Re: Bite-induced pitch shift?

[Peter Cariani <peter@xxxxxxxxxxxxxxxxxxxx>]

I asked Bob Levine about these pitch shifts and the clench-induced
tinnitus he
is studying (which I can hear if I clench my jaw hard in an acoustic
isolation chamber).
He thinks they could very well be related to the reported pitch shifts.

So now we have explanations for this phenomenon that span the auditory
chain
from tympanic muscle to cochlea to cochlear nucleus. How and why these
various
effects would modulate an existing pitch rather than creating a second
perceived
pitch is beyond me. What is known about the interaction of tinnitus
percepts with
those evoked the normal (acoustic) route?

-- Peter Cariani

I relay the abstract of their upcoming paper:

Exp. Brain Res. (in press)

Tinnitus studies: Muscle spindles appear to initiate central nervous
system auditory - somatosensory interactions

Levine RA, Abel M and Cheng H

Massachusetts Eye and Ear Infirmary; Massachusetts General Hospital;
Harvard Medical School; Harvard Dental School; Massachusetts Institute
of Technology, Boston

Abstract
Evidence has been accumulating linking clinical tinnitus to the
somatosensory system.  Most clinical tinnitus patients can change the
acoustic properties of their tinnitus with forceful head and neck
contractions.  The significance of such somatic modulation of tinnitus
was assessed by testing non-clinical subjects.  Like clinical tinnitus
patients about 80% of non-clinical subjects who had ongoing tinnitus at
the time of testing (whether or not they had been previously aware of
it) could modulate their tinnitus with head and neck contractions.
Almost 60% of those with no tinnitus at the time of testing could
elicit a tinnitus-like auditory percept with head and neck
contractions.  Because similar results were found in the profoundly
deaf, we conclude that somatosensory-auditory interactions within the
central nervous system are accounting for most, if not all, somatic
modulation of tinnitus as well as the development of auditory percepts
with somatic testing.  Other observations implicate the muscle spindle
as initiating the neural activation that ultimately modulates the
central auditory pathway, including the dorsal cochlear nucleus.
Somatic influences upon auditory perception are not limited to tinnitus
subjects but are a fundamental property of the auditory system.