Hemispheric Lateralisation and Split-brain Research Flashcards
(27 cards)
What does localisation refer to?
The fact that some functions (vision and language) are governed by very specific area in the brain.
What does it mean that the brain is lateralised?
There are two sides called hemispheres.
For some functions where do the localised areas appear?
In both hemispheres e.g. vision - the visual area is in the left and right occipital lobe which is located in the LH and RH respectively.
In the case of language where are the two main centres?
Only in the LH - Broca’s area in the left frontal lobe and Wernicke’s area in the left temporal lobe.
How is language lateralised?
Performed by one hemisphere (left) and not the other.
What can the RH only produce in regards to language?
Rudimentary words and phrases but it also contributes emotional context to what is being said - leading to the suggestion that the LH is the analyser and the RH is the synthesiser.
What is an example of a function that is not lateralised?
Vision.
How is vision not lateralised?
The motor and somatosensory areas appear in both hemispheres.
What is the motor area in the brain?
Cross-wired - RH controls movement on the left and LH controls movement on the right.
What is vision both?
Contralateral and ipsilateral - each eye receives light from the LVF and RVF.
The LVF of both eyes is connected to the RH and the RVF of both eyes is connected to the LH.
Enables visual areas to compare slightly different perspectives from each eye and aids depth and perception.
What does the disparity from the two inputs help us locate in regards to auditory input?
Locate the source of sounds.
Lateralisation evaluation: Research showing that even in connected brains two hemispheres process info differently.
One psychologist used PET scans to identify which brain areas were active during a visual processing task. When ppts with connected brains were asked to attend to global elements of an image regions of the RH were more active.
When focusing on a task with finer detail specific areas of the LH dominated.
Suggests hemispheric lateralisation is a feature of the connected brain as well as split-brain.
Lateralisation evaluation: the idea that the LH is the analyser and the RH is a synthesiser may be wrong.
Research suggests people don’t have a dominant side of their brain which creates a different personality.
One researcher analysed brain scans from over 1000 people 7-29 and found people used certain hemispheres for certain tasks but there was no evidence of a dominant side.
What does a ‘split-brain- operation involve?
Severing the connections between the RH and LH mainly the corpus collosum.
What does a split-brain operation reduce and how does it do it?
Reduces epilepsy - during an epileptic seizure the brain experiences excessive electrical activity which travels from one hemisphere to the other - to reduce fits the connections are cut by splitting the brain into two halves.
What do split-brain research study?
How the hemisphere functions when they can’t communicate with each other.
What did Sperry devise?
A system to study how two separated hemispheres deal with for example speech and vision.
Procedure of Sperry’s research
- 11 people who had a split-brain operation were studied.
- Used a set up where an image could be projected to a ppts RVF and the same, or different, image could be projected to the LVF.
In a normal brain what would the corpus callosum immediately do?
Share info between both hemispheres giving a complete picture of the visual world.
What happened when an image was presented to one hemisphere of a split-brain ppt?
The info couldn’t be conveyed from that hemisphere to the other.
What were the findings of Sperry’s study?
- When a picture of an object was shown to a ppts RVF the ppt could describe what was seen.
- But couldn’t do this if an object was shown to the LVF - said there was nothing there.
Why did ppts say there was nothing there if an image was shown to their LVF?
Because in the connected brain messages from the RH are relayed to the language centres in the LH however this isn’t possible in a split-brain
Even though ppts couldn’t give verbal labels to objects projected in the LVF what could they do?
Select a matching object that was closely associated with the object presented to the LVF.
What happened if a pinup picture was shown to the LVF?
There was an emotional response but ppts usually reported seeing nothing or just a flash of light.