Hemispheric Lateralisation
and Split Brain Research
LATERALISATION
The brain is split into two equal
symmetrical parts
Idea that the two halves
of the brain are
functionally different
and certain mental
processes are controlled
by one hemisphere
rather than the other.
The brain is contralateral
The left side of the body is controlled by
the right side of the brain and vice versa
LEFT HEMISPHERE
Language
Two main centres for language are only in the LH
Broca's area in the left frontal lobe
Wernicke's area in the left temporal lobe
If someone has a stroke on the left
side of their brain, the right side of the
body and speech is affected.
RIGHT HEMISPHERE
Dominant in recognising emotions in
others and spatial information
VISION
Both contralateral and ipsilateral
Each eye receives light from the left visual field
and the right visual field
LVF is connected to RH
RVF is connected to LH
AO3
Research shows that even in connected
brains the two hemispheres process
information differently
Gereon Fink et al (1996)
Used PET scans to identify which brain areas were active during a
visual processing task. When asked to attend to global elements of
an image the RH was more active.
When asked to point out finer details, LH dominated.
Idea of LH as the analyser and RH as synthesiser may be incorrect.
Nielsen et al (2013)
Analysed over 1000 brain scans
and found that people used certain
hemispheres for certain tasks, but
no evidence of a dominant side.
Localisation refers to the fact that some
functions are governed by specific areas
in the brain.
SPLIT BRAIN RESEARCH
Series of studies beginning in 1960 involving people with epilepsy who
had surgical separation of the hemispheres of their brain.
Sperry
(1968)
Devised a system to study how two separated hemispheres
deal with speech and vision
Eleven people with split brain operation studied with a special set up in which an image was projected.
Image projected to p. RVF.
In a normal brain, the corpus
callosum would share the
information across both
hemispheres giving a complete
picture
FINDINGS
When a picture was shown to RVF, the participant could describe
what was seen, but could not describe it if it was shown to the LVF.
This is because in the connected brain messages from the RH are relayed to the
language centres in LH. This is not possible in split brain.
Although they could not give verbal labels to objects in LVF, they
could select a matching object using their left hand
CONCLUSION
Observation showed how
certain functions are
lateralised in the brain and
support the view that the LH is
verbal and RH is silent but
emotional.
AO3
Support from recent research
Gazzaniga (1989) showed
that split brain participants
actually perform better on
certain tasks.
E.G Faster at identifying the odd one out of an array of similar objects.
LH cognitive strategies are not "watered down" by the RH
Casual relationships between the two are hard to
establish
Compared with a neurotypical control in original experiment, however none of
these people had epilepsy which caused a confounding variable.