Efferent cochlear gain reduction is greatest when the precursor matches the signal frequency

Evidence

Masker levels at threshold obtained using a 4-kHz masker range from about 25 to 45 dB SPL, with the greatest masker level at threshold (about 45 dB SPL) associated with the presence of a precursor with a frequency close to that of the signal. Comparing masker levels at threshold for onand off-frequency maskers in the presence of a precursor (elicits efferent activation) with masker levels obtained in the absence of precursor (absence of efferent activation), it can be seen that the greatest change in masker level at threshold (of about 20 dB) occurs when there is an on-frequency masker, rather than an off-frequency masker, and this change is greatest when the precursor frequency is the same as, or just below, the 4-kHz signal. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5972

The frequency range of the efferent effect on cochlear gain was studied by presenting a bandlimited precursor sound centred at different frequencies prior to the onset of the combined FDMC masker-signal stimulus (see Fig. 1 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 5961

The FDMC method was used to obtain an estimate of the efferent effect in the absence (without a precursor) and presence (with a precursor presented at different frequencies) of efferent activation to investigate the frequency specificity of the efferent effect on cochlear gain. There was minimum cochlear gain reduction via efferent-activation when the precursor frequency was well removed from that of the signal frequency of 4-kHz, and maximal cochlear gain reduction (about 20 dB) when the precursor frequency was the same as, or close to, that of the signal. The results suggest that the efferent effect extends for precursors up to about 0.5–0.7 octaves above and below the signal frequency. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5980

Categorization

• SHARE: A colleague who studies efferent systems or cochlear mechanics would find this frequency-selective gain-reduction result specifically relevant.
• DEFINE: Clarifies how a precursor sound (prior stimulus) is used to manipulate cochlear gain via the efferent system before a test stimulus arrives.
• corroborated: 6 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 5972; Dijk, Pim van, Physiology, Psychoacoustics and…, 5961; Dijk, Pim van, Physiology, Psychoacoustics and…, 5980
• XREF: connects to: Brain efferents can dynamically adjust cochlear gain during listening; The modeled efferent effects likely generalize to natural acoustic hearing; The efferent-effect filter at 4 kHz has a Q10 of about 3.1 (+1 more)