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Creado por Chloe Woods
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| Pregunta | Respuesta |
| Split-Brain Research into Hemispheric Lateralisation | Key Terms: Hemispheric Lateralisation: The idea that the two hemispheres of the brain are functionally different and that certain mental processes and behaviors are mainly controlled by one hemisphere, rather than the other, as in the example of language (which is also localised as well as lateralised) |
| Split-Brain Research into Hemispheric Lateralisation | Key Words Split-Brain research- A series of studies which began in the 1960's (and are still ongoing) involving epileptic patients who had experienced a surgical separation of the hemispheres of the brain. This allowed researchers to investigate the extent to which brain function is lateralised. |
| Split Brain Research: Hemispheric Lateralisation | Certain mental processes and behaviours are controlled or dominated by one hemisphere rather than the other (as in the example of language). Sperry and his colleges conducted a set of experiments to examine whether other neural processes are organised in this way as well (which he won the nobel prize for in 1981) |
| Split Brain Research: Split-brain studies | Sperry's experiments involved a unique group of individuals, all of whom had undergone the same surgical procedure called a commissurotomy in which the corpus callosum was cut in for patients with severe epilepsy, to control their seizures. This allowed researchers to investigate the extent to which brain function is lateralised. |
| Split Brain Research: Procedure | Image/word is projected to right visual field (RVF) or left visual field (LVF). In the 'normal' brain, the corpus callosum would immediately share the info between both hemispheres giving a complete picture of the visual world. However, presenting that image to one hemisphere of a split-brain patient meant that the info could not be conveyed. |
| Split-Brain Research: Key Findings, Describing what you see | Pictures shown to RVF could be described but not those to LVF, or it was reported as not there at all. So patients inability to describe objects in LVF was due to lack of language centers in the right hemisphere. |
| Split-Brain Research: Key Findings, Recognition by touch | Could not describe objects projected to LVF, but able to select a matching object from a selection of different objects using their left hand. The objects were behind a screen and in each case despite not being able to verbally identify what was seen, but nevertheless 'understand' what the object was using the right hemisphere and select the correct item accordingly. |
| Split-Brain Research: Key Findings, Composite Words | If two different words were presented simultaneously, one on either side of the visual fields (e.g key on the left and ring on the right), the patient would write with their left hand the word 'key' and say the word 'ring'. |
| Split-Brain Research: Key Findings, Matching faces | The right hemisphere also appears dominant in terms of recognising faces. When asked to match a face from a series of other faces, the picture processed by the right hemisphere was consistently selected, whilst the other image was frequently ignored. When a composite pic made up of 2 dif halves of a face was presented the left hemisphere dominated in terms of verbal description whereas the right hemisphere dominated in terms of selecting a matching picture. |
| Evaluation: Demonstrated Lateralised Brain Functions | Sperry's pioneering work into the split-brain phenomenon has produced a sizable and impressive body of research findings, the main conclusion of which appears to be that the LH appears to be more geared towards analytic and verbal tasks, whilst the RH is more adept at spatial tasks and music. The RH can only produce rudimentary words and phrases but contributes emotional and holistic content to language. |
| Evaluation: Strengths of the methodology | Made use of highly specialised and standardised procedures. Sperry's method of presenting visual info to one hemispheric field of vision at a time was quite ingenious. Typically patients would be asked to stare at a 'fixation point'. |
| Evaluation: Strengths of the methodology (continued) | The image would then be flashed up for 1/10 of a second, meaning the SB patient would not have time to move their eye across both sides of the VF. This allowed Sperry to vary aspects of the basic procedure and ensured that only one hemisphere was receiving info at a time. Thus he developed a very useful and well controlled procedure. |
| Evaluation: Theoretical Basis | Sperry's work prompted a theoretical and philosophical debate about the degree of communication between the two hemispheres in everyday functioning and the nature of consciousness. Some theorists, e.g. Pucetti, have suggested that the 2 hemispheres are so functionally different that they represent a form of duality in the brain - that in effect we are all two minds. In contrast other researchers have argued that, far from working in isolation, the 2 hemispheres form a highly integrated system and are both involved in most everyday tasks. |
| Evaluation: Issues with generalisation | Split-brain patients constitute an unusual sample of people. There were only 11 who took part in all variations of the basic procedure, all of whom had a collection of epileptic seizures. It has been argued that this may have cased unique changes in the brain that may have influenced the findings. The control group made up of 11 people with no history of epileptic seizures may have also been inappropriate. |
| Evaluation: Differences in function may be overstated | One legacy of Sperry's work is the growing body of pop-psychological literature that overemphasises and oversimplifies the functional distinction between the LH and the RH. Although the verbal and non-verbal labels can be applied to, on occasion, be usefully applied to summarise the differences between the two hemispheres, modern neuroscientists would contend that this is less clear-cut and much more messy than this. In the normal brain the 2 hemispheres are in constant communication when performing everyday tasks, and many of the behaviours typically associated with one hemisphere be effectively performed by the other when the situation requires it. |
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