Hemispheric Lateralisation and Split-Brain Research

Question 1

Outline Hemispheric Lateralisation

Answer 1

• Idea that certain functions are governed by one hemisphere of the brain
• Left hemisphere is responsible for right side of body
• Right hemisphere is responsible for left side of body

Question 2

Outline first experiment of Sperry’s split-brain research in investigating hemispheric lateralisation

Answer 2

• Describe what you see had 11 split brain patients who suffered from epilepsy and 11 non-epileptic control participants.
• Split visual field was set up with dot in centre asking them to focus on dot.
• Image presented on either side of visual field all participants asked to describe what they see.

Question 3

What were the findings of the describe what you see experiment

Answer 3

• Found that control participants could say what they saw regardless of what hemisphere processes that image
• Split-brain patients only say what they saw when image processed by left hemisphere, suggesting that the left hemisphere is responsible for speech production

Question 4

Outline second experiment of Sperry’s split-brain research in investigating hemispheric lateralisation

Answer 4

• Recognition by touch had 11 split brain patients who suffered from epilepsy and 11 non-epileptic control participants.
• Split visual field was set up with dot in centre asking them to focus on dot.
• Image presented on either side of visual field all participants asked to pick the object they see from a series of objects behind screen

Question 5

What were the findings of the recognition by touch experiment

Answer 5

• Found that control group could select the object by touch with either hand regardless of what hemisphere processed the image
• Split-brain patients could only select an object with the hand opposite to the hemisphere that processed the image, suggesting each hemisphere of brain is responsible for voluntary movement on opposite side of body.

Question 6

Outline the strength of split-brain research

Answer 6

• Procedures were standardised in laboratory experiments
• Presented with same stimuli and at same time
• Same standardised instructions (focus on dot in centre of screen to prevent eye movement)
• Easy to replicate and check reliability of findings
  -Adds appropriateness

Question 7

Outline one limitation of split-brain research

Answer 7

• Replications resulted in inconsistent findings
• Pinto did the same experiments and found that the split-brain patients had same findings as control group
  -Questions credibility
• However Pinto did experiments year after split brain surgery so original effects seen in Sperry’s experiments were only short-term until brain reorganised itself.
• Split-brain research only useful for investigating hemispheric lateralisation if conducted shortly after split-brain surgery

Question 8

Outline another limitation of split brain research

Answer 8

• Confounding variables such as drug therapy to treat epilepsy
• Split-brain patient’s unusual responses may be a result of the drug use rather than separate functioning of hemispheres.
• Questions credibility

Question 9

Outline final limitation of split brain research

Answer 9

• Suffers small sample sizes
• Sperry’s split brain research only involved 11 split brain patients
• Split brain procedure rarely used for treatments for epilepsy
• Limits generalisability and replicability of split brain research findings into hemispheric lateralisation
• Questions appropriateness

Question 10

What was right hemisphere found to specialise in

Answer 10

• Facial recognition
• Fusiform area responsible for facial recognition is larger in right hemisphere
• Inability to recognise familiar faces more often results from damage to right hemisphere

Question 11

Outline one strength of hemispheric lateralisation

Answer 11

• Supporting evidence from split brain research
• Describe what you see experiment and its findings
• Adds credibility

Question 12

Outline final strength of hemispheric lateralisation

Answer 12

• Further supporting evidence from split brain research
• Recognition by touch experiment and its findings
• Adds credibility

Question 13

Outline one limitation of hemispheric lateralisation

Answer 13

• Replications resulted in inconsistent findings
• Pinto did the same experiments and found that the split-brain patients had same findings as control group
  -Questions credibility
• However Pinto did experiments year after split brain surgery so original effects seen in Sperry’s experiments were only short-term until brain reorganised itself.
• Split-brain research only useful for investigating hemispheric lateralisation if conducted shortly after split-brain surgery

Question 14

Outline final limitation of hemispheric lateralisation

Answer 14

• Individual differences regarding which function is lateralised to which hemisphere
• Research found left handed people are more likely to have right hemisphere that specialises in language
• Lateralisation changes with age, most tasks become less lateralised in adulthood
• Suggests degree of flexibility in hemispheric lateralisation and questions credibility

Question 15

Which areas of the brain are contralateral (cause opposite side)

Answer 15

• Motor cortex (Movement)
• Somatosensory cortex (Touch sensations
• Visual cortex (Vision)
• Auditory cortex (Hearing)