Inner Ear DysfunctionInner Ear Dysfunction

Upcoming Talk: Isabelle PeretzUpcoming Talk: Isabelle PeretzMusical & Non-musical BrainsMusical & Non-musical BrainsNov. 22 @ 12 noon + LunchNov. 22 @ 12 noon + LunchRm 2068B South BuildingRm 2068B South Building

Neural Correlates of Stream Neural Correlates of Stream SegregationSegregation

Summation of cortical response hypothesisSummation of cortical response hypothesis• (DRAW) Will a stimulated area summate with (DRAW) Will a stimulated area summate with

another stimulated area on the tonotopic map? another stimulated area on the tonotopic map? Tetanic + rapid stimulation increases probability of Tetanic + rapid stimulation increases probability of

summation (Fishman et al., 2001)summation (Fishman et al., 2001)

ALTERNATIVELY?ALTERNATIVELY? Lesions of temporal cortex (in and around Lesions of temporal cortex (in and around

primary auditory cortex) primary auditory cortex) (Peretz and colleagues, 1999; 2001)(Peretz and colleagues, 1999; 2001)

• Poster temporal gyrus affects melodic groupingPoster temporal gyrus affects melodic grouping Intervals, melodic contoursIntervals, melodic contours

• Anterior temporal gyrus affects meterAnterior temporal gyrus affects meter Rhythmic grouping, temporal combinationsRhythmic grouping, temporal combinations

Tinnitus: It has a certain ring to it Tinnitus: It has a certain ring to it (see Mencher pp. 144-145)(see Mencher pp. 144-145)

What is Tinnitus? What is Tinnitus? • Ringing, buzzing, roaring, clicking experienced in Ringing, buzzing, roaring, clicking experienced in

one or both earsone or both ears Objective tinnitusObjective tinnitus

• Audible to a third partyAudible to a third party Stethoscope examinationStethoscope examination Less than 5% of all tinnitus sufferersLess than 5% of all tinnitus sufferers

Subjective tinnitusSubjective tinnitus• Audible only to the patientAudible only to the patient

Subjective reportSubjective report Approx. 35% of the population (continuous 15%)Approx. 35% of the population (continuous 15%)

• Severe in 15% of tinnitus sufferersSevere in 15% of tinnitus sufferers Incidence increases with age & hearing lossIncidence increases with age & hearing loss

• Noise-induced traumaNoise-induced trauma

Causes of TinnitusCauses of Tinnitus VibratoryVibratory

• Acoustic stimulation of cochleaAcoustic stimulation of cochlea Pulsatile tinnitus: Rhythmic pulsing, Pulsatile tinnitus: Rhythmic pulsing,

heartbeatheartbeat Leudet’s tinnitus: crackling of involuntary Leudet’s tinnitus: crackling of involuntary

musclesmuscles• Jaw & neck positionJaw & neck position

Clicking tinnitus: Clicking sound that Clicking tinnitus: Clicking sound that may occur with serous otitis media may occur with serous otitis media

• May be objective or subjectiveMay be objective or subjective Non-vibratoryNon-vibratory

• Neurochemical changesNeurochemical changes Not traced to acoustic stimulationNot traced to acoustic stimulation

• Subjective tinnitusSubjective tinnitus

Physiological-subjective tinnitus Physiological-subjective tinnitus (Jastreboff, 1990)(Jastreboff, 1990)

Cochlear causesCochlear causes• Increased otoacoustic emissionsIncreased otoacoustic emissions

Continuous spontaneous firing (4%)Continuous spontaneous firing (4%)

• Collapsing tectorial membraneCollapsing tectorial membrane Chronic bent inner hair cellsChronic bent inner hair cells Tetanic stimulation of auditory systemTetanic stimulation of auditory system

• Reduced outer hair cell populationReduced outer hair cell population Inability to modulate gainInability to modulate gain Chronic higher sensitivity to background noiseChronic higher sensitivity to background noise

• Hyperacusis: chronic oversensitivity (40% correlation)Hyperacusis: chronic oversensitivity (40% correlation)

Correlation with Sensori-neural hearing Correlation with Sensori-neural hearing lossloss

Higher-level TinnitusHigher-level Tinnitus(Lockwood et al., 1998)(Lockwood et al., 1998)

Persistent symptoms after Persistent symptoms after transection of auditory pathwaytransection of auditory pathway• Cortical phenomenon? Cortical phenomenon?

fMRI evidence (blood flow)fMRI evidence (blood flow)• Typical auditory stimulation = bilateral Typical auditory stimulation = bilateral

activationactivation• Tinnitus causes unilateral activationTinnitus causes unilateral activation

Modulation of tinnitus has unilateral effectsModulation of tinnitus has unilateral effects

Neurochemical change in midbrain Neurochemical change in midbrain or cortex may contribute to tinnitusor cortex may contribute to tinnitus

Summary & TreatmentsSummary & Treatments Variety of contributing pathologiesVariety of contributing pathologies

• PhysicalPhysical Pinched blood vessel, loud-noise exposure, muscular Pinched blood vessel, loud-noise exposure, muscular

activity, stressactivity, stress• ToxicityToxicity

Foods (allergic reactions), quinine, aspirin, cigarettes, Foods (allergic reactions), quinine, aspirin, cigarettes, alcohol, caffeinealcohol, caffeine

• Multiple causesMultiple causes TreatmentsTreatments

• Jaw position Jaw position • Cutting cochlear nerve (50% effective)Cutting cochlear nerve (50% effective)• Masking noiseMasking noise

Effectiveness of noise suggests no dementiaEffectiveness of noise suggests no dementia• Hearing Aid useHearing Aid use• Tinnitus retraining therapyTinnitus retraining therapy

Habituation to tinnitus sound to reduce aversivenessHabituation to tinnitus sound to reduce aversiveness