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Individual variability of higher brain functions

Richard E. Cytowic MD p00907 at psilink.com
Mon Nov 1 19:30:39 EST 1993

	There is rather a lot of inter-subject variability not only in 
gross brain anatomy, but in functional mapping (electrical). On the 
face of it, you propose to measure what cannot be measured.
	Variability in tertiary, and even secondary, gyration is evident 
to the naked eye. Most individuals in neuroscience, however, have 
little hands-on experience with autopsies and gross brain dissection.
	On the functional side, topographic mapping oflanguage cortex 
in an individual subject is much wider than that indicated in classical 
maps. Language is discretely localized within this zone, but with 
different sites VARIABLY committed to naming, stop consonants, etc. See 
Ojemann & Whitaker, Brain & language 6:239-260, and Whitaker & Ojemann 
Nature 270:50-51.  Additionally, there are GRADED effects within an 
area as small as 5 mm.
	Similar results were obtained with the ill-fated visual prosthesis 
project in the early 70s. Electrically stimulated phosphene maps were 
stable within subjects,but varied greatly between subjects -- and this 
in one of the cortical areas considered the most "hard wired."  (see 
dobelle & Mladejovsky Journal of physiology 243:553-576.
	A longer discussion of the above is found in Cytowic RE. 1989 
Synesthesia: A Union of the senses, pp 188-189, and 155-1660. Springer
	Whoever told you that movement and somesthesis are restricted 
to the pre-and post-central gyrii is misinformed. In 
marsupials (eg wallably and oppossum) there is CONSIDERABLE overlap of 
motor and sensory areas; overlap is also seen in cats and other 
mammals; multimodal neuron pools are found in humans too.
Richard E. Cytowic

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