sblack at UBISHOPS.CA (Stephen Black) writes:
>Actually, there's an obvious explanation for the larger size in the case
>of lefties. It may develop as a result of the greater traffic between the
>hemispheres, as motor control of the left hand is in the right hemisphere
>while the speech centre is (most often) in the left. In right-handers,
>both motor control and speech centre are in the same hemisphere.
IMHO, I don't think that explains anything -- after all, sinistrals and
dextrals use both hands. This explanation would hold only for tasks in which
the speech areas need to communicate with the dominant hand, and then only
for those parts of the corpus callosum involved in such a pathway.
>I recall that music is a right-hemisphere function (whatever that means)
>but it's unclear to me why that would predict greater cross-hemisphere
>traffic as in the case of left-handers. Perhaps the Neuropsychologia study
>which started all of this has the answer. I guess I'd better drop a note
>to my friendly interlibrary loan service.
We have to remember that any given task is likely to use processing areas
in both hemispheres, with interhemispheric interaction taking place at
several stages of processing, and via different parts of the callosum.
Looking for explanations in terms of simple dichotomies such as left- vs.
right-hemisphere function, handedness, and callosum size will only take us
so far.
Respectfully,
Kevin
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Kevin Spencer
Cognitive Psychophysiology Laboratory and Beckman Institute
University of Illinois at Urbana-Champaign
kspencer at p300.cpl.uiuc.edu
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