Hemispheric L + Split brain Flashcards
What is hemispheric lateralisation?
The idea that the two halves (hemispheres) of the brain are functionally different and certain mental processes are mainly controlled by one hemisphere rather than the other, like language.
Why is language lateralised?
While language is localised- temporal and frontal lobe it is lateralised as it only appears in the left hemisphere therefore language is governed by the left side.
How is vision not fully lateralised?
It is both contralateral and ipsilateral (opposite and same sided). Each eye receives light through both fields the LVF of bth eyes is connected to RH and RVF connects to LH. Enabling vision to compare different perspectives
What is split brain research?
A series of studies beginning in the 1960’s involving epileptic people experiencing surgical separation of hemispheres of the brain reducing severity of epilepsy. Researchers could test lateral function of brain in isolation.
What does split brain involve?
Severing the connection between RH and LH, mainly the corpus callosum. The electrical activity in epilepsy now wont travel. However hemispheres are unable to communicate.
What was Sperry’s research aim and method?
Sperry 1968- Devised a system to study how two separated hemispheres deal with speech and vision.
11 people who had split brain were studies in a set up. Image was projected into RVF (processed by LH) and same or different would be projected into LVF (processed by RH). Information couldn’t be conveyed from one hem to another
Sperry’s findings and conclusion?
When picture of object was shown to RVF (LH) the participant could describe what was seen but they couldn’t if it was shown to the LVF they said nothing was there. This is because there is no way to relay the messages received by the RH to the language centres in LH. they could select a matching object using left hand. The observations show how certain functions are lateralised supporting the view that the LH is verbal and the RH is “silent” but emotional.
Evaluation of Lateralisation?
- Research showing that even in connected brains two hemispheres process info differently. Fink et al, used PET scans to identify which brain areas were active during a visual processing task. Looking at whole pic RH more active but details LH more active.
- LH as an analyser and RH as a synthesiser may be wrong. Despite lateralisation research shows people do not have dominant sides creating different personality. Nielson found people do use different sides but no evidence of dominant side.
Evaluation of split brain research?
- Evidence from more recent research Gazzaniga showed split brain actually perform better than connected controls on certain tasks. Faster at identifying the odd one out in a similar array of objects. Supporting distinct left brain and right brain.
- Casual relationships are hard to establish. The behaviour was compared to neurotypical control group. None had epilepsy major cofounding variable as it may be a result of epilepsy not split brain.
