Hempispheric Lateralisation and Split Brain Research Flashcards
localisation of brain areas refers to
fact some functions(e.g vision and language) governed by specific areas in brain
for some fucntions localised areas appear in
both hemispheres
in the case of vision teh visual area is in
left occipital lobe
right occipital lobe
in left and right hemi respectivley
In case of langauge how many centres are there
2
in case of lang main two centres are only in
the LH
Broca’s areas in the
left frontal lobe
wernickes areas in the
left temporal lobe
language is
lateralised
language is lateralised meaning
performed by one hemisphere rather than the other
the RH can only produce (language)
rudimentary words and phrases
(links to card 12)Eventhough RH can only produce rudimentaryt words and phrases what does it contribute
emotional context to wahts being said
(link to card 11) this has led to suggestion LH and RH are what
LH = analyser
RH = synthesiser
many functions arent
lateralised
many functions arent lateralised , give examples of function that appear in both hemispheres
vision
motor
somatosensory
areas
In the case of mototer area teh brain is
cross wired (contralateral wiring )
What does motor area in brain being cross wired (contralateral wiring ) mean
RH controls movement on the left side LH controls movement on the right side
int he case of vision how is the lateralisation ?
contralateral
ipsilateral
what does ipsilateral mean
opposite and same sided
in case of vision each eye recieves
light from left visual field
and right visual field
The LVF of both eyes connected to
RH
The RVF of both eyes connected to
LH
In the case of visual laterlisation this allows visual areas to
compare the slightly different perspective from each eye
and
aids depth perception
describe the arrangment for auditory input to auditory area
similar to visual
how does disparity from the two inputs helps us
locate source of sounds
A split brain operation involves
severing connections between RH &LH mainly the corpus callosum
what is the purpsoe of split brain reseearh
reduce epilepsy
what happens during an epileptic seizure
+ how do you reduce fits
brain xp excesive electrical activity which travels from one hemisphere to another
connections are cut, splitting the brain in two halves
split brian research studies how
hemispheres function when cant comm with each other
sperry devised system to study how
two seperated hemis deal with e.g speech and vision
PROCEDURE who was studied
11 people who had had split brain operation
PROCEDURE how were pt studied
using special set up in which
image could be projected to a pt RVF (processed by LH)
and same/ different image could be projected to LVF(processed by RH)
PROCEDURE In normal brain what would corpus callosum do
immediatley share info between both hemi giving a complete pic of visual world
PROCEDURE corpus callosum function in normal brain v split op pt means presenting image to one hemi of SBPT meant
info cannot be conveyed from that hemi to the other
FINDINGS When pic of object shown to pt RVF(linked to LH) what was happened
pt was able to describe waht was seen
but couldnt do this if object was shown to the LVF(RH) they said nothing was there
findings - when pic of object shown to pt rvf but then shown to lvf (rh) they said nothin was ther why was this
in the connected brain messages formt eh rh are relayed to teh laguage centres in the LH
but htis isnt possibel in the split brain
findigns - WHAT COULD PT NOT DO - ALTHOUGH THEY COULDNT DO THIS WHAT COULD THEY DO
give verbal labels to objects projected tot eh LVF
they could select a matchinng object out of sight using their left hand (linked to RH)
FINDINGS - the left hand was able to do hwat
select an object that was most closely associated with an object presented to the to the LVF
e.g ash tray selcted in repsosnes to pic of a cigarette
FINDINGS - if a pin up picture was shown to teh LVF what happened
there was an emotional reaction e.g gigle but the pt usually reported seeing nothing or just a flash of light
conclusions - what do the observations show
how certain functions are laterlaised in teh brain and support th eview the LH is verbal and the RH is silent but emotional
hemispehreic laterilisation eval points
research suppoert
limtation - one brain
split brain research eval poitns
research support
methodolgy highly controlled
coutnerpoitn - lack of eco validity
eval hemispheric - laterlisation in the connected brian
one strenght is x showing even in x brains the two hemisphere x info x
e.gx et al used x scans to identify which brain areas were x during a x processing task
when pt w x brains were asked to attend to x elemnts of the image such as looking at a pic of a x forest
x of the xx were much more x
when required to focus in on x detials such as x trees the speciic areas of the xx tended to x
this suggest that , at least as far as x processing is concerned, x laterlisation is a feature of the x brain as well as the x brain
one strenght is reseah showing even in connected brains the two hemisphere porcess info diffrently
e.g fink et al used PET scans to idenitfy which brain areas were active during a visual processing task
when pt w conne cted brains were asked to attend to gloabl elemnts of the image such as lookig at a pic of a whole forest
regions of the RH were much more active
when required to focus in on finer detials such as individual trees the speciic areas of the LH tended to dominate
this suggest that , at least as far as visual processing is concerned, hemispheric laterlisation is a feature of the connected brain as well as the split brain
limitaiton hemispheric - one brain
one limtiaiton is the idea that the LH as an x and RH as a x may be x
there may be x functions in the RH and LH but research sugeest people dont have a x side of their brain which creates a diff x
x et al analysed brain scans from over x people aged x-29 and did find that people used x hemispheres for x taks which is evidence for x
but there was x evidence of a x side i.e not an xbrian or a xbrain
this suggest the x of left or right x people is x
one limtiaiton is the idea that the LH as an anlyser and RH as a synthesiser may be wrong
there may be diff functions in the RH and LH but research sugeest people dont have a dominant side of their brain which creates a diff perosnality
nielsan et al analysed brain scans from over 1000 people aged 7-29 and did find that people used certian hemispheres for certain taks which is evidence for laterlisation
but there was no evidence of a dominant side i.e not an artists brian or a mathematicians brain
this suggest the notion of left or right brained people is wrong
eval split brian research - research support
One strength is that there is research to support the findings of split brain
research in x functioning brains. For example, x and x found that the left
hemisphere was more concerned with x and the x hemisphere is more concerned with x
and x functioning.
x (1986) reinforced this by stating that the right side of the brain is the
x side, whereas the left side of the brain was more x. This supports Sperry’s split-brain
research as it shows that the human brain is x , with each hemisphere having xfunctions.
One strength is that there is research to support the findings of split brain
research in ‘normal’ functioning brains. For example, Rasmussen and Milner (1977) found that the left
hemisphere was more concerned with language and the right hemisphere is more concerned with spatial
and artistic functioning. Ornstein (1986) reinforced this by stating that the right side of the brain is the
creative side, whereas the left side of the brain was more logical. This supports Sperry’s split-brain
research as it shows that the human brain is lateralised, with each hemisphere having different functions.
eval split brain research - methodology
A strength of split-brain research is the high levels of x used.
Sperry created a
very carefully x procedure. For example, to stop the natural x for participants to move
their eyes toward the x, the stimulus was only presented for around x milliseconds.
This ensured only the visual field aiming to be x actually saw the x , meaning only x hemisphere
was tested at a x.
This is a strength as it allowed Sperry to carry out a x range of variations of
the x procedure (such as testing x , x and x).
This has x our understanding of
x.
A strength of split-brain research is the high levels of control used.
Sperry created a
very carefully controlled procedure. For example, to stop the natural tendency for participants to move
their eyes toward the stimulus, the stimulus was only presented for around 200 milliseconds.
This ensured only the visual field aiming to be tested actually saw the stimulus, meaning only one hemisphere
was tested at a time.
This is a strength as it allowed Sperry to carry out a wide range of variations on
the original procedure (such as testing faces, words and touch).
This has extended our understanding on
lateralisation.
counterpoitn - lacks eco validity
a problem with lateralisation of function and split-brain research is the lack of x
validity. The tasks that the participants were given to do were very x . By Sperry x that
participants did not have enough time to x their eyes (and their visual field), this does not x how
the participants would use their x in x life. It is likely that they would use both x to try and
x for the cut corpus x. Therefore, it is x to make x of lateralisation
based on just the split brain x.
a problem with lateralisation of function and split-brain research is the lack of ecological
validity. The tasks that the participants were given to do were very controlled. By Sperry ensuring that
participants did not have enough time to move their eyes (and their visual field), this does not reflect how
the participants would use their brains in everyday life. It is likely that they would use both eyes to try and
compensate for the cut corpus callosum. Therefore, it is difficult to make generalisations of lateralisation
based on just the split brain research.
