Comparison of cochlear delay estimates using otoacoustic emissions and auditory brainstem responses

Area of Science:

• Auditory Neuroscience
• Human Physiology
• Bioacoustics

Background:

• Direct measurement of frequency-specific basilar membrane (BM) delays is challenging, often requiring invasive animal studies.
• Previous methods include laser velocimetry and auditory nerve fiber recordings, limiting human applicability.
• Non-invasive estimation of BM delays in humans is crucial for understanding cochlear mechanics.

Purpose of the Study:

• To non-invasively estimate frequency-specific basilar membrane (BM) delays in normal-hearing humans.
• To compare otoacoustic emission (OAE) delays with estimated BM delays across a wide frequency range.
• To provide evidence supporting the tonotopic origin and reverse traveling wave propagation of OAEs.

Main Methods:

• Utilized otoacoustic emissions (OAEs) and auditory brainstem responses (ABRs) for non-invasive delay estimation.
• Employed tone bursts across nine frequencies (0.5–8 kHz) as auditory stimuli.
• Calculated BM delays by subtracting neural and synaptic delays from ABR latency estimates.

Main Results:

• Successfully estimated BM delays non-invasively in normal-hearing human subjects.
• Demonstrated a close agreement between OAE delays and estimated BM delays across tested frequencies.
• Observed delays consistent with a tonotopic place of origin for OAEs.

Conclusions:

• Otoacoustic emissions (OAEs) likely originate from specific tonotopic places within the cochlea.
• The findings support the model of OAEs being generated by a reverse traveling wave.
• This non-invasive method provides valuable insights into cochlear mechanics and auditory function in humans.