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