Split Brain Research

Question 1

What can cutting the connections between hemispheres tell us?

Answer 1

Can tell us about hemispheric lateralisation.

It can be useful in understanding the role of each hemisphere and the extent to which functions are lateralised.

We can investigate which activities and behaviours are dominated or controlled by one hemisphere or the other.​

Split brain research began to take place in the 1960’s (is still ongoing) on epileptic patients who had experienced surgical separation of the hemispheres.

Question 1

Name something lateralised to the left hemisphere, and something lateralised to the right hemisphere.

Answer 1

E.g. speech production lateralised to the left.

E.g. voluntary movement of the left, is lateralised to the right.

Question 2

What is a commissurotomy?

Answer 2

The severing of the corpus callosum. ​

Question 3

What is a hemispherectomy?

Answer 3

A very rare neurosurgical procedure in which a cerebral hemisphere (half of the brain) is removed, disconnected, or disabled.

Question 4

Why would the corpus callosum need to be severed? Why is this?

Answer 4

Reduce the symptoms of epilepsy.

In epilepsy, one hemisphere of the brain is usually responsible.

Question 5

What happens when an epileptic episode occurs? Why does the severing of the corpus callosum work?

Answer 5

An electrical storm in one hemisphere of the brain, which then travels across the corpus callosum, causing the entire brain to be affected and then a blackout occurs.

By severing the corpus callosum this travelling of the electrical storm cannot occur and thus blackout and epileptic seizures cease/are reduced in severity.

Question 6

What were the aims of Sperry’s study in 1968?

Answer 6

To investigate the extent to which the two hemispheres were specialised for certain functions, and whether the hemispheres performed tasks independently of one another.

Question 7

What was the procedure of Sperry’s study in 1968? How many procedures were there?

Answer 7

Compared split brain patients to others with no hemisphere separation. ​

There were 2 types of procedure.

Question 8

Outline the ‘visual task’ procedure of Sperry’s study in 1968?

Answer 8

A word or image is projected into the left or right visual field and patient will be asked about that stimuli. ​

Question 9

Outline the ‘tactile task’ procedure of Sperry’s study in 1968?

Answer 9

Touch with objects.

Carried out with the PP’s hands underneath a screen so the they couldn’t see what they were doing.

They had to use ‘feel’ only.

Question 10

What were the 4 categories of findings that Sperry found in his 1968 study?

Answer 10

Describing what they see.

Recognition by touch.

Drawings.

Composite words.

Question 11

What would happen in a split-brain patient if an object is presented to the left visual field and the patient is asked to pick the object up with their right hand? (Sperry, 1968).

Answer 11

They would be unable to select the object because it was seen by the right hemisphere and the right hand is controlled by the left hemisphere.

Question 12

What would happen in a split-brain patient if an object is placed in the left hand and the patient is asked to name it?

Answer 12

The patient could not describe what they felt and could only make a wild guess.

Question 13

What would happen in a split-brain patient if a word is presented to the right visual field and the patient is asked to name it?

Answer 13

They could easily describe what was seen.

Question 14

What would happen in a split-brain patient if an object is placed in the right hand and the patient is asked to find the object with the same hand?

Answer 14

The patient would easily relocate the object.

Question 15

What would happen in a split-brain patient if an object is placed in the left hand and the patient is asked to find the object with their right hand?

Answer 15

The patient would not be able to locate the object, only being able to make wild guesses.

Question 16

What would happen in a split-brain patient if two different objects are placed in the left hand (key) and the right hand (ring). The objects are then hidden within other objects and the patient is asked to find them?

Answer 16

The individual hands would find their respective object.

Question 17

What would happen in a split-brain patient if they were shown an object to the right visual field and asked to draw it with the left hand and then the right hand?

Answer 17

They would only be able to draw it with their right hand.

Question 18

What would happen in a split-brain patient if they were presented with two words ‘ball’ to the left visual field, and ‘pen’ to the right visual field. They are asked to name one and pick the other up?

Answer 18

The patient would name ‘pen’ and pick up ‘ball’.

Question 19

Outline the findings about ‘drawings’ that Sperry found in 1968.

Answer 19

A picture is shown to the left or right visual field and the patient is asked to draw it.​

The drawings were consistently better when drawn by the left hand (controlled by the right hemisphere)​.

This was despite the patients actually being right-handed.

Question 20

Outline the findings about ‘composite words’ that Sperry found in 1968. (Patient shown two different words simultaneously).

Answer 20

Describe the word presented in their right visual field, as this was processed by their left hemisphere.

Pick up the word presented in their left visual field, as this was processed by their right hemisphere.

Question 21

What do the ‘drawing’ finding from Sperry’s 1968 study suggest?

Answer 21

Suggests that the right hemisphere (and therefore left hand) was superior at drawing ability.

Question 22

What three things did Sperry conclude from his 1968 study?

Answer 22

In split-brain patients the hemispheres of the brain process information separately.

Hemispheres have differing functions (e.g language tasks left) supporting lateralisation. ​

Participants seem to have two separate streams of consciousness with their own memories and perceptions.

Question 23

What did Sperry win in 1981?

Answer 23

Sperry‘s award winning research won him the Nobel Prize in 1981​.

Question 24

Did Sperry manipulate variables? What did this do?

Answer 24

Sperry did not need to manipulate variables, rendering it much more ethical than studies which manipulate variables.

Question 25

Did Sperry’s study from 1968 have a control group?

Answer 25

No control group, Sperry did not use a control group, which makes it difficult to truly establish cause and effect.

Question 26

What type of sample was Sperry’s study from 1968? Why?

Answer 26

Opportunity sample

Sperry asked patients who had undergone a hemispheric disconnection and had the surgery more than 4 years prior to the study.

Question 27

How controlled was Sperry’s study from 1968? How? What did this strengthen?

Answer 27

Sperry’s procedure was closely controlled.

Patients were given eye patches, and images were flashed up for a very brief time, meaning there was no possibility of looking over and using the other visual field.

This strengthens the internal validity of the study.

Question 28

How many patients did Sperry use in his 1968 study? Was this a big sample?

Answer 28

11 split brain patients – small sample.

Question 29

In Sperry’s study from 1968, all PPs had a history of seizures and this may have caused unique changes in the brain that may have influenced the findings. What could Sperry have done instead to counter this?

Answer 29

Instead, they could have incorporated a control group made from split-brain patients that had not experienced seizures prior.

Question 30

What was the data like, produced from Sperry’s study from 1968? What does this link to?

Answer 30

The data was artificially produced as in real life a severed corpus callosum can be compensated for by the unrestricted use of two eyes.

This can be linked to mundane realism.

Question 31

What did Sperry and Gazzaniga’s research yield? What did this show?

Answer 31

Sperry (and Gazzaniga’s) research has yielded a vast amount of further research.

Demonstrates that the left hemisphere is more geared towards analytic and verbal tasks whilst the right is more adept at performing spatial tasks, drawing ability and music.

Question 32

Outline the study from 2001 completed by Turk et al.

Answer 32

Discovered a patient who suffered damage to the left hemisphere but developed the capacity to speak in the right hemisphere, eventually leading to the ability to speak about the information presented to either side of the brain.

This suggests that perhaps lateralisation is not fixed and that the brain can adapt following damage to certain areas.​

Question 33

Outline the study from 1977 completed by Pucetti.

Answer 33

Suggested that the two hemispheres are so functionally different that they represent a form of duality in the brain. That, in effect, we are all two minds.

This is a situation that is only emphasised, rather than created, in the split-brain patient.

To contrast this, other researchers argue that our two hemispheres form a highly integrated system and are both involved in most everyday tasks and many of the behaviours typically associated with one hemisphere can be effectively performed by the other when the situation requires it.

Question 34

Outline Gazzaniga’s ‘interpreting emotions’ study from 1970.

Answer 34

A woman who had her corpus callosum severed was shown a picture of a nude woman in her left visual field. She giggled but could not explain why!​

When it was shown in her right visual field she was able to describe what she saw.

This is because the left hemisphere is responsible for language understanding and articulation, so she could describe what she saw.

When it was displayed in her left visual field, she reacted (giggled), as she understood the picture, but due to the lack of resources (all found in the left hemisphere) she was unable to describe it.

Question 35

Why did Gazzaniga conclude that his and Sperry’s assumptions that functions in the brain were lateralised was not quite as true as they first assumed?

Answer 35

Because of the vast (and every growing) body of evidence supporting cortical reorganisation.

Question 36

Who is Kim Peek?

Answer 36

Kim Peek was the inspiration for the 1988 Oscar-winning movie Rain Man.

Instead of the autism depicted in the film, Peek was born with severe brain damage including a total absence of a corpus callosum.

This meant that unlike Sperry’s participants, Peek’s split-brain was due to natural causes.

Question 37

Name 3 ‘specific talents’ that Kim Peek had?

Answer 37

He had word-for-word recall of over 12,000 books.

Could read two pages in around 10 seconds, employing his split-brain to simultaneously read one page with his right eye and one page with his left.

Knew phone books by heart.

Could say what day of the week a particular date fell on going back decades.

Could tell strangers the names of people who used to live next door to them years ago.

Question 38

What was Kim Peek’s IQ? Is this high?

Answer 38

Socially awkward with a low IQ of 87.

Question 39

What general ‘talent’ did Kim Peek have?

Answer 39

Peek’s powers of memory were prodigious.