Hemispheric Lateralisation and Split Brains

Question 1

What does hemispheric lateralisation mean?

Answer 1

The idea that a brain function is concentrated to one hemisphere.

Question 2

Language is lateralised to which hemisphere and to which regions?

Answer 2

The left hemisphere, in Broca and Wernicke’s areas.

Question 3

What is the left hemisphere also known as?

Answer 3

The analyser

Question 4

What is the right hemisphere also known as?

Answer 4

The synthesiser

Question 5

Drawing skills are lateralised to which hemisphere?

Answer 5

The right hemisphere.

Question 6

Describe the contralateral wiring in the motor area.

Answer 6

The left hemisphere controls muscle movement in the right side of the body.
The right hemisphere controls muscle movement in the left side of the body.

Question 7

Describe the contralateral wiring in the visual area.

Answer 7

Anything seen in the right visual field by both eyes is processed by the left hemisphere.
Anything seen in the left visual field by both eyes is processed by the right hemisphere.

Question 8

Name the psychologist who researched split brains.

Answer 8

Sperry

Question 9

What has happened to people with split brains and why?

Answer 9

People with split brains have had their corpus callosum severed, which connects both hemispheres.
This is done in people with epilepsy to reduce excessive electrical transmission between the 2 hemispheres, which reduces symptoms.

Question 10

Give the aim of Sperry’s research.

Answer 10

To understand how the two hemispheres work independently to deal with functions such as speech and vision.

Question 11

How many PPTs were studied in Sperry’s research?
What medical condition did they have?

Answer 11

11. They all had epilepsy.

Question 12

Name the piece of equipment used to study the PPTs.

Answer 12

Tachistoscope.

Question 13

Describe what happened in the procedure of the experiment.

Answer 13

The PPT is asked to focus on a cross in the centre of the screen. The LVF and RVF are shown 2 different images.

Question 14

What could PPTs do when a picture of an object was shown to the RVF?
Why?

Answer 14

The PPTs could describe what they saw as the LH contains the language centres.

Question 15

What did PPTs say when an object was shown to the LVF?
Why?

Answer 15

They said nothing was there.
The RH is unable to relay messages to the LH, therefore they are unable to describe it.

Question 16

Instead of verbally labelling objects in the LVF what could they do instead?

Answer 16

From a selection of items, they were able to select a matching object out of sight using their left hand.

Question 17

Explain the strength of there being a low risk of ethical issues when studying split brain patients.
Use the example that their brains were not split for the purpose of the research.
Use the counterpoint of lack of informed consent.
What did PPTs have to do for years after the study which could have been stressful?

Answer 17

The PPTs brains were already split before the study happened, meaning that PPTs brains were not harmed for the purpose of the research. On the other hand, the split-brain operation could have caused trauma for the patients, meaning they may not have fully understood what they had agreed to take part in. This means there are issues with informed consent. Additionally, PPTs were subjected to testing for many years after the study, which could have caused them stress.

Question 18

Explain the strength of there being research support to show that the 2 hemispheres process information differently.
Use the example of Fink and his PET scans to analyse how split brain patients processed the image of a forest.

Answer 18

Fink used PET scans to identify areas of the brain that become active during a visual processing task. When PPTs with connected brains were asked to look at a whole image (eg; an entire forest), regions of the RH were more active. When required to focus on the finer detail, (eg; specific trees) the LH became more active. This suggests that hemispheric lateralisation is a feature of connected and split brains.

Question 19

Explain the limitation of the LH analyser/RH synthesiser analogy being wrong. (Left/right brained people)
Use the example from Nielson who analysed over 1000 brains from people aged 7-29.

Answer 19

Research has shown that people do not have a dominant side to there brain. Nielson analysed brains from over 1000 people aged 7-29. He found that people used certain hemispheres some tasks, which provides evidence for lateralisation, but found no evidence of a dominant side. This means that idea of left/right brained people is wrong.

Question 19

Explain the limitation of confounding variables affecting split brain research.
Use the example of PPTs having epilepsy, but the control group not having it.

Answer 19

Sperry’s PPTs both had split brains and epilepsy, but his control group had neither. This means epilepsy acts as a CV, therefore any differences observed between the 2 groups may have been down to epilepsy rather than the split brain. This means that unique features of split brain PPTs cognition could have been due to epilepsy, not the split brain.