1. Hearing & Aging Or age brings wisdom and other bad news

2. 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

3. 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

4. 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

5. 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

6. Temporal Synchrony Phase coding of auditory stimuli Normal: lock to wave peaks Older: Phase locking inconsistencies MacDonald et al., (under review) 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

7. 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

8. 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