Biological (CLASSIC) - regions of the brain - SPERRY Flashcards
describe the background of the study
brain is divided into two hemispheres, left and right
corpus callosum allows communication between the right and left hemisphere
left hemisphere: controls language and controls the right side of our body, receives info from right visual field
right hemisphere: controls emotions, artistic traits, controls left side of the body and receives info from left visual field
describe localisation of function
certain areas of the brain have specific functions
describe split brain operations
epileptic seizures are caused by an electrical storm that spreads across the cortex causing millions of neurons to fire simultaneously
if a patient suffered damage to pathways connecting the two hemispheres the frequency and severity of the seizures were often reduced
surgical procedure in which connecting tissue was cut - split brain operation
aims
- each hemisphere possesses an independent stream of conscious awareness
- each hemisphere has its own separate chain of memories that are inaccessible to the other
research method
quasi experiment as naturally occuring IV - split brain patients
DV - ability to perform on visual and tactile tasks and it was performed under controlled labatory conditions
collection of clinical case studies as small sample of 11 participants were studied in depth using extensive testing
sample
11 patients who had undergone split brain surgery
one male had surgery over 5 and 1/2 years before the study
one female had surgery more than 4 years before the study
9 others had surgery at varying times but not long before study was conducted
procedure - visual info
using a tachistoschope participant would look at fixation point on screen with one eye covered
visual stimulus presented to either right/left visual field
flashed for 0.1 second preventing participants moving their eyes and seeing stimulus with both eyes
-info (image/word) presented to one visual field, left/right
-info (image/word) presented to both visual fields simultaneously both left and right
then asked if they could recognise what they had seen in speech and writing or recognise by pointing to a matching image/similar object from collection
procedure - tactile info
below screen there was large gap for participants to put their hands under but not see their hands
objects placed in either one or both hands
asked to find objects, describe in speech or point to objects
participants had to remain in silence
this prevented them passing info from one side of brain to other
info shown to one VF can only be recognised again by same VF - why?
If in same VF will go to same hemisphere if different VF will go to different hemisphere - each hemisphere is unaware of what each has seen
info presented to RVF could be described in speech and writing - why?
RVF goes to LH which has capacity for speech and language
RVF goes to LH which controls right hand
if same info is presented to LVF participants insisted they did not see anything so could not describe it in speech or writing - however they could point to a matching object or image with their left hand - why?
LVF goes to RH which doesn’t have capacity for language
LVF goes to RH which controls left hand
if infopresented simultaneously ‘$’ to RVF and ‘?’ to LVF participant could draw ‘?’ with their left hand but reported in speech they had seen ‘$’ - why?
’$’ goes to RVF which goes to LH which has capacity for speech
‘?’ goes to LVF which goes to RH which controls left hand so can draw
if item had been placed in participant’s right hand it could be identified in speech and writing - why?
right hand goes to LH - which has capacity for language
if same item had been placed in participant’s left hand it could not be described in speech but could be selected again by same hand - why?
left hand goes to RH - no language ability
same hand access same hemisphere
if two different objects were placed in each hand at same time and then removed and hidden for retrieval in a pile of other items, each hand was seen to hunt through the pile and searched out its own object. During the search, each hand was seen to explore, identify and reject the item the other hand was searching - why?
each hemisphere works independently so both hands work independently
each hand and hemisphere doesn’t know what the other is looking for so will pass objects on
results and conclusions
- in the visual tasks information shown and responded to in one visual field could only be recognised again if shown to the same visual field concluding that people with split brains have two separate visual inner worlds each with its own train of visual images
- in the tactile tasks objects felt by one hand were only recognised again by the same hand e.g objects first sensed by the right hand could not be retrieved by the left hand concluding that split brain patients have a lack of cross integration where the second hemisphere does not know what the first hemisphere has been doing
strength of labcontrolled condition
highcontrols to reduce chance of extraneous variables affecting results. For example images presented for 0.1 secs preventing participantsmoving their eyes to get info into both hemispheres. Ensured tests revealed valid differences between hemispheres
weakness of lab controlled condition
low ecological validity as conscious awareness is not usually measured in this way. Participants would not have had images presented to R/L VF exclusively in the course of a day. This means that the results in the study would never be seen in the day to day life of a split brain patient
strength of quasi experiment
allows you to investigate behaviour of unique samples which would otherwise be unethical to manipulate. Sperry could not perform a split brain operation simply to study the effects. The fact that they were available meant that Sperry could gain insight into the nature and functions of the brain
weakness quasi experiment
naturally occurring IV it is impossible to know how individual differences could have affected the participants. Some may have had extensive brain damage due to epilepsy and some may have had very little. Therefore we can’t be sure the deficits seen in the tasks were due to the split brain operation and not some other element of brain damage
strength of type of data collected
Sperry collected in depth detailed info such as participants being able to identify items presented tot he left hemisphere via the right hand or right visual. This gives a great detail of insight into the functions of the hemispheres
weakness of type of data collected
subjective data so cannot be compared objectively or used to compare against other research pieces
strength of sample
large sample given to nature of research and considering the rarity of such patients
weakness of sample
due to being a pre existing IV there is a risk of individual differences between participants in terms of pre existing brain damage these differences may have affected performance on the split brain tasks
comment on the ecological validity
in this study the findings would be unlikely to be found in real life as a person who has a split brain would still use both eyes to compensate for the loss of communication between the two hemispheres and would use both the left and right visual fields in each eye to pass info to both parts of the brain so there is low ecological validity
comment on the internal validity
high controls and nature of the study it would have been possible to eliminate many extraneous variables which would indicate that having a split brain would be the reason for the performance on the visual and tactile tasks so high in internal validity
comment on the reliability
high controls of his procedure and use of a tachistoscope it would be very easy to replicate and has been done and his results have been in general supported - this would allow it to be tested for external reliability
comment on the ethical considerations
study can be considered ethically sound as participants were fully aware they were taking part in tasks which separated the two hemispheres. Sperry had gained consent and participants are not engaging in any activities that would causes them psychological harm or damage
comment on the ethnocentrism
there is evidence for differences in lateralization of function in cultures using different languages. If some cultures are less lateralized in their speech patients who had a split brain surgery might produce rather different results. This would mean these results could only apply to cultures sharing the same lateralization patterns as those found in English speakers
comment on the practical applications
main finding would suggest that this type of brain surgery is not as debilitating as first thought - so patients are unlikely to suffer from noticeable cognitive effects, as in everyday life they can access both visual fields and both hands at the same time therefore information will be processed by both hemispheres. However it does suggest that there could be profound effects on speech if the left hemisphere was surgically operated on
