Confabulation is a normal part of everyday life. As human beings we attempt to explain the world around us even if we have to make it up. Previous work by Wolford, Miller and Gazzaniga has demonstrated that the part of the mind responsible for making up such hypotheses, at least verbally, resides in the left hemisphere of the brain (2000). It is hypothesized to be in the frontal cortex, since this is an area “important for self generated behaviours” (Bower, 2000), but the actual area of the brain responsible has yet to be discovered. This paper suggests a theory for future experiments in an attempt to locate where in our brain these hypotheses stem from. This would be accomplished by having split brain patients perform a task which involves both pointing/choosing and verbally speaking during functional magnetic resonance imaging (fMRI) scans.
The idea for this paper stemmed from Gazzaniga’s work with split brain patients and modulation of the brain (1989). One task in particular seems as though it should be able to isolate what has become dubbed the left brain interpreter. This task was first performed in the mid-1970’s by a split patient known as P.S. and has since been replicated in many other patients. This task involves showing two images, one to each hemisphere, and then asking the participant to pick a picture from an array that was related to what they had just seen with each hand simultaneously. The experimenter then asks why they picked the specific pictures. The split brain participants will always answer by justifying both choices in terms of the original picture seen by the right eye only. The important part of this is that the left eye’s picture, which is interpreted by the right brain, never comes up in conversation. In P.S.’s case-
Dr. Gazzaniga and Dr. LeDoux showed P. S. a picture of a chicken claw in his right eye and a snow-covered house in the left eye. P. S. pointed to a chicken with his right hand and a snow shovel with his left.
"I'll never forget the day we got around to asking P. S., 'Why did you do that?' " said Dr. Gazzaniga. "He said, 'The chicken claw goes with the chicken.' That's all the left hemisphere saw. And then he looks at the shovel and said, 'The reason you need a shovel is to clean out the chicken shed.' “(Zimmer, 2005)
The moment P.S. explained the shovel he was using his left brain interpreter, since it has also been proven that the hands of split brain patients operate independently and without communication between the two hemispheres.
The left arm and eye are both connected to the right hemisphere, which is devoid of language. Split
This task would have to be modified using goggles in the fMRI that would separate the two hemispheres. The participant would then be showed the same array to each eye and asked to choose a picture with each hand that relates to what they just saw. The chosen pictures will then be shown to both hemispheres and the experimenter will inquire into reasons for the selection of each picture separately. This would allow the split brain participants to act as their own controls. When they explain their right hand’s choice it will be based purely on the connection to what the right eye, thus left brain, saw. When explaining the left hand’s selection the left brain is going to have to do some interpreting to come up with a reasonable story. It is at this point that we should see activation of the left brain interpreter. The order of the explanations can also be reversed to ensure that the sequence of explanations has no effect on what parts of the brain are activated.
There is one obvious problem that exists with this procedure- the participant must talk during the scan. The act of talking causes cranial movement which leads to images that are not clear enough to be used for study. However, there has recently been an fMRI study that has allowed participants to talk while still obtaining images with high enough resolution to obtain publishable results (Schlaggar et al. 2002). The experimenters limited the speech to single words, but with better technology we should eventually be able to correct for the movements caused by speaking in the images.
This author finds it interesting that the region(s) responsible for such a vital function of life has not been discovered. After all, one of the major differences between normal and abnormal people is the ability to confabulate correctly.[1] Finding out where these hypotheses/stories come from may help to further close the divide that exists between the brain and the mind.
- G. Wolford, M.B. Miller and M.S. Gazzaniga, The Journal of Neuroscience 20, 1
(2000) . - B. Bower, Science News 149, 124 (1996).
- M.S. Gazzaniga, Science 245, 947 (1989).
- C Zimmer, New York Times (2005) A Career Spent Learning How the Mind Emerges From the Brain
- B.L. Schlaggar, T.T. Brown, H.M. Lugar, K.M. Visscher, F.M. Miezin and S.E. Petersen, Science 296, 1476
[1] Correctly is, in this case, defined as believable to the general population and without the spontaneity seen in psychiatric patients.
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