Sperry: Regions of the Brain (Biological) Flashcards
What theories was Sperry’s study based on?
-There is functional localisation in the brain as well as functional lateralisation as certain areas are only found in the left hemisphere of the brain (Broca’s and Wernike’s)
-The right hemisphere receives information from and are concerned with the activities of the left side of the body and vice versa
Why did Sperry choose split brain patients?
He believed that they would reveal the true nature of the two hemispheres as a surgery that splits the brain would mean the two sides work independently
What previous research had been done before Sperry’s study?
-Research using split brain animals showed numerous behavioural effects
-Other research by Sperry on both humans and monkeys who had undergone surgical section of the corpus callosum suggested the behavioural effects of this surgery may be less severe than other forms of cerebral surgery
-More recent research by Sperry showed a large number of behavioural effects that correlate directly with the loss of the neocortical commissures in man as well as animals.
What were the aims of Sperry’s study?
To show that each hemisphere possesses an independent stream of conscious awareness and has its own separate chain of memories that are inaccessible to the other.
What research method was used in Sperry’s study?
Quasi experiment because the IV (having a split brain or not) was not directly manipulated by the researchers. No actual control group was necessary for comparison as the abilities of the visual fields and hemispheres in non-split brain individuals were already known. Some argue that the study can be considered a collection of case studies
What was the sample for Sperry’s study?
-11 patients who had undergone an extensive mid-line section of the cerebral commissures to control severe epileptic convulsions
-The time the patients had had the surgery varied but went up to 5 and a half years.
What happened in the visual test of Sperry’s study?
-With one eye covered, the participant centred their gaze on a fixed point in the centre of a translucent screen
-Visual stimuli were arranged in a standard projection and were then back projected at 1 tenth of a second or less
-Everything projected to the left of the central meridian of the screen is passed via the left visual field to the right hemisphere and vice versa (regardless of which eye was used)
What happened in the tactile test of Sperry’s study?
- Below the translucent screen there was a gap so that participants could reach objects but not see their hands
-Objects were then placed in either the participant’s right/left hand or both
-Information about objects placed in the left hand is processed by the right hemisphere and vice versa
What was the name of the apparatus used in Sperry’s study?
A tachistoscope
What were the key findings from the visual tests in Sperry’s study?
-Information shown and responded to in one visual field could only be recognised again if shown to the same visual field
-Information presented to the RVF (LH system in a typical right handed person) could be described in speech and writing (with the right hand). If the same information is presented to the LVF (RH), the participant insisted they either couldn’t see anything or that there was only a flash of light on the left side. However, the participant could point with their left hand to a matching picture/object presented among a collection of pictures/objects
-If different figures were presented simultaneous to different visual fields, the participant could draw the figure from the LVF with the left hand but reported they had seen the other figure shown.
What were the key findings from tactile tests in Sperry’s study?
Objects placed in the right hand could be described in speech or writing. If the same objects were placed in the left hand participants could only make wild guesses and often seemed unaware they were holding anything
-Objects felt by one hand were only recognised again by the same hand
-When two objects were placed simultaneously in each hand and then hidden in a pile of objects, both hands selected their own objects and ignored the other hand’s object
What conclusions can be drawn from Sperry’s study?
-People with a split brain have two separate visual inner worlds, each with its own train of visual images
-Split brain patients have a lack of cross integration where the second hemisphere does not know what the first hemisphere has been doing
Split brain patients seem to have two independent streams of consciousness, each with its own memories, perceptions, and impulses
What are the strengths and weaknesses of the research method used in Sperry’s study?
It took place in a lab setting which meant that it was highly controlled so it had internal validity. The fact it was a quasi experiment meant the experimenters didn’t have to manipulate the IV as it was naturally occurring.
What are the strengths and weaknesses of the types of data collected in Sperry’s study?
Qualitative data which gave an in-detailed description of difficulties of the patients which enabled Sperry to map brain lateralisation. However, there were reported modifications and exceptions to the disconnection symptoms of the split brain patients. Therefore, it would have been more scientific and clear to have quantified results.
What ethical considerations are there for Sperry’s study?
It was ethical as the participants gave informed consent, no deception was used, and they were neither harmed nor unduly stressed by the experimental tests.
