13- Sperry: BIOLOGICAL Flashcards
Aim(s)
To investigate effects of hemisphere deconnection (in patients with severe epilepsy) and show that each hemisphere has different functions.
Design
-> Independent groups design.
-> Quasi experiment
-> Case study method also used (in-depth investigations of the 11 deconnected Ps).
-> Tasks carried out in highly controlled lab conditions - highly standardised.
(Controlled observation &
Snapshot study)
IV
Presence or absence of split brain
DV
Performance on tasks
Hypothesis
Split brain patients preform differently from without split brain
Study type
Series of
Clinical case studies
Sample
11 split brain
11 non split brain
Opportunity sample - refered to White Memorial Centre in Los Angeles USA
Materials
Tachistoscope
Procedure
(Summary version)
Screen
Focus’s on middle
Eye covered
Images flashed 0.1 second
Tasks done
Procedure
(Full / detailed version)
1) Ps are seated in front of the screen and asked to focus on a cross in the middle of the screen. One eye is covered.
2) Images are flashed on the screen. Each one is shown for a brief period of 0.1 second so that the eye only has time to process the image in the visual field where it is placed.
3) Tasks are designed to test how the right and left hemispheres respond to input from left visual field (LVF) and right visual field (RVF), and left and right hand.
TASKS USED TO TEST ABILITIES:
4) Visual and verbal task:
Ps are shown one image to the LVF and a different image to the RVF. They are asked to say what they see on the screen or to write what they see.
5) Visual material shown to one visual field only:
Material to RVF only is connected to left hemisphere so should be able to say what is there (because the language centre of the brain is in the left hemisphere). Material to LVF does not link to the language centre.
6) Visual and tactile task:
Ps are also asked to select an object from below the screen to match what they see.
7) Dual processing tactile task:
(2 tasks performed at the same time).
2 objects are placed simultaneously one in each hand and then hidden in a pile of objects. Each hand is required to recognise the objects.
8) Everyday life:
Ps are interviewed about everyday effects.
Results
1) Visual and verbal task, display $ sign to LVF and ? sign to RVF.
- Ps reports he saw the ? sign.
-> (shows RVF linked to LH where language centres reside). - Ps can draw $ sign with left hand.
-> (shows LF is linked to left hand and both linked to RH).
Why?
$ = LVF = RH = drawing, no language.
? = RVF = LH = Language.
Results
2) Visual material shown to one visual field only.
- Shown to RVF only:
Ps can describe visual material in speech and writing as normal.
-> (RVF linked to LH and right hand). - Shown to LVF only:
Ps reports he saw nothing or saw a flash of light on left. - Shown to LVF only:
Ps can select objects that are simular with left hand, e.g., select a wristwatch when shown a clock.
-> (Shows some language comprehension in RH). - Picture of a pretty women (a ‘pinup’) to LVF:
Ps giggles but says he saw nothing.
-> (Shows emotional response from RH).
Results
3) Visual and tactile task.
If an object is placed in the left hand Ps can only make wild guesses and may seem unaware that they are holding anything.
Results
4) Dual processing tactile task.
Ps’ right (or left) hand selects object presented to it, but each hand ignores the other hand’s objects.
Results
5) Everyday life.
Ps continue to watch TV or read books with no complaints; intellect and personality are unchanged. However, they have short-term memory deficits and difficulties with concentration.
