Hemispheric lateralisation and split-brain research
- Localisation refers to the fact that different areas of the brain are responsible for
different areas of the brain are responsible for different functions.
- Lateralisation refers to two sides of the brain.
Hemispheric lateralisation – brain is lateralised into two separate sides (hemispheres)
Left hemisphere (analyser) – language, maths, logic. (Language and speech) produce
speech. – controls movement on right side of body and RVF
Right hemisphere (synthesiser) – spatial abilities, face recognition, visual imagery, music.
(Visual motor tasks) – pick something up or draw. – controls movement on left side of
body and LVF
- Broca found that damage in one area of the left hemisphere resulted in language
deficits, whereas damage to the same area of the right brain hemisphere did not have
the same consequences.
Sperry 1968 (split brain research)
- Two hemispheres surgically separated by cutting the nerve connections that send info
form one hemisphere to another (corpus callosum)
- to treat epilepsy to reduce the electrical storm across hemispheres.
- Eleven split brain participants had an image of an object projected to RVF (processed by
LH), and same or different image would be projected to the LVF (processed by RH)
- Presenting the image to one hemisphere meant that info couldn’t be conveyed from that
hemisphere to the other.
Object shown to RVF:
- Participant can describe what is seen (language centres in LH)
Object shown to LVF:
- Cannot name object (no language centres in RH)
- Can select matching object behind screen using left hand.
- Can select object closely associated with picture of object using left hand.
- If a Pin up picture shown to LVF, participant giggled but reported seeing nothing or just a
flash of light.
Shows how certain functions are lateralised in the brain, show that LH is verbal, and the
RH is silent but emotional.
EVALUATION
- Localisation refers to the fact that different areas of the brain are responsible for
different areas of the brain are responsible for different functions.
- Lateralisation refers to two sides of the brain.
Hemispheric lateralisation – brain is lateralised into two separate sides (hemispheres)
Left hemisphere (analyser) – language, maths, logic. (Language and speech) produce
speech. – controls movement on right side of body and RVF
Right hemisphere (synthesiser) – spatial abilities, face recognition, visual imagery, music.
(Visual motor tasks) – pick something up or draw. – controls movement on left side of
body and LVF
- Broca found that damage in one area of the left hemisphere resulted in language
deficits, whereas damage to the same area of the right brain hemisphere did not have
the same consequences.
Sperry 1968 (split brain research)
- Two hemispheres surgically separated by cutting the nerve connections that send info
form one hemisphere to another (corpus callosum)
- to treat epilepsy to reduce the electrical storm across hemispheres.
- Eleven split brain participants had an image of an object projected to RVF (processed by
LH), and same or different image would be projected to the LVF (processed by RH)
- Presenting the image to one hemisphere meant that info couldn’t be conveyed from that
hemisphere to the other.
Object shown to RVF:
- Participant can describe what is seen (language centres in LH)
Object shown to LVF:
- Cannot name object (no language centres in RH)
- Can select matching object behind screen using left hand.
- Can select object closely associated with picture of object using left hand.
- If a Pin up picture shown to LVF, participant giggled but reported seeing nothing or just a
flash of light.
Shows how certain functions are lateralised in the brain, show that LH is verbal, and the
RH is silent but emotional.
EVALUATION
