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Inner Ear Dysfunction

Inner Ear Dysfunction. Upcoming Talk: Isabelle Peretz Musical & Non-musical Brains Nov. 22 @ 12 noon + Lunch Rm 2068B South Building. Neural Correlates of Stream Segregation. Summation of cortical response hypothesis

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Inner Ear Dysfunction

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  1. Inner Ear Dysfunction Upcoming Talk: Isabelle Peretz Musical & Non-musical Brains Nov. 22 @ 12 noon + Lunch Rm 2068B South Building

  2. Neural Correlates of Stream Segregation • Summation of cortical response hypothesis • (DRAW) Will a stimulated area summate with another stimulated area on the tonotopic map? • Tetanic + rapid stimulation increases probability of summation (Fishman et al., 2001) ALTERNATIVELY? • Lesions of temporal cortex (in and around primary auditory cortex) (Peretz and colleagues, 1999; 2001) • Poster temporal gyrus affects melodic grouping • Intervals, melodic contours • Anterior temporal gyrus affects meter • Rhythmic grouping, temporal combinations

  3. Tinnitus: It has a certain ring to it (see Mencher pp. 144-145) • What is Tinnitus? • Ringing, buzzing, roaring, clicking experienced in one or both ears • Objective tinnitus • Audible to a third party • Stethoscope examination • Less than 5% of all tinnitus sufferers • Subjective tinnitus • Audible only to the patient • Subjective report • Approx. 35% of the population (continuous 15%) • Severe in 15% of tinnitus sufferers • Incidence increases with age & hearing loss • Noise-induced trauma

  4. Causes of Tinnitus • Vibratory • Acoustic stimulation of cochlea • Pulsatile tinnitus: Rhythmic pulsing, heartbeat • Leudet’s tinnitus: crackling of involuntary muscles • Jaw & neck position • Clicking tinnitus: Clicking sound that may occur with serous otitis media • May be objective or subjective • Non-vibratory • Neurochemical changes • Not traced to acoustic stimulation • Subjective tinnitus

  5. Physiological-subjective tinnitus (Jastreboff, 1990) • Cochlear causes • Increased otoacoustic emissions • Continuous spontaneous firing (4%) • Collapsing tectorial membrane • Chronic bent inner hair cells • Tetanic stimulation of auditory system • Reduced outer hair cell population • Inability to modulate gain • Chronic higher sensitivity to background noise • Hyperacusis: chronic oversensitivity (40% correlation) • Correlation with Sensori-neural hearing loss

  6. Higher-level Tinnitus(Lockwood et al., 1998) • Persistent symptoms after transection of auditory pathway • Cortical phenomenon? • fMRI evidence (blood flow) • Typical auditory stimulation = bilateral activation • Tinnitus causes unilateral activation • Modulation of tinnitus has unilateral effects • Neurochemical change in midbrain or cortex may contribute to tinnitus

  7. Summary & Treatments • Variety of contributing pathologies • Physical • Pinched blood vessel, loud-noise exposure, muscular activity, stress • Toxicity • Foods (allergic reactions), quinine, aspirin, cigarettes, alcohol, caffeine • Multiple causes • Treatments • Jaw position • Cutting cochlear nerve (50% effective) • Masking noise • Effectiveness of noise suggests no dementia • Hearing Aid use • Tinnitus retraining therapy • Habituation to tinnitus sound to reduce aversiveness

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