Lesson 7 - Hemispheric Lateralisation

Question 1

Functions are governed by one side of the brain

Answer 1

• Language centres lateralised to the left hemisphere
• Broca’s area damage = expressive aphasia
• Wernicke’s Area damage = receptive aphasia
• Right hemisphere is dominant for visuo-spatial functions

Question 2

Hemispheric Connection

Answer 2

• Connected by bundle of nerve fibres called Corpus Callosum

- Enables information to be communicated between the 2 hemispheres

Question 3

Evolutionary Perspective AO3

Answer 3

• Increases neural processing capacity, which is adaptive
• Through using 1 hemisphere to engage in a particular task it allows the other hemisphere free to engage in another function
• Rogers et al. 2004 - Found chickens had hemispheric lateralisation
• Allowed them to do 2 tasks at once
• Find food and be vigilant for predators at the same time

Question 4

Szaflarski et al (2006) Age AO3

Answer 4

• Lateralisation patterns shift with age

- Most tasks generally becoming less lateralised in healthy adulthood

Question 5

Turk et al 2002 - JW AO3

Answer 5

• Split brain patient
• Developed capacity to speak using his right hemisphere
• Result that JW could speak about information presented in either the left visual field or the right visual field
• Appears that language was not lateralised entirely to the left hemisphere

Question 6

Danelli et al 2013 - EB AO3

Answer 6

• If one hemisphere is damaged then the other undamaged regions of the opposite hemisphere can compensate
• EB lost almost all his left hemisphere at the age of 2 and a half due to a tumour
• Language appeared normal in everyday life in terms of vocab and grammar
• Systematic testing revealed subtle grammatical problems as well as poorer than normal scores on picture naming and reading of loan words
• Language function can be largely preserved after removal of the left hemisphere in childhood
• But it cannot be preserved with perfect mastery of each component of language

Question 7

Split-Brain Research

Answer 7

• Surgeons cut the corpus callosum to prevent violent electrical activity caused by epileptic seizures from one hemisphere to the other
• Patients were called split-brain patients

Question 8

Sperry and Gazzaniga (1968)

Answer 8

• Information from the left visual field goes into the right hemisphere and vice versa
• No way for info to travel from one hemisphere to the other

Question 9

Procedure

Answer 9

• Patients asked to stare at a dot in the centre of the screen
• Then information is presented in either left or right visual field
• Asked to make responses with either their left hand (right hemisphere) or their right hand (left hemisphere) or verbally (left hemisphere) without being able to see what their hands were doing

Question 10

Findings

Answer 10

• They may be flashed an image of a dog in their right visual field and then asked what they are seen
• They will answer dog because information will have gone into their left hemisphere where the language centres are
• If a picture of a cat is shown in their left visual field and they are asked what they have seen they will not be able to see because the info goes to the right hemisphere (no language centres)
• However, they can draw a picture of a cat with their left hand because the right hemisphere controls this hand

Question 11

Science AO3

Answer 11

Allowed for many discoveries of hemispheric lateralisation

Question 12

Laboratory AO3

Answer 12

Highly controlled and scientific

Question 13

Drug Therapy AO3

Answer 13

• Could have affected the way the brain works

- Meaning the findings of split-brain research cannot be generalised

Question 14

Small Sample Size AO3

Answer 14

Cannot generalise

Question 15

Artificial Research AO3

Answer 15

• In real life, there is unrestricted use of both visual fields
• Experiment therefore lacks ecological validity