Localisation of function in the brain+ lateralisation and split-brain research Flashcards
(15 cards)
Localisation of function in the brain
-Localisation of function in the brain is the idea that specific areas of the brain are responsible for specific behaviours, processes, or activities
Hemispheric lateralisation
-Hemispheric lateralisation is the idea that some mental processes are mainly controlled by one hemisphere:
-The left side mainly controls language and logical tasks
-The right side mainly controls spatial ability, facial recognition, and emotions
Contralateral control
-Contralateral control is the idea that each hemisphere controls the opposite side of the body
Motor Cortex
-The motor cortex, located in the frontal lobe (both hemispheres), controls voluntary movements in the opposite side
Damage: damage to this area can result in loss of muscle function/paralysis on the opposite side to where the damage occurs
Visual Cortex
-The visual cortex, located in the occipital lobe (both hempspheres) processes visual information; both eyes send information to both hemispheres
-Damage: Damage to the occipital cortex could result in cortical blindness (complete blindness) or partial blindness (blindness in the opposite eye to where the damage occurred)
Somatosensory cortex
-Somatosensory cortex, located in the parietal lobe (both hemispheres) processes sensory information from the skin
-Damage: damage to the somatosensory cortex can results in loss of sensation and/or loss of ability to recognise objects through touch (agnosia)
-loss of sensation will occur in the opposite side to where the damage occurred due to lateralisation
Auditory cortex
-Auditory cortex, located in the temporal lobe (both hemispheres), processes auditory (sound)
-Damage: damage to the auditory cortex could lead to cortical deafness (complete deafness) however the structural integrity of the ear will remain the same
Broca’s area
-Broca’s area is located in the left frontal lobe
-Responsible for speech production
-Damage to this region leads to Broca’s aphasia; speech that is slow and lacks fluency, but comprehension of language is still intact
Wernicke’s area
-Wernicke’s area is located in the left temporal lobe
-Responsible for speech comprehension
-Damage to this region leads to Wernicke’s aphasia; speech is fluent but is meaningless; difficulty in understanding language
Split-brain research Sperry (1968)
-Sperry (1968) aimed to the investigate the extent of lateralisation with split-brain patients (people with a severed corpus callosum)
-PROCEDURE
-11 split-brain patients were placed in front of a screen in a lab setting
-They were presented with visual stimuli (words or images) to either their left visual field (processed by right hemisphere) or their right visual field (processed by left hemisphere) for less than a second
-As they had a severed corpus callosum, they were unable to pass information between hemispheres
-They were given a range of tasks including: verbal identification, object matching and drawing
FINDINGS
-It was found that when visual stimuli was presented to the right visual field (left hemisphere) patients were able to verbally identify the stimuli
-However, when the visual stimuli was presented to the left visual field (processed by the right hemisphere) they were unable to verbally identify the stimuli but were able to draw it or select it with their left hand
-This showed that the left hemisphere mainly controls language, whereas the right hemisphere mainly controls for spatial abilities
-This study supports the idea of brain lateralisation, as both hemispheres have specialised roles and can operate independently
All Advantages of Sperry (1968) research
-A strength of Sperry’s study is that the use of highly controlled lab procedures (e.g standardised presentation of the visual stimuli) increases the internal validity of the experiment and therefore increases the confidence that researchers have when establishing a cause-and-effect relationship
-Another strength of Sperry’s research is that it has real-world implications; the findings have contributed to our understanding of brain lateralisation and have had implications in treating brain disease and epilepsy
All limitations of Sperry (1968) research
-A limitation of Sperry’s research is that it uses a small sample of 11 patients, all of which have had surgery to remove their corpus callosum; this therefore limits the generalisability of results to people with normal brains
-Another limitation of Sperry’s research (procedure) is that the tasts used in the experiment (e.g flashing words on a screen for less than a second) are not typical of tasks that would be performed in everyday life and lack mundane realism, therefore reducing the ecological validity
Positive research support for lateralisation of function (Fink et al (1996))
-However, modern neuroimaging techniques provide evidence that some brain functions are lateralised even in people who have not undergone brain surgery
-Fink et al. (1996) found that when participants focused on an individual element of an image, there was more activation in their right hemisphere, and focusing on the entire image activated the left hemisphere
-This supports the idea that lateralisation of function is present in people with normal brains and not just split-brain patients
Positive support for localisation of function (Peterson et al. (1998)
neuroimaging techniques
-Modern neuroimaging techniques provide strong scientific evidence for localisation
-For example; Peterson et al. (1998) found that Broca’s area was activated during reading tasks and Wernicke’s area was active during listening tasks
-This objective and replicable studies support the idea that specific areas of the brain are responsible for specific behaviours/processes
Negative evaluation for localisation of function (Lashley (1950)) removing rats cortex
-Lashley (1950) removed 10-50% of rat’s cortex and found that no specific area was more important than another when learning how to navigate a maze; all learning abilities remained relatively unaffected
-This challenges the idea of strict localisation
