
corpus callosum
what is the right hemisphere responsible for
responsible for recognising emotions in others.
what did Heller and Levy (1981) do
Heller and Levy (1981): a series of photographs of faces that had been split (one half was smiling, the other was neutral) were shown to participants.
After each pair of photographs had been shown, the participant was asked which they thought was happier.
Generally, the emotion displayed in the of the picture was the emotion recognised by the participant.
why did Heller and Levy (1981) find what they found
The right hemisphere is dominant for recognising emotion.
It is information presented to the left visual field (i.e. the left side of the photograph) which is processed by the right hemisphere.
The right hemisphere is also responsible for
spatial relationships and processing things holistically.
what did Fink, Halligan et al. (1996) do
When participants were asked to attend and name the stimulus at a local level (the small letters that make up the large letter), there was greater activity found in the left hemisphere.
When they were asked to attend and name the global attribute of the stimulus (the large letter, made up of small letters), thus processing the information holistically (as a whole), it prompted more activity in the right hemisphere.
what were the conclusions of Fink, Halligan et al. (1996) study
Conclusion: the left hemisphere is dominant for processing detail vs. the right hemisphere, which is dominant for holistic processing and pattern recognition.
Brain lateralisation increases neural processing capacity…
…because as one hemisphere engages in a particular task, this leaves the other hemisphere free to engage in another function.
This is supported by Rogers et al. (2004) who found that in the domestic chicken, brain lateralisation is associated with an enhanced ability to perform two tasks simultaneously - finding food and being vigilant for predators.
This study provides some evidence that brain lateralisation enhances brain efficiency in cognitive tasks that demand the simultaneous but different use of both hemispheres……there may be an evolutionary basis to this.
However, there is little empirical evidence to support this assertion.
Research has suggested that lateralisation of function appears not to stay the same throughout an individual’s lifetime, but changes with normal ageing.
Across many types of tasks and many brain areas, lateralised patterns found in younger individuals tend to switch to bilateral patterns in healthy older adults.
Bilateral patterns: involving both hemispheres i.e. neither hemisphere is dominant for the function.
Therefore, lateralisation of language function to the left hemisphere is not fixed, as the right hemisphere takes on more of this function with age.
This was supported by Szaflarski et al (2006), who found that language became more lateralised (dominant) to the left hemisphere with increasing age in children/adolescents.
BUT…after age 25, this trend reverses as lateralisation decreased with each decade of life, with signs of greater sharing of language function across the brain hemispheres in later life.
This therefore suggests that using the extra [cognitive] processing resources of the other hemisphere compensates for general age-related declines in function.
Research suggests that language may not be restricted to the left hemisphere.
Split-brain research suggests that the right hemisphere is unable to handle even rudimentary language processing and that damage to the left hemisphere was far more detrimental to language function than damage to the right hemisphere.
However, case study research challenges the idea that language is left-lateralised….
The case of E.B (Danelli et al., 2013) demonstrates the language capabilities of the right hemisphere. E.B.’s right hemisphere compensated for the loss of his left hemisphere in that he was found to be functioning linguistically well when tested at the age of 17 (having had his left hemisphere removed at 2½ years).
This therefore suggests that the right hemisphere is capable of processing language and developing that function when required.
However, E.B. did not fully recover all lost language functions (there were some subtle grammatical problems; difficulties picture-naming), which suggests that there is some lateralisation of language function in the left hemisphere.
