IUBio

interhemispheric interference

F. Frank LeFever flefever at ix.netcom.com
Sat Nov 14 23:26:56 EST 1998


In <MRp22.334$Ad4.4769 at news.eli.net> 73641.2531 at compuserve.com (Larry
Balog) writes: 
>
>Ned help finding more information about interhemispheric interference.
>I came across this topic while reading about split brains and the work
>of Michael Gazzaniga.  In one of his books he quoted work done by
>Richard Nakamura with monkeys.  Any help is appreciated.
>
>Larry Balog
>leader at ctaz.com
>
I can only guess that this refers to a phenomenon described by
Gazzaniga and others, in which (for example) the left hand (controlled
by the right hemisphere) begins some action--e.g. picking up a
newspaper--and the right hand (controlled by the left hemisphere) takes
the newspaper and puts it down.

I have seen a mild version of this in a patient with some frontal
damage and damage to the genu of the callosum, in which one hand
occasionally did things the patient ws embarassed to notice, e.g.
grabbing the necktie of the examiner--i.e., the Alien Hand Syndrome
(exetnsively studied by my friend, Victor Mark, q.v.).

However, in normal circumstances, the influence may be seen as
homeostatic--as for example, the discovery by Stanley Glick (an
undergrad student of mine MANY years prior) that when the callosum is
sectioned in rats a prior asymmetry in dopamine is exagerated, and an
asymmetry in ACh develops.  OR, it may be seen as "metacognitive", in
the sense of inhibiting the participation of one hemisphere when the
other hemisphere is better suited for the task.

If I remember correctly, Joseph LeDoux (when he was associated with
Gazzaniga, long before his work with the amygdala and emotional
conditioning) showed that a patient with the usual impaired
visual-spatial ability after right hemisphere lesion did OK if the
stimuli were restricted to the right visual field, thereby letting the
left hemisphere do what it could do--not as good as the right in the
right's normal condition, but better than the right in the right's
damaged condition.

I would interpret the failure of patients to use their left hemispheres
instead of the right for such tasks to persistence of what would have
been premorbidly OK, i.e. inhibition of left by right when doing
visual-spatial tasks.

It has been suggested that a similar persistent suppression of right by
left masks some language abilities of the right.  Aaron Smith claimed
(many years ago) that after left hemispherectomy the right hemisphere
was rather quickly capable of speech.

Sandra Witelson (whom I talked briefly with at Society for Neuroscience
last week) is a good author to search for neuropsychololgical work
regarding hemispheric relations and callosal differences (between males
and females, for ex.).  Also Jerre Levy?  Jacqueline Lieberman??

F. Frank LeFever, Ph.D.
New York Neuropsychology Group
In other (normal)



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