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Summary Sperry (1968) - hemisphere deconnection and unity in consciousness
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Sperry (1968): Hemisphere Deconnection and Unity inConsciousness
Epilepsy
Epileptic seizures are caused by a sort of electrical storm across the cortex, causing
many millions of neurones to fire.
In some patients, both hemispheres are involved, each amplifying the action of the
other and contributing to the seizure.
Severing the Corpus Callosum
If a patient had suffered damage to the corpus callosum, the frequency and severity
of their seizures was often reduced. This observation led to the split-brain operation
(hemispheric deconnection), a surgical procedure where the corpus callosum is
severed. By doing this, electrical signals being fired from the seizure in one
hemisphere could not pass over to the other hemisphere, reducing the severity.
Vogal and Bogen began a series of these operations involving 24 patients. The
medical benefits to the epilepsy were quite effective and the surgery did not appear
to have any noticeable effects on personality, measured intelligence, ability
conserve, perception, motor ability or coordination.
Sperry developed a split-brain operation for use on non-humans in the early 1950s
which allowed the testing of each hemisphere separately. He realised that such
testing in humans might provide the definitive answer as to whether there are any
differences between the abilities of the hemispheres. Sperry’s laboratory began
testing Vogel and Bogen’s patients.
Aim
To investigate the effects of hemisphere deconnection and to further understand the
functions of the left and right hemispheres.
Method
The study can be considered a quasi experiment.
The IV is naturally occurring – the presence or absence of a split brain.
The DV’s were whether the participant could name objects, recognise objects and
draw objects.
The study can also be considered a series of case studies as the research involved
intense study of 11 patients to investigate their behavioural symptoms.
Participants
The split-brain participants were 11 patients (male and female) who already had an
operation to disconnect their 2 hemispheres.
All participants had a history of severe epilepsy which had not responded to drug
therapy, and all were right-handed.
2 of the patients had been operated on some time before the experiments, the
remaining 9 had recently had the operation.
Procedure and Results
Sperry designed equipment that allowed information to be presented to just one
hemisphere. The participants’ vision was divided into left and right visual fields and
their hands were screened from their own view.
Participants had to remain in silence during the studies unless they were asked
questions. This was to prevent them passing information from the left side of the
brain to the right side.
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