Transcript PPT only
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 • (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 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 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 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 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 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