Unit 2 - Classic Biological Core Studies Flashcards
Summarise the background of Sperry’s study
- brain has 2 symmetrical hemispheres, connected by the corpus callosum
- brain has contralateral control
- the brain has localized function = left side control speech and writing and the right side controls emotion and spatial awareness
- each eye has two contralateral visual fields
- a ‘commissurotomy’ can cure extreme epilepsy and limit side effects by reducing the electrical activity
What is contralateral control?
the opposite sides control
What is a commissurotomy?
a split-brain operation that cuts out the corpus callosum
What was Sperry’s aim?
To study the functions of separated and independent hemispheres and to map the lateralization of brain functions
What was Sperry’s sample?
11 split-brain patients - all had a commissurotomy - all had severe epilepsy with no drug response 2/11 had surgery a while before study 9/11 had surgery recently
What is this sampling method by Sperry?
Opportunistic
What is a unity of consciousness?
Where the corpus callosum is able to pass information across between the two hemispheres
What was the equipment Sperry used?
A tachistoscope
- screen in front of subject
- hands hidden
- unable to see tactile objects
What happened when Sperry presented an object in the right visual field?
- Info to left hemisphere - language
2. Able to see, identify and find with right hand
What happened when Sperry presented an object in the left visual field?
- Info to right hemisphere - spatial awareness
- Able to draw and find with left hand
- Unable to see and identify
What happened when Sperry presented an apple to the left and a key to the right visual fields?
- Apple to right hemisphere, key to left hemisphere
- Able to draw apple and identify/see key
- Unable to identify seen an apple
What happened when Sperry presented maths problems to left visual field?
- Info to right hemisphere - maths
2. Able to carry out maths problems
What happened when Sperry presented a nude picture to the left visual field?
- Info to right hemisphere - not language
- Able to laugh and react
- Unable to identify what seen
What happened when Sperry presented an object to the right hand?
- Info to left hemisphere - language and process
2. Able to identify and point with same hand
What happened when Sperry presented an object to left hand?
- Info to right hemisphere - spatial awareness
- Able to find with left hand
- Unable to have an conscious awareness of it
How did Sperry carry out the visual tasks for 1 eye?
- Cover one eye
- Look at central fixation point
- Image projected for 1/10 second
How did Sperry carry out the visual tasks for both eyes?
- Watch fixation point
2. Flash two images either side simultaneously for 1/10 second
How did Sperry carry out right hemisphere tests?
- LVF shown object on screen, pick out object from touch in an array
- LVF shown simple maths ie. sort objects by shape, size, texture with left hand
- LVF and RVF shown geometric shapes with nude in LVF and RH responds non-verbally
How did Sperry carry out the tactile tasks for 1 hand?
- Subjects hands hidden behind screen
- Find object responding to what saw
or - Object placed in hand
- Asked what given and/or asked to point to what given
How did Sperry carry out the tactile tasks for both hands?
- 2 objects given in each hand
- Find objects by touch from array
- Asked to say what held
What did Sperry conclude about his study?
- Supports that brain consists of 2 independent hemispheres, each with own consciousness
- Dominant side = left (speech)
What ethics did Sperry uphold?
conducted ethically
Did Sperry’s study have internal reliability?
highly controlled lab experiment
Did Sperry’s study have external reliability?
- quite small but general trends found
- some ‘outright exceptions’ challenge reliability
Did Sperry’s study have construct validity?
- understanding
- not looking at central point
- Brain surgery timing