Hack 69. Use Your Right Brainand Your Left, Too (4)
Like perceiving gender and moods, musical appreciation also appears to mostly involve right-brain-dominant processes (although, as we’ve seen, for keeping complex rhythms, the left brain is dominant).
Brain imaging studies have suggested that these kind of results can be understood by thinking of the hemispheres as specialized for different kinds of processing, not as specialized for processing different kinds of things. One study6 involved showing subjects letters made up of lots of little letters (e.g., the letter A made of up lots of little Ss). The left brain responded to the detail (the small letters) and the right brain to the global picture (the large letter constructed out of small letters). Subsequent work has shown that the story isn’t as clear as this study suggests. It seems you can get the left-detail/right-global pattern to reverse with the correct kinds of stimulus-task combinationbut it has confirmed that the hemispheric dominance is due to the demands of the task, not due to the nature of the information being processed.7 This gives some tentative legitimacy to the idea that there are left-brain and right-brain styles of processing.
But the important thing is how the two hemispheres combine, not how they perform in artificial situations like those of the split-brain patients. Brain imaging studies of normal people are based on the average results across many brains, and this tends to play down the large variation between different individuals in how the functions are distributed across the brain. Ultimately, however people’s brains are wired, they will be using both sides to deal with situations they encounterso it isn’t too helpful to become preoccupied with which half does what and whether they are processing with their left or their right.
6.9.3. End Notes
It was even claimed the two hemispheres of a patient’s split brain were conscious in different ways (http://www.macalester.edu/~psych/whathap/UBNRP/Split_Brain/Split_Brain_Consciousness.html).
Gazzaniga, M. S. (1998). The split brain revisited. Scientific American, 279(1), 50-55. (reprinted and updated 2002).
This demo is from the book The Lopsided Ape by Michael C. Corballis (Oxford University Press, paperback, 1991), p.267. Many thanks to Michael Parker (http://www.michaelparker.com) for bringing it to our attention.
At least we judge holistic features of faces (like gender or mood) by their left side, using our right hemisphere. Neuroimaging research shows left hemisphere involvement in analyzing the parts of faces. Rossion, B. et al. (2000). Hemispheric asymmetries for whole-based and part-based face processing in the human fusiform gyrus. Journal of Cognitive Neuroscience, 12, 793-802.
© Michael Burt, Perception Lab, http://perception.st-and.ac.uk.
Fink, G. R., Halligan, P. W., Marshall, J. C., et al. (1996). Where in the brain does visual attention select the forest and the trees? Nature 382 (6592), 626-628. There is a great discussion of this article by John McCrone in New Scientist (13 July 1999), reprinted online (http://web.archive.org/web/*/http://www.btinternet.com/~neuronaut/webtwo_features_leftbrain.html).
Stephan, K. E., Marshall, J. C., Friston, K. J., Rowe, J. B., Ritzl, A., Zilles, K., et al. (2003). Lateralized cognitive processes and lateralized task control in the human brain. Science, 301(5631), 384-386.
6.9.4. See Also
Other good starting points for reading about the neuroscience between the right and left brain story are ABC’s “All in the Mind” (http://www.abc.net.au/rn/science/mind/stories/s1137394.htm), “Hemispheres” at Neuroscience for Kids (http://faculty.washington.edu/chudler/split.html), and “New Theories of Expression Focus on Brain’s Two Sides,” article by Sandra Blakeslee (http://members.aol.com/sakrug/dualbrain.html; reprinted from the New York Times).
Taken from : Mind Hacks
