lateralisation of the brain Flashcards
what is hesmipheric lateralistion??
Hemispheric Lateralisation: The dominance of one hemisphere of the brain for particular physical and psychological functions.
What does the left and right hemisphere focus on??
Overall, the left hemisphere appears to focus on detail and will be more active on tasks where an individual is asked to identify small details.
Conversely, the right hemisphere appears to process overall patterns and shows more activity when individuals are asked to make sense of e.g., a whole picture.
What are the two lateralised areas of the brain??
Broca’s
Wernicke’s
How was Broca area discovered
Broca, a French neurosurgeon, identified a ‘language centre’ .
This area is believed to be critical for speech production. Broca found that patients (firstly Patient Tan) with deficits who could understand language but could not speak or write had lesions in their left frontal hemisphere whereas patients with damage in these areas in the right hemisphere did not have the same language problems.
He studied patients which found that those with deficits in speech production had no issues of speech comprehension
He studied by post mortems
Where is Broca area
In the posterior of the left frontal lobe, situated next to motor cortex
What does the Broca area do
Helps coordinate speech production
What happens if it is damaged
Interestingly not all words are equally affected, nouns and verbs often seem to be fine. Conjunctions and prepositions have major problems. E.g. with Broca’s aphasia you couldn’t read ‘to be or not to be’ but could read ‘two bee ore knot two bee’.
Lesions in area can cause brocas aphasia causing difficulty in speech production
How was wernickes area discovered
Whereas Broca’s patients could understand language but not speak, patients with a lesion in the Wernicke’s area could speak but were unable to understand language. This is called Wernicke’s aphasia.
Where is wernickes area located
Wernicke’s area is in the posterior portion of the left temporal lobe.
What does wernickes area do
Wernicke proposed that language involves separate motor and sensory regions located in different cortical regions
. The motor region, located in Broca’s area, is close to the area that controls the mouth, tongue and vocal cords and hence is involved in speech production.
The sensory region, located in Wernicke’s area, is close to regions of the brain responsible for auditory and visual input. Input from these regions is thought to be transferred to
Wernicke’s area where it is recognised as language and associated with meaning.
What is the neural loop??
Broca’s area and Wernicke’s area work together to process and produce language.
There is a neural loop (called the arcuate fasciculus) running from Broca’s area (responsible for the production of language) and Wernicke’s area (responsible for the processing of spoken language).
Damage to both Broca’s and Wernicke’s areas may lead to global aphasia which is an inability to understand or to produce speech.
What are the strengths of hemispheric lateralisation??
- supporting research
P: There is research to support lateralisation. This is shown by Sperry’s pioneering split brain research.
E: Sperry found that the left hemisphere is more geared towards analytic and verbal tasks, whilst the right is more adept at performing spatial tasks and music.
E: This suggests that the two hemispheres do have seperate functions, with the left being the analyser whilst the right is the synthesiser.
L: This means that the corpus callosum is an important part of the brain that ties the 2 halves together, showing that the 2 hemispheres do communicate in everyday functioning.
What are the weaknesses of hemispheric lateralisation
- alternative explanation
- flawed methodology X2
What is the weaknesses of an alternative explanation??
P: The claim that functions are localised to certain areas of the brain has been criticised.
E: Lashley proposed the equipotentiality theory, which suggests that the basic motor and sensory functions are localised, but that higher mental functions are not.
E: He claimed that intact areas of the cortex could take over responsibility for specific cognitive functions following brain injury.
L:This therefore casts doubt on theories about the localisation of functions, suggesting that functions are not localised to just one region, as other regions can take over specific functions following brain injury.
What is the weakness of flawed methodology with research in wernickes and broca
P: Much of the research into Wernicke’s and Broca’s areas comes from case study evidence.
E: These studies involve individuals and investigate the effect of damage to their brain on their cognitive functions.
E: However, these effects may be specific to the individuals concerned and may not be generalisable to others. This is particularly true as the lateralisation of language areas to the left hemisphere is not universal.
L: This shows that we cannot use this explanation to explain all behaviour changes, BUT it is useful for understanding how each individual lesion affects behaviour.
