Detuning of Cochlear Action Potential Tuning Curves at High Sound Pressure Levels: Influence of Temporal, Spectral and Intensity Variables

Abstract

Action potential (AP) tuning curves (TCs), generated by probe stimuli of 60–65 dB SPL with short rise and decay (r&d) times, are less sensitive (have elevated tip thresholds) and are detuned (the frequency is shifted away from that of the probe stimulus, towards a middle frequency of the audiogram). These effects are more pronounced with forward than with simultaneous masking. TCs generated by masking tonal and narrow band noise stimuli are nearly identical, even though the spectrum is much wider for the noise stimulus. Decreasing r&d time has the same effect on TCs generated from both noise and tonal stimuli, even when it only measurably increases the acoustic splatter of the latter. Detuning appears to be related to a temporal-intensity interaction.

Key Words:

• Cochlear action potential
• Tuning curves
• Masking
• Gerbil
• Mouse