Sperry, Biological Area, Key region of the Brain

Question 1

Function of left hemisphere

Answer 1

• Receives information from the right side of the body (eg. right hand.)
• provides spoken language, so that they can say what they have seen.
• controls right hand
• receives info from right vision field

Question 2

Function of right hemisphere

Answer 2

• Receives information from the left side of the body
• Gets information from the left visual field
• predominantly controls emotions/artistic traits
• controls left hand

Question 3

Background generally of Sperry

Answer 3

That the brain is divided into two relatively symmetrical halves, left and right hemisphere.
- The two hemispheres are joined at the base by commissural fibres, which are bundled into different structures known as the corpus callosum.
- Each of the hemisphere has a different set of functions, which is referred to as ‘lateralisation of function.

Question 4

What notion did Broca and Wernicke’s area state?

Answer 4

• That certain brain areas have specific function is known as ‘localisation of function’.
• Broca’s specific area was speech production, and Wernicke’s area deals with the comprehension - they are both in the left hemisphere.

Question 5

What is the corpus callosum?

Answer 5

It is a bundle of thick nerve fibres which allow inter-hemispheric communication.

Question 6

What is a ‘Commissurotomy?

Answer 6

• It is a split brain operation.

Question 7

What did observers notice about split brain surgeries?

Answer 7

• Some observers noticed that if a patient had suffered damage to the pathways connecting the two hemispheres (corpus callosum), the frequency and the severity of the seizures were often reduced.

Question 8

How do epilepsies occur?

Answer 8

Epilepsy is a disorder of the brain characterised by excessive neutral activity leading to mental and motor dysfunction. they are caused by a sort of ‘electrical storm that spreads across the cortex, causing millions of neutrons to fire simultaneously.

Question 9

Aims of sperry’s study?

Answer 9

Sperry waned to make use of the opportunity presented by split brain patients to show that:
- Each hemisphere possesses an independent stream of conscious awareness
- Each hemisphere has its own separate chain of memories that are inaccessible to the others

Question 10

Research method? (pro and con.)

Answer 10

Quasi experiment, as there is a naturally occurring IV - whether you have a split brain or not.
Pro of Quasi: Can investigate IV’s that are unethical to manipulate.
Con: Cannot randomise -> individual differences such as could their brains be damaged due to epileptic seizures?

Question 11

Sperry’s sample used? (pro and con.)

Answer 11

11 patients.
- Had undergone split brain surgery.
- One male : had surgery over 5 and a half years before the study. One female had surgery more than 4 years before the study.

pro: large sample, considering the rarity of surgery and variety.
con: difference in surgery times -> affects rehabilitation and means different performance.

Question 12

Procedure? (Visual Tasks.)

Answer 12

• Sperry used a tachistoscope to present visual stimuli to the participants.
• The tachistoscope has a focal point in the middle and two areas where stimuli was presented. The participants using the tachistoscope would have one eye covered and were instructed to stare at the focal point.
• information presented to the left of the focal point would be seen in the left visual field which would then travel to the right hemisphere.
• Wearing an eye patch and staring at the focal point were controls. These controls ensure that stimuli was presented only to the desired visual field.

All visual stimuli was presented for only 0.1 seconds. This was another control as it is too quick for eye movements to cause visual information to enter both visual fields.

$/? Task. The $/? task had both a ‘$’ and a ‘?’ presented simultaneously (one to the right visual field and the other to the left visual field). Participants were then tested on the stimuli.

Question 13

Procedure? (Tactile tasks.)

Answer 13

In the tactile tests the participants would put their hands under the tachistoscope such that they could reach the objects.
- The participants’ hands were then covered. This was a control to ensure there was no visual stimuli going to either hemisphere and thus could not confound upon the results. Given that the tachistoscope was in between the participants and the objects, the participants could not see the objects. Again this was a control measure to ensure only tactile stimuli was introduced to the participants.

-Participants were introduced to objects by an experimenter, who placed them in the participants’ hands.

-Objects placed in the right hand of the participant are processed in the left hemisphere.

-Objects placed in the left hand of the participant are processed in the right hemisphere.

Question 14

Overall Sperry procedure summary?

Answer 14

Sperry devised a general procedure in which an image/word was projected to the right visual field(processed by the left hemisphere) or the left visual field(processed by the right hemisphere). Normally, the corpus callosum would share the info between both hemispheres giving them a complete picture of the visual world.

Question 15

Sperry conclusions?

Answer 15

• People with split brain have two separate visual inner worlds, each with its own train of visual images.
• they have a lack of cross integration, where each hemisphere does not know what the other is doing.
• They have two independent streams of consciousness, each with its own memories, perceptions etc.

Question 16

Sperry evaluations? (methodology.)

Answer 16

• LAB CONTROLLED CONDITIONS: High controls to reduce extraneous variables affecting the results. EG: words and images were only presented for 1/10 of a second to prevent participants moving their eyes to get the information into both hemispheres. This ensured that the tests revealed valid differences between hemispheres.

-LOW ECO. Validity: as conscious awareness is not usually measured in this way. PPts would not have images presented to the left or right visual field exclusively in the course of a normal day. This means that the results seen in the study would never be seen in day-to-day life.

• Ppts may respond to demand characteristics as they are aware they are taking part of in research.

Question 17

Sperry evaluation of Quasi experiments?

Answer 17

• Allows you to investigate behaviour of unique samples which otherwise would be unethical to manipulate.
• Due to naturally occurring IV it is impossible to know how individual differences could have affected the participants. Some may have had extensive brain damage due to epilepsy and some may have had very little.

Question 18

Sperry evaluation of data?

Answer 18

• Sperry collects in depth detailed information, such as participants being able to identify items presented to the left hemispheres via the right hand or right visual. Gives great deal of insight.
• Subjective data - cannot be compared objectively or used to compare against other research pieces.

Question 19

Internal validity in Sperry’s work?

Answer 19

• Due to high controls and nature of the procedure, it would have been possible to eliminate many extraneous variables - clarifies the reason for the performance on tactile and visual tasks.

Question 20

Reliability?

Answer 20

Due to the high controls of Sperry’s procedure and use of a techistope, it would be: easy to replicate and has been done and his results have been in general supported - would allow it to be tested for external reliability.

Question 21

Ethical considerations?

Answer 21

The study can be considered ethically sound as participants were fully aware of that they were taking part in tasks which separated the two hemispheres. Sperry had gained consent and ppts are not engaging in any activities that could cause them psychological harm/damage.

Question 22

Results that support Sperry’s conclusions?

Answer 22

1) Result: In the visual tasks, information shown and responded to in one visual field could only be recognised again if shown to the same visual field.–> Conclusion: People with split brains have two separate visual inner worlds, each with its own train of visual images.

2) In tactile tasks, objects felt by one hand were only recognised again by the same hand e.g objects first sensed by the right hand could not be retrieved by the left hand. —> Conclusion : Split brain patients have a lack of cross integration where the second hemisphere does not know what the first hemisphere has been doing.