Sperry Flashcards
Describe what brain localisation is
idea certain parts of brain have a specific function
Background - brain lateralisation
= left side of brain specialised for language and logic
= right side of brain specialised for perception and creativity
Background - split brain theory + hemispheric deconnection
R+L hemispheres are connected via corpus callosum which enables them to communicate with eachother
Hemispheric deconnection is when hemispheres have been disconnected
Define commissurotomy
Define contralateral control
Commissurtomy = cutting and seperating the right + left hemispheres > hemispheric deconnection
Contralateral control = movement on each side of the body is controlled by opposite side of the brain > visual pathways cross over
Aim of Sperry
To investigate the effects of hemispheric disconnection on perception and memory
Research method of Sperry
Laboratory/Quasi Experiment
IV = whether participants had split brain or not
- participants with split-brains had already undergone hemisphere disconnection to reduce severe epilepsy
DV = participants ability to perform a variety of visual and tactile tests
Why might sperry’s study be considered a collection of case studies
Case study = in-depth study of one person/small group of people
Sperry carried out a number of different experiments on 11 people
so considered this as it looked in-depth at this small group of people
Sample of sperry
11 patients who had already undergone commissurotomies to sperate r+l hemisphere to control their epilepsy
first patient (male) had surgery over 5 1/2 yrs before study was conducted
second patient (female) in 30s had surgery more than 4 yrs before study was conducted
Apparatus of Sperry
A tachistocope was used to present visual stimuli
slide so they couldnt see their hands
Controls in Sperry
Wearing an eye patch
- to ensure that stimuli was presented only to the desired visual field -LVF or RVF
visual stimuli presented either side of focal point for 0.1s
= to quick for eye movements to cause visual information to enter both VF
Procedure of Sperry
Participants gazed at focal point in middle of screen. slides were projected either side of focal point for 1/10 of a second using a tachistoscope. A number of experiments were carried out
Example 1 - visual stimulus was flashed to either to LVF or RVF and participants were asked to describe it - visual test
Example 2 - tactile test (touching)
participants was asked to say/write name of object they were holding
Example 3 - A word eg. HEART is flashed on screen. HE is on left side of screen and ART is on the right side. Asked to say name of word
Results of Sperry
EXAMPLE 1 - participants could only describe objects flashed to RVF
Why - objects flashed to RVF are processed by LH which is responsible for language, so they can describe it
EXAMPLE 2 - only objects held in right hand can be named (speech or writing)
Why - objects held in right hand processed by LH, which processes language so object can be named
EXAMPLE 3 - split-brain participants would say ‘ART’ as this portion of word was projected to the left hemisphere
Conclusions
People with split brans have two separate visual inner worlds, each with its own train of visual images
Split-brain patients have a lack of cross-integration where the second hemisphere doesn’t know what first hemisphere has been doing
Outline how info was presented to patients LVF
particpants with one eye-covered centred his gaze on focal point on a projection screen.
visual stimuli were then back-projected onto screen at 1/10 of a second to LVF
Assess generalisability of Sperry
split brain research hard to generalise to wider population
= most people don’t have a split-brain
Reliability of Sperry
high level of control + standardised procedure
eg. show images at 1/10th of a second + staring at focal point
= study has been replicated +similar results found
most recent split-brain research has contradicted earlier research. case studies have shown some people can use their RH for language
Application of Sperry
helped us better understand how damage to a particular hemisphere can affect brain-functioning
Validity of Sperry
lacks mundane realism
= people not usually asked to look at info with only one VF
=in every day life people with split-brains can use both eyes to process info
some patients had greater disconnection than others - hard to determine effects of lateralisation
Ethics of Sperry
no major ethical issues
argued researchers took advantage of potentially vulnerable people
Sperry & Reductionism
most tasks involve a mixture of left + right brain skills
eg. when we hear speech, we decode the meaning from words + emotional tone in the voice
Sperry and Quantitave+Qualitaitve data
quantitative
- whether participants could or couldn’t name an object
qualitative
eg. when participant were asked to verbally identify objects placed in their hand, researchers recorded comments eg “i can’t do anything with it”
Sperry relates to biological explanations
look at how brain, nervous system, neurotrasmitters, genes all influence a person’s behaviour
sperry split-brain study looked at how brain structure is linked to specifcally left + right hemispheres
investigated 11 split-brain patiens who had undergone commisurotomy for eplieply (procedure)
Sperry and Key Theme ‘Regions of the Brain’
Sperry sheds light on function of corpus callosum
shoes it is a communcation pathway between two hems
split brain participants didn’t peform same as normal control participants
also showed functions of LH and RH
Individual, socail and cultrual diversity
INDIVIDUAL = people with split-brains are different to normal people with intact corpus callosum
SOCIAL DIVERSITY - used m+f. females less brain lateralisation than males as more likely to use both L+RH
CULTRUAL DIVERSITY - conducted on english-speaking partipants
people from other culture eg. japanese have different lateralisation patterns
