Is there a dominant ear???

F. Frank LeFever flefever at ix.netcom.com
Thu Sep 10 22:42:09 EST 1998


Nice to see undergraduates reinvent the wheel, but to get full benefit
of your exercise you should do some wider reading so as to fit your
findings into the greater scheme of things.

First, check out an experimental psych text or some such source re the
term "two point discrimination": this usuallly refers to two SPATIALLY
separated points.  In booth the visual and auditory modalities, you
have been looking at TEMPORAL discrimination.  A literature search in
this realm will pay big dividends.

Efron described this aspect of hemispheric specialization long ago (c.
30 years ago? I forget).  Later, Paula Tallal began a long and fruitful
research program exploring the implications of left hemisphere
proficiency in detecting very small temporal differences, involving
aphasia and also dyslexia.  She has an anatomical/neural functional
rationale.  Look for articles by her and collaborators, and follow the
trail of references in those articles.

You might also take a look at some neuropsychological texts or
handbooks.  The "dominant vs. nondominant" classification is obsolete. 
The relationship of haandedness to cerebral organization is complex and
subtle, and it is simply not true that the right hemisphere is overall
"dominant" for left-handers and the left for right-handers.  In
general, the left hemisphere is dominant for important language
functions in not only right-handers but also in the majority of
left-handers.  Paula suggests the temporal resolution abilities of the
left hemisphere underlie this.

re no difference between eyes: check out basic neuroanatomy, and note
that both eyes project to both hemispheres.  Try it again with light
limited to left or right visual FIELDS of both eyes.  (cf. split-brain
research, Roger Sperry; later, Michael Gazzaniga).

Yes, both ears eventually project to both hemispheres, but--!  Check
out literature on dichotic listening and ear extinction effects...

F. Frank LeFever, Ph.D.
New York Neuropsychology Group




In <35F7E6BE.C1A332B3 at writeme.com> Zoro <Duy at writeme.com> writes: 
>
>Hi,
>
>I'm presently involved with a university group experiment. We are
>investigating the effects of 2 point descrimination within the visual
>and auditory pathway and perhaps finding a link to Cortical dominance
>within the brain (i.e. the dominant hemisphere [left for right handers
>for example] will be better at the descrimination task than the lesser
>dominant).
>
>To test each eye indvidually, we used a flicker-fusion light source
>(flickering light bulb), varying the frequency of flicker to find the
>point where the source appears fused (non-blinking). The results show
no
>
>difference between the eyes.
>
>To test each ear individually, we used a white noise sound source,
>hooking it to a computer to allow the incorporation of 2 no-sound
>"blips". Separating these two breaks in the noise at varying times
>apart, in order to find the point where they appear fused (ie. as one
>"blip" instead of the two "Blip blip").
>
>We found that in all cases the right ear achieved a much higher degree
>of two-point descrimination, but have yet to come up with a reasonable
>conclusion as to why.
>
>We are presently looking into vestibular functions/anatomy but any
help
>would be greatly appreciated. Thanks
>
>Duy (2nd year student)
>
>
>




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