Split-brain research into hemispheric lateralisation Flashcards
Define the term hemispheric lateralisation.
The idea that the two halves (hemispheres) of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other.
List the functions of the left hemisphere.
Sensory stimulus from right side of body Motor control of right side of body Speech, language and comprehension Analysis and calculations Time and sequencing Recognition of words, letters and numbers
List the functions of the right hemisphere.
Sensory stimulus from left side of body Motor control of left side of body Creativity Spatial ability Context/ perception Recognition of faces, places and objects
What does the information from the right visual field process to?
Left hemisphere
What is split-brain research?
A series of studies which began in the 1960s (and are still ongoing) involving epileptic patients who had experienced a surgical separation of the hemispheres of the brain. This allowed researchers to investigate the extent to which brain function is lateralised (as hemisphere can’t communicate with each other).
What’s an example of hemispheric lateralisation?
The ability to reproduce and understand language for most people is controlled by the left hemisphere.
What was the aim of Sperry and Gazzaniga (1968) natural experiment?
To investigate the effects commissurotomy (the severing of the corpus callosum) has to show that each hemisphere of the brain has different functions. Meaning that the researchers wanted to map lateralization of brain function and show that information in one side of the brain is inaccessible to the other side.
To investigate whether functions are lateralised
Describe Sperry’s split-brain study procedure.
An image was projected to an individual’s right visual field and the same or different image projected to the left. In the ‘normal’ brain the corpus callosum would share the information with both hemispheres so they can see but with a split-brain individual it meant the information couldn’t be conveyed to the other hemisphere.
State the describing what was seen findings.
Object shown right visual field - could easily describe what was seen.
Object shown left visual field - couldn’t describe what was seen, reporting that nothing was there.
Processed in right hemisphere - Lack of language centres.
In the normal brain, messages from right hemisphere would be relayed to language centres in the left hemisphere.
What did the recognition by touch (tactile) investigation with one hand involve?
Participants hands were hidden from their view behind the screen. They were asked to identify the object corresponding to what they saw on the screen.
An object was placed in one hand without the participant being able to see and then they were asked to identify what they were given.
What did the recognition by touch (tactile) investigation with both hands involve?
They were given two different objects one in each hand and then the objects were taken away.
They are then asked to find the objects, by touch, from a pile of items.
And were asked what they just held.
What were the findings of recognition by touch (tactile) investigation?
Could identify object placed in right hand
No conscious awareness placed in their left hand.
But they couldn’t find the object with the left hand in a bag full of objects.
When the objects were placed in one hand, the participants could point to what the object was with the same hand they held it with.
State the composite words findings.
Two words were presented simultaneously on either side of the visual fields.
For example, ‘key’ on the left and ‘ring’ on the right.
Key on left - individual selected it with left hand
Left visual field goes to right hemisphere linked to left hand
Right hemisphere - Recognition of faces, places and objects
Ring on right - Said the word
State the matching recognition findings.
Right hemisphere is dominant in recognising faces.
Were presented a picture made up of two different halves of a face.
Half man - right side. Half woman - left side.
What were the conclusions of Sperry’s split-brain study?
Supports the idea that the brain consists of two independent hemisphere they both have their own consciousness and that there’s no transfer between the two sides after a commissurotomy.
