Subject: Re: Bite-induced pitch shift? From: Peter Cariani <peter(at)EPL.MEEI.HARVARD.EDU> Date: Fri, 20 Jun 2003 16:17:09 -0400
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.