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.​

Question 2

When did split brain research begin?

Answer 2

The 1960’s.

It is still on going, taking place on epileptic patients who had experienced surgical separation of the hemispheres.

Question 3

Why are commissurotomies completed on those with epilepsy?

Answer 3

When an epileptic episode occurs, there is 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 4

What is a hemispherectomy?

Answer 4

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

Question 5

What was the aim of Sperry’s study?

(Sperry, 1968)

Answer 5

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 6

What was the procedure of Sperry’s study?

(Sperry, 1968)

Answer 6

Compared split brain patients to others with no hemisphere separation.

There were two procedures:

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

Tactile Tasks:
(Touch with objects) were carried out with the P’s hands underneath a screen so the PPs couldn’t see what they were doing. They had to use ‘feel’ only.​

Question 7

What were the findings of Sperry’s study?

(Sperry, 1968)

Answer 7

There were 4 different findings:

Describing what they see, (visual)
Recognition by touch, (tactile).
Drawings.
Composite words.

Question 8

What would a split brain patient do in this situation: ‘an object is placed in the left hand and the patient is asked to name it’.

(Tactile finding: Sperry)

Answer 8

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

Question 9

What would a split brain patient do in this situation: ‘an object is presented in the left visual field and the patient is asked to pick the object up with their right hand’.

(Tactile finding: Sperry)

Answer 9

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

Question 10

What would a split brain patient do in this situation: ‘a word is presented to the right visual❘ field and the patient is asked to name it’.

(Visual finding: Sperry)

Answer 10

They could easily describe what was seen.

Question 11

What would a split brain patient do in this situation: ‘an object is placed in the right hand and the patient is asked to find the object with the same hand’.

(Tactile finding: Sperry)

Answer 11

The patient would easily relocate the object.

Question 12

What would a split brain patient do in this situation: ‘an object is placed in the left hand and the patient is asked to find the object with the right hand’.

(Tactile finding: Sperry)

Answer 12

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

Question 13

What would a split brain patient do in this situation: ‘two different objects are place 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’.

(Tactile finding: Sperry)

Answer 13

The patient would be describe the key, as this object was processed by the left hemisphere.

They would be able to find the key, as it would have been processed by the right hemisphere.

Question 14

What would a split brain patient do in this situation: ‘a patient was shown an object to the left visual field and asked to draw it with the left hand and then the right hand’.

(Visual finding: Sperry)

Answer 14

The patient would draw the object better with their left hand, than their right hand.

Question 15

What would a split brain patient do in this situation: ‘two different words are shown to the left (ball) and the right (pen) visual field. They are asked to name one and pick the other up’.

(Tactile/ visual finding: Sperry)

Answer 15

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

Question 16

Outline drawing findings from Sperry’s study.

(Sperry, 1968)

Answer 16

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.

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

Question 17

Outline composite words findings from Sperry’s study.

(Sperry, 1968)

Answer 17

If a patient was shown two different words simultaneously they would:

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 18

What did Sperry conclude?

(Sperry, 1968)

Answer 18

It seems that in split-brain patients the hemispheres of the brain process information separately.

Hemispheres do have differing functions (e.g. language and analytical tasks left and drawing ability and spatial tasks right) supporting lateralisation. ​

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

Question 19

State 3 evaluative points from Sperry’s study.

(Sperry, 1968)

Answer 19

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

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

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

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

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.

11 split brain patients – small sample.

As all PPs had a history of seizures, this may have caused unique changes in the brain that may have influenced the findings. Instead, they could have incorporated a control group made from split-brain patients that had not experienced seizures prior.

The disconnection between the hemispheres was greater in some patients than others.

Some patients had experienced drug therapy for much longer than others​.

The comparison groups were not considered to be valid as they were often people with no history of epileptic seizures; instead they should have used patients who have experienced seizures

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.

Sperry (and Gazzaniga’s) research has yielded a vast amount of research that 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 20

Outline Gazzaniga’s study from 1970.

Answer 20

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 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 21

What did Sperry and Gazzaniga conclude about split-brain research?

Answer 21

Functions in the brain were lateralised was not quite as true as they first assumed, this is because of the vast (and every growing) body of evidence supporting cortical reorganisation.

Question 22

What is cortical reorganisation?

Answer 22

The brain’s ability to change its neural pathways and organization, adapting to new information, experiences, or injury.

Question 23

Outline Turk et al’s study from 2002.

(Supports the idea that brain hemisphere roles are not fixed)

Answer 23

Supports the idea that brain hemisphere roles are not fixed.

This is because they 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 24

Outline Pucetti’s study from 1977.

(Supports the idea of a split brain)

Answer 24

Supports the idea of a split brain.

This is because they stated 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.

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 25

Outline the case study of Kim Peek.

Answer 25

A natural split-brain.

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.

Although socially awkward with a low IQ of 87, Peek’s powers of memory were prodigious:

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

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

He knew phone books by heart, and could say what day of the week a particular date fell on going back decades.

His party trick was to tell strangers the names of people who used to live next door to them years ago.