Sperry

Question 1

Key theme

Answer 1

Regions of the brain

Question 2

contra-lateral control

Answer 2

Brain is split into 2 halves called hemispheres, left controls most of right hand side of body and right hemisphere controls most of left side.

Question 3

right hemisphere is in control of

Answer 3

spatial ability, face recognition, creativity, holistic thought, intuition, art and music

Question 4

left hemisphere is in control of

Answer 4

language, logical thought, understanding, analytic thought, science and math

Question 5

corpus callosum

Answer 5

wide, thick nerve track (bundle of nerve fibres) sits deep within brain and connects L and R hemispheres. Carries most of the communication between 2 halves of brain.

Question 6

Epilepsy

Answer 6

A condition that produces uncontrolled electrical discharges in the brain that spread causing disruption to brain functions. Attacks/ seizures can range from barely noticeable to those which cause tremors, collapsing and unconsciousness. Discharges start in one hemisphere and can spread across to the other making seizure more severe.

Question 7

Split brain/ hemisphere deconnection

Answer 7

To treat severe epilepsy, corpus callosum can be cut to disconnect left and right hemispheres to prevent spreading seizure from one hemisphere to other.
This operation involves splitting corpus callosum so the right and left hemisphere are no longer connected, so nothing will be able to pass from one hemisphere to other, therefore a fit won’t pass across, so severity is lessened. Operation only takes place is epilepsy is severe and patient doesn’t respond to drug therapy.

Question 8

Without corpus callosum…

Answer 8

the two hemispheres act independently like 2 separate brains instead of one whole brain.

Question 9

Theories on which study is based

Answer 9

Although L and R hemispheres are thought to have different responsibilities, the left is known to be responsible for language, logic problem solving, right is known to be responsible for creativity, spatial awareness and emotion. Left hemisphere controls right side of body and right controls left side.
Sperry believes studies involving split brain patients reveal the ‘true’ nature of the two hemispheres as a commissurotomy which disconnects the two hemispheres means they can only work independently.

Question 10

Background

Answer 10

Sperry was investigating regions of the brain and wanted to look at how the brain works and how different parts can influence behaviour. He wanted to investigate role of corpus callosum and find functions of L and R hemisphere. He based his experiment on a previous experiment by Vogal and Bogen- originally performed split of corpus callosum on people. (if had severe epilepsy and couldn’t respond to drug therapy)
Split did not cure epilepsy, just lessened fits severity.
Sperry wanted to know what patients could and could not do, tells roles of each hemisphere.
He investigated small number of people who previously had corpus callosum split.
In series of experiments, Sperry was able to demonstrate functions each hemisphere is responsible for.

Question 11

Aim

Answer 11

To investigate effects of hemisphere deconnection and to further understand functions of left and right hemispheres, wanted to see if people could still complete daily functions after having corpus callosum severed.

Question 12

Participants

Answer 12

-11 ps already had corpus callosum split.
-All had history of severe epilepsy that hadn’t responded to drug therapy.
-All right handed.
-2 ps had been successfully operated on sometime before experiments.
-9 ps had only recently undergone surgery.
-For most patients, operation reduced frequency and severity of their seizures.
-Opportunity sample of patients referred to the White Memorial Centre in LA, USA.
-Not generalisable.
-Not representative.

Question 13

Research method

Answer 13

-Quasi experiment; natural IV- ps already undergone surgery.
-not in ps own environment
-No control group
-Series of case studies; intensive study of 11ps to investigate their behavioural symptoms resulting from the surgery, they were case studies of the individuals which came from old lab experiments.

Question 14

strengths of quasi

Answer 14

-enables researchers to look at things not practical or ethical
-high ecological validity

Question 15

weaknesses of quasi

Answer 15

-hard to control extraneous variables
-hard to replicate

Question 16

strengths of case studies

Answer 16

-allow in depth background info
-carried out for rare cases where large samples not available

Question 17

weaknesses of case studies

Answer 17

-not generalisable
-not always scientific

Question 18

IV

Answer 18

Split brain or not

Question 19

DV

Answer 19

-ps performance on various visual and tactile tasks (naming objects, recognising objects, drawing objects)
-measuring cognition through test and case studies

Question 20

design

Answer 20

repeated measures- lowers individual differences.

Question 21

Materials/ apparatus

Answer 21

Patients abilities were tested suing a tachistoscope- device that displays images for a specific amount of time.
-in this case, visual stimuli were back projected onto screen at very high speed (0.1 seconds) so eye only has time to process image in visual field where it is placed.
Below screen was a gap so ps could reach various objects but could not see what their hands were doing.

Question 22

Stimuli were…

Answer 22

visual
tactual
auditory

Question 23

Extraneous variables controlled

Answer 23

By covering non tested eye presented stimulus Left visual field or Right visual field for limited time so 0.1s insufficient for eye to move to the other field.
They were shown object to other field after to see if they recognised the object.

Question 24

Procedure: presenting visual information

Answer 24

one eye covered, centred gaze on fixed point in centre of an upright translucent screen. Visual stimuli on 35mm transparencies were arranged in a standard projector and were then back-projected at 0.1s or less. ( too fast for eye movements to get info into wrong visual field).
-everything projected to left visual field would be received by right hemisphere.
-everything projected to right visual field would be received by left hemisphere.

Question 25

presenting visual information

Answer 25

A word flashed briefly to right field of view, patient was asked what they saw, because left hemisphere is dominant for verbal processing, patients answer MATCHES the word.
-when word flashed to left visual field and patient was asked what they saw, right hemisphere cannot share info with the left, so patient was UNABLE to SAY what they saw, but they could DRAW it.

Question 26

If patient presented with 2 WORDS on left and right of screen for less than 0.1s, ps should report…

Answer 26

Seeing the word on the RIGHT FIRST, because left hemisphere is responsible for language.
(RVF-left hemisphere)

Question 27

If patient presented with 2 PICTURES on left and right of screen for less than 0.1s, ps should report…

Answer 27

Seeing picture on the LEFT FIRST, right hemisphere is better at analysing pictures.
(LVF-right hemisphere)

Question 28

Procedure: presenting tactile information

Answer 28

-Below translucent screen there was a gap for ps to reach objects, but not see their hands.
-Objects were then places in either the ps right/left hand or both hands.
-Info about objects placed in right hand is processed by left hemisphere, and left hand processed by right hemisphere.
-Ps undertook a variety of both visual and tactile tests.
-Sperry also conducted variety of other tests which highlighted the lateralisation (i.e role of each hemisphere).

Question 29

Stereognostic test

Answer 29

discovering shape by touch

Question 30

presenting tactile info

Answer 30

-when ps asked to SAY or WRITE the word they were guessing the other side, so not saying keyring but keyhole, keylock etc…

Question 31

RESULTS- affects of hemisphere deconnection on ps

Answer 31

-hemisphere deconnection did NOT affect ps intelligence or personality.
-hemisphere deconnection DID affect ps in that they had; short term memory deficits, limited concentration spans, orientation problems.

Question 32

RESULTS- qualitative data

Answer 32

-Qualitative data was collected as behaviour and comments of ps were collected.
-when asked split brain patients to make spoken or written responses to objects in left hand, they would say things like “I can’t work with that hand” or “its numb” or “I don’t get any messages from that hand”.
-If they subsequently retrieve objects correctly, they had said they couldn’t feel, they said they were just guessing.

Question 33

RESULTS- visual tests

Answer 33

-info presented to RVF could be described in speech and writing (with right hand)
-if same info presented to LVF (right hemisphere) the ps insisted they did not see anything or that there was only a flash of light on left side (info could NOT be described in speech or writing)
-however, patient could point with left hand(right hemisphere) to matching picture presented among a collection of pictures.

Question 34

RESULTS-visual tests ($ and ?)

Answer 34

-if the $ was flashed to left visual field and a ? was shown to right visual field at the same time, ps could DRAW the $ with their left hand without looking (right hemisphere image processing)
-however, if asked what they had drawn, patient would say they had drawn ‘?’.
-When ps were flashed two words at same time, when asked to say the full word that they had seen, ps was only able to say one of the words. e.g ‘foot’ and ‘ball’ could only say ‘ball’.
-If word ‘foot ball’ was shown so ‘foot’ was left visual field, a foot could be DRAWN with left hand. Right visual field could see ‘ball’ so ps could SAY or WRITE that they had seen word ‘ball’.
-when picture of pretty woman (pinup) was shown to left visual field- ps giggled but said they saw nothing, shows emotional response from right visual field but they’re unaware of the arousal.

Question 35

RESULTS: tactile tests

Answer 35

-If object placed in right hand, can be SAID, WRITTEN or FOUND in a grab bag i.e when the pencil was placed among other objects with SAME HAND it has been placed in.
-When tactile stimulus was presented to LEFT hand; ps could NOT name it, able to DRAW with same hand, able to FIND again with same hand.
WHY?- because there is NO language centre in right hemisphere-unable to provide name- only right hemisphere has memory of object.
-Ps was able to verbally recall what they have in right hand, however, when same object placed in left hand, they guess what it is- only be able to pick it out of a grab bag to identify it.
-ps can retrieve an item from grab bag with SAME hand the item was ORIGINALLY placed in.

Question 36

CONCLUSIONS

Answer 36

-people with split brains have 2 separate visual inner worlds, each within its own train of visual images.
-split brain patients have lack of cross-integration where second hemisphere does not know what first hemisphere has been doing.
-split brain patients seem to have 2 independent streams of consciousness, each with its own memories, perceptions and impulses.
Sperry concluded: “when brain is disconnected we see two separate selves, each with its own memory and will.”

Question 37

How does Sperry link to key theme?

Answer 37

Regions of the brain looks at different parts of the brain and their functions, such as inferior frontal gyrus involved in cognitive control process, and ventral striatum which receives input from other brain regions.
Sperry was investigating effects of hemisphere de-connection on different tasks and wanted to understand functions of left and right hemispheres.
Ps took part in tests; visual tests, tactile tests, combination of visual and tactile and tests on right hemisphere.
Results showed that if an image is presented to right visual field, ps can name it, but if shown to left visual field then they cannot name it.
-determinism of biological assumptions on behaviour.

Question 38

localisation

Answer 38

brain functions of different areas.

Question 39

How does Sperry link to the biological area?

Answer 39

Biological approach attempts to explain behaviour through an understanding of biological and neurological processes. This approach assumes all behaviour has a biological basis, meaning all behaviour can be explained by our biology.
Sperry was investigating effects of hemisphere de-connection on different tasks and wanted to understand functions of left and right hemispheres.
Results from experiment show that language happens within the left hemisphere, so you can only describe an image if its presented to right visual field.
It also proved that the left hemisphere is more dominant.
He also proved separating the two hemispheres means they can no longer communicate with each other.