OAEs Through the Life Span

Transcription

1 OAEs Through the Life Span Sumitrajit Dhar, PhD Fellow, Hugh Knowles Center for Hearing Science Professor, Roxelyn & Richard Pepper Department of Communication Sciences and Disorders Northwestern University Evanston, IL Otoacoustic Emissions Distortion Product Otoacoustic Emissions DPOAEs in Early Life Measurement Complications in Human Subjects Midlife crisis of DPOAEs DPOAEs in Older Adults Now what? Otoacoustic Emissions Spontaneous Transient Evoked Stimulus Frequency Otoacoustic Emissions Distortion Product 1

2 Lessons from Kemp, 1978 Random noise recorded when closed cavity is stimulated with a click. Same stimulus in human ear shows response lasting beyond 10 ms TEOAE. Different delays for responses to tone bursts of different frequencies cochlear origin. Site of Generation Cochlea: observed delay in OAEs; recordings from BM & auditory nerve. Outer Hair Cells: concomitant ablation of OAEs and OHC (e.g., Davis et. al., 2002); loss of OAEs due to other insults associated with OHC damage (salicylate, noise, etc.). But where in the OHC? 2

3 Prestin KO Liberman et al., 2004 Verpy et. al., (2008); Nature Liberman et al.,

4 Cochlea Outer Hair Cell Stereocilia (transducer) Soma (?amplifier) Olivocochlear efferents Middle ear transmission Classification STIMULUS Without stimulation Spontaneous Stimulated Transient Distortion product Stimulus frequency Mechanism-Based Classification Phase (cycles) DPOAE SFOAE Frequency (Hz) 4

5 DPOAE Phase stapes base apex Approximate scaling symmetry of the cochlea (at least in the basal half) results in invariant DPOAE phase as a function of frequency. SFOAE Phase stapes base apex Steep SFOAE phase gradient suggests a place fixed mechanism of SFOAE re-emission. Zweig, Shera (1995 on) stapes base input apex Incoming signal is reflected randomly by outer hair cells; some reflections are coherent and contribute to the outwardtraveling energy. Coherent reflectors near the peak region of the traveling wave have enough magnitude to contribute significantly to earcanal OAE. 5

6 Classification STIMULUS Without stimulation Spontaneous Stimulated Transient Distortion product Stimulus frequency MECHANISM Reflection Spontaneous Mixed DPOAE TEOAE SFOAE Distortion DPOAE DPOAE Generation f1 f2 outer ear middle ear f2 f1 6

7 outer ear middle ear f2 f1 composite reflection nonlinear Talmadge, Long, Tubis & Dhar (1999); JASA model Talmadge, Long, Tubis & Dhar (1999); JASA DPOAE Fine Structure 7

8 Inverse FFT + Time Windowing = Separate DPOAE components Otoacoustic Emissions Distortion Product Otoacoustic Emissions The early life of the inner ear Measurement Complications in Human Subjects Midlife crisis of the inner ear The older inner ear Now what? 8

9 DPOAE Components 9

10 DPOAEs change rapidly in very early life. These changes are most likely associated with changes in outer and middle ears. Peak DPOAE levels appear to be achieved at 6-8 months of age. Reflection DPOAEs appear to decline more rapidly after 6-8 months of age. Otoacoustic Emissions Distortion Product Otoacoustic Emissions The early life of the inner ear Measurement Complications in Human Subjects Midlife crisis of the inner ear The older inner ear Now what? with Jonathan Siegel Steve Zecker David Klodd Vickie Hellyer Rebecca Abel Jungmee Lee Gayla Poling Funding: National Institutes of Health 10

11 Calibration need calibrated signals at the eardrum. We currently use signals calibrated at the emission microphone. Need a sound delivery system capable of meaningful levels at the eardrum at 20kHz. Need a linear system so biological distortion can be recorded at higher input levels. From Lee et al. (2012) Ear & Hearing From Lee et al. (2012) Ear & Hearing 11

12 Edge yo yo change between yrs yo Hearing loss evident in yo group. Dramatic decline and expansion between years. All subjects would currently qualify as normal. Hearing Thresholds Otoacoustic Emissions Distortion Product Otoacoustic Emissions The early life of the inner ear Measurement Complications in Human Subjects Midlife crisis of the inner ear The older inner ear Now what? 12

13 From Poling et al. (2014) JARO Edge yo change yrs yo yo Clinically significant DPOAE loss evident in yo group; Five year lead on hearing thresholds. Dramatic decline and expansion between years. All frequencies affected by age 40. DPOAEs 55/40 From Poling et al. (2014) JARO 13

14 75/75 Otoacoustic Emissions Distortion Product Otoacoustic Emissions The early life of the inner ear Measurement Complications in Human Subjects Midlife crisis of the inner ear The older inner ear Now what? 14

15 DPOAE Components 15

16 DPOAEs can be reliably recorded through the entire cochlea, given a carefully built system and properly implemented calibration. DPOAEs change rapidly in early life reflecting the maturing outer and middle ears. DPOAE changes at the base of the cochlea are observable just after the teenage years, likely reflecting early age-related changes in cochlear amplification. Both level and phase changes in DPOAEs are observed in the older ear. Different DPOAE components change at different rates during different life epochs. Now what? Make systems and techniques available to the clinician. Change measurement parameters to reflect cochlear mechanics in different parts of the cochlea. Accumulate normative data for whole cochlea for different age groups. Longitudinal studies to understand and then predict aging trajectory in individuals. Q&A To ask a question, please type your question into the chat box in the lower left corner of the screen and click on the Send button located right below the box. 16

17 Thank you 17