The "inverse problem" solved for a three-dimensional model of the cochlea. II. Application to experimental data sets

Area of Science:

• Auditory Neuroscience
• Bioacoustics
• Biophysics

Background:

• Classical cochlear models fail to replicate the high frequency selectivity observed in modern basilar membrane (BM) mechanical measurements.
• Locally active cochlear models offer a potential solution, but their necessity in the actual cochlea remains debated.

Purpose of the Study:

• To investigate whether recent mechanical experimental data of the basilar membrane (BM) motion can be simulated by a classical cochlear model.
• To determine if the cochlea requires local activity to explain observed BM response functions.

Main Methods:

• Applied an "inverse" problem-solving procedure to recent mechanical experimental data of BM motion.
• Recovered the BM impedance required to simulate specific BM response functions using a classical three-dimensional model.
• Resynthesized the model response using the recovered BM impedance to validate the method.

Main Results:

• The classical model requires local activity to accurately simulate recent BM measurement results, particularly in the peak response region.
• The inverse method proved accurate in the peak region, confirming the necessity of local activity.
• The recovered BM impedance, when used in resynthesis, validated the findings.

Conclusions:

• Recent experimental data unequivocally support the necessity of local activity within the cochlea.
• Classical cochlear models must incorporate local activity to achieve the frequency selectivity observed in vivo.
• The applied inverse method is a valid tool for analyzing cochlear mechanics and determining model requirements.