Split-brain research Flashcards

1
Q

What is hemispheric lateralisation?

A

The idea that the two halves of the brain are functionally different and certain mental processes and behaviours are dominated by one hemisphere.

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2
Q

Which brain structure connects the left and right hemisphere?

A

The corpus callosum.

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3
Q

What was Sperry’s experimental group?

A

11 participants, all having had a commissurotomy due to epileptic history.

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4
Q

Which hemisphere is known as the major hemisphere?

A

Left hemisphere.

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5
Q

What is a commissurotomy?

A

A procedure where the corpus callosum is severed so the two hemispheres cannot communicate.

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6
Q

Why was it important that participants had received a commissurotomy?

A

Because they could see the extent to which the two hemispheres were specialised for certain functions and whether they performed independently of one another.

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7
Q

If an image is presented to the left visual field, where will it be processed?

A

Right hemisphere.

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8
Q

Why was a commissurotomy used on the participants?

A

They all had epileptic history and the procedure was designed to control the seizures.

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9
Q

Why is the right hemisphere known as the minor hemisphere?

A

It cannot process language independently.

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10
Q

Where would an image be presented if it was to be processed by the left hemisphere?

A

Right visual field.

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11
Q

What is the corpus callosum?

A

A bundle of fibres which connect the two hemispheres.

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12
Q

Where would an image be presented if it was to be processed by the right hemisphere?

A

Left visual field.

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13
Q

Why is the left hemisphere known as the major hemisphere?

A

It can process language independently.

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14
Q

If an image is presented to the right visual field, where will it be processed?

A

Left hemisphere.

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15
Q

Which hemisphere is known as the minor hemisphere?

A

Right hemisphere.

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16
Q

Who conducted the majority of the split-brain research, (and was consequently awarded a Nobel Prize in 1981)?

A

Roger Sperry et al. (1968).

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17
Q

During Sperry’s investigations, what would happen with a split-brain after seeing two seperate images?

A

The two hemispheres could not communicate and the information cannot be conveyed to the other hemisphere.

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18
Q

Sperry found which hemisphere was specialised for processing language?

A

Left.

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19
Q

What was the general procedure devised by Sperry?

A

An image or word is projected to the right visual field and another to the left visual field. There was a fixation point to make sure images were shown the the correct visual field and they were only shown for a short time.

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20
Q

During Sperry’s investigations, what would happen with a neurotypical brain after seeing two seperate images?

A

The two hemispheres would communicate through the corpus callosum to get a complete picture.

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21
Q

What is the name for the procedure which splits the corpus callosum?

A

Commissurotomy.

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22
Q

Sperry found which hemisphere was specialised for facial recognition?

A

Right.

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23
Q

Sperry found which hemisphere was specialised for viewing objects in the left visual field?

A

Right.

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24
Q

If an image is presented to which visual field will the participant be able to describe it in speech and writing?

A

Right visual field (as then processed by left hemisphere).

25
Q

Sperry found which hemisphere was specialised for viewing objects in the right visual field?

A

Left.

26
Q

How did Sperry ensure that participants only saw images in hte correct visual field?

A

The ptps focused on a fixation point and images were projected either side for 0.1 seconds, this meant both hemispheres could not focus on each image.

27
Q

Sperry found which hemisphere was specialised for drawing?

A

Right.

28
Q

If an image is presented to the left visual field, will split-brain participants be able to describe it in speech and writing?

A

No, as processed by the right hemisphere. Instead, they will say they have seen nothing.

29
Q

Sperry found which hemisphere was specialised for controlling the left side of the body?

A

Right.

30
Q

Sperry found which hemisphere was specialised for controlling the right side of the body?

A

Left.

31
Q

Why would the participant claim to have seen nothing when showed an image?

A

Because the information of the object cannot be transferred to the left hemisphere through the corpus callosum.

32
Q

If an object was shown to a participant to the left visual field, what would happen?

A

They would claim that they cannot see anything, however, they would be able to identify it with their left hand.

33
Q

Two different objects are displayed, one to each visual field (case for the left and key for the right). Participants with split-brains are asked to draw what they see with their left hand and say what they drew?

A

Participants drew what was on the left half of the screen (the case) because it was seen with the right hemisphere which controls the left hand. However, they would say that they drew the key as this is on the right half of the screen, this is because language uses the left hemisphere which say the key in the right visual field.

34
Q

If an image is presented to the right visual field, will split-brain participants be able to describe it in speech and writing?

A

Yes, as processed by the left hemisphere.

35
Q

Objects are placed in the right hand for identification by touch of the split-brain participants, what happens next?

A

They can say what the object is as right hand goes to the left hemisphere which controls language.

36
Q

What happens when two different objects are given the participant, one is placed in each hand and they are then hidden for retrieval in a pile of items.

A

Each hand will search for the item which it held, if it picks up the object from the other hand, it will be rejected.

37
Q

Which hemisphere is dominant for matching faces?

A

The right hemisphere.

38
Q

What happens when objects are placed in the left hand for identification by touch?

A

They cannot identify it as the left hand goes to the right hemisphere which cannot transfer information to the left hemisphere for language.

39
Q

How do we know which hemisphere is dominant for facial recognition?

A

When faces are shown to the LVF the information is sent to he RH and the correct picture is selected. However, when pictures are shown to the RVF information is sent to the LH and the correct picture is not selected.

40
Q

What happens when participants are shown a composite picture (half on left and half on right)?

A

Each hemisphere sees half a face, the face given to the RVF is transferred to the LH a verbal description can be given. The face shown to the LVF is transferred to the RH then the correct picture can be selected.

41
Q

How was the language capabilities of the right hemisphere demonstrated?

A

A picture of a wall clock would be shown to the minor hemisphere, the patient was able to pick out a wristwatch with the left hand, which is controlled by the left hemisphere.

42
Q

T / F:

There is no language capabilities of the right hemisphere.

A

False, it has a limited language processing ability.

43
Q

AO3 - Generalisability.

A

One problem with the split-brain studies is that generalisation is not possible, there was only a group size of 11 participants, and all of these had a history of epileptic seizures. This suggests their brains were not neuro-typical before they received their commissurotomy. It was also poor methodology as there was no control over the extent to which brain fibres were cut, and the control group was unsuitable.

44
Q

AO3 - Controlled methodology.

A

An advantage of his research is that Sperry’s procedure was closely controlled using standardised procedures to allow replication. Patients were given eye patches to make sure they only received information in one visual field, and images were flashed up for a very brief time (fractions of a second) to ensure there was no possibility of looking over and using the other visual field. This strengthens the internal validity of the studies as we can be surer that it is the independent variable affecting the dependent rather than any extraneous factors.

45
Q

AO3 - Evidence for lateralisation.

A

Sperry’s work into the lateralisation through split-brain studies was the first to discover that the left hemisphere is more responsible for verbal and analytical tasks, whereas the right hemisphere is better at spatial and musical tasks. This has strengthened the understanding of how the brain works and paved the way for future research using scientific brain scanning imagery.

46
Q

AO3 - Theoretical basis.

A

Sperry’s work prompted a theoretical and philosophical debate about the degree of communication between the two hemispheres in everyday functioning and the nature of consciousness. Pucetti (1977) suggested the two hemispheres are so functionally different that they represent a duality in the brain.

47
Q

AO3 - Overstated differences.

A

It has been said that Sperry’s work overemphasises the functional differences between the hemispheres. Modern neuroscientists would contend that the actual distinction is less clear-cut and more messy than this.

48
Q

T / F:

The right hemisphere has language capability based on the appearance of letters.

A

False - It has semantic language capability.

49
Q

T / F:
According to the work of Sperry, if we display an image to the LVF then participants will be able to name what they have seen.

A

False - If displayed to RVF then they can name it as it’s processed in the LH.

50
Q

T / F:

Sperry used a great control group.

A

False - The control group was unsuitable with no history of epilepsy.

51
Q

T / F:

Brain lateralisation is fixed throughout the life span.

A

False - Changes and decreases with age.

52
Q

T / F:

Circadian rhythms last more than a day.

A

False - They are entrained to fit into 24 hours. (can be longer if left without zeitgebers)

53
Q

T / F:

The sleep-wake cycle and core body temperature are both circadian rhythms.

A

True.

54
Q

T / F:

Light is an important exogenous zeitgeber which entrains our bodies into a 24 hour rhythm.

A

True.

55
Q

T / F:
Siffre spent 2 years in a cave in France which allowed his body clock to free run and he found it settled around 24 hours.

A

False - It settled closer to 25 hours and he was in the cave 2 months not years.

56
Q

T / F:

Endogenous pacemakers are the internal body clock and include features such as social cues.

A

False - Excludes social cues.

57
Q

T / F:

Understanding of the sleep-wake cycle is important for our understanding of shift work and jet lag.

A

True.

58
Q

T / F:
Folkard (1985) conducted a study where he sped up the clock to 22 hours to see if ptps could adjust. He found that exogenous zeitgebers (clock time) could not override the natural free running rhythm.

A

True.

59
Q

T / F:
Core body temperature varies by about 2 degrees a day. Recall of stories read to children was found to be better at 3pm compared to the story told at 9am.

A

True.