Quantifying 2-factor phase relations in non-linear responses from low characteristic-frequency auditory-nerve fibers

Area of Science:

• Auditory Neuroscience
• Computational Auditory Neuroscience
• Bioacoustics

Background:

• Auditory-nerve excitation may involve two response factors, potentially in antiphase, as suggested by non-linear interference.
• The conditions for antiphasic responses and their applicability to diverse auditory stimuli remain unclear.

Purpose of the Study:

• To systematically investigate the phase relationship of two hypothesized response factors in auditory-nerve fibers.
• To clarify the conditions under which these factors exhibit antiphasic or other phase relationships for various acoustic stimuli.

Main Methods:

• Utilized the MBPNL non-linear input/output model of cochlear frequency analysis.
• Simulated published data on level-dependent, non-linear responses from low characteristic-frequency (CF) auditory-nerve fibers.
• Analyzed responses to single clicks, paired clicks, single tones, and octave-band complex tones.

Main Results:

• Response factors are sensitive to phase differences, with paired-click transient responses requiring a quadrature phase.
• Complex-tone steady-state responses necessitate an antiphase relation between the two factors.
• MBPNL model simulations align with quadrature phase for transient and antiphase for steady-state responses in low-CF fibers.

Conclusions:

• The two-factor hypothesis, modeled by MBPNL, explains observed non-linear phenomena in auditory-nerve responses.
• A temporal transition from quadrature to antiphase response relations is hypothesized, possibly due to an adaptive cochlear mechanism.
• Further experimental and modeling research is proposed to explore this transition and refine auditory nerve models.