Transcript PPT only
Hearing & Aging
Or age brings wisdom and other bad
news
Presbyacusis
Age-related hearing loss
Degeneration of the inner ear
Largest decline over 2kHz
Low frequency hearing relatively
unaffected
Incidence
100% of population will develop
minimal hearing loss
30% over 65 & 40% over 75
moderate to severe hearing loss
Gender Affects Hearing
Presbyacusis & Gender (Jerger et al., 1993)
Female hearing
Degrades 2 dB HL per decade
Larger deficits below 1 kHz than men
Cause?
Male hearing
Degrades 3 dB HL per decade
Largest deficits above 1 kHz
Noise induced threshold shift
Cause of Presbyacusis
Central/cortical
Evidence
Deficits in multiple sensory systems
Correlated cross-sensory degradation
Histological support counter claim
Cochlear
Evidence
ABR highly latent to acoustic stimulation
Change in Outer Hair Cell functioning
Otoacoustic emissions decrease with age, higher
threshold
(Outer hair cell generated sound)
Change in inner hair cell density
Reduced hair in the initial 1/3 of basilar membrane
Why should more high freq. hair cells be damaged?
Change in basilar membrane stiffness
More bad news: Recruitment
Loudness recruitment
DEMO
Outer hair cell dysfunction
All or nothing
Normal outer hair cell response
Non-linear gain control
Loudness recruitment
Latent response to stimulation
Increased threshold
Sudden engagement
Temporal Synchrony
Phase coding of auditory stimuli
MacDonald et al., (under review)
Normal: lock to wave peaks
Older: Phase locking inconsistencies
Compare sentence comprehension of
younger adult ‘jittered’ speech with
normal older adults
DEMO JITTERED SPEECH
Equal performance across age groups
Replicates findings in speech paradigms
Effects of Age-related Hearing Losses
Signal processing load
Normal hearing: auditory restoration and
processing
Older hearing: increased demand for auditory
restoration and processing
‘Cascade Up’
Greater effort for hearing
Decreased resources/efficiency
Effects speeded processing, multiple operations
Berlin Aging Study (Baltes & Lindenberger, 1997)
Majority of cognitive aging = sensory degradation
Studies of Speeded Speech
Older vs. Younger adult (Schneider et al., under
review)
Three methods of speeding speech
Increasing tape speed
Removing every third 10 ms segment
Reducing steady-state formants by 90%
How will younger and older adults respond?
Method of speeding speech causes
age-related differences
Actual speed does not affect older adults