Signal durations under the efferent onset delay isolate the efferent effect on cochlear gain

Evidence

The FDMC method avoids the confounds of previous forward-masking methods used to measure the efferent effect by using a combined duration of the masker-plus-signal stimulus of 25 ms, which is within the efferent onset delay. Hence, the representation of the signal should be unaffected by efferent activity elicited by the masker. The effect of efferent activation on cochlear gain can then be separately studied by presenting a precursor sound (to activate the efferent system) prior to the onset of the combined FDMC masker-signal stimulus. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5953

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…, 5979

Categorization

Category: Causal Relationships

• DEFINE: Explains the timing logic of the FDMC method — a clean mechanism story worth preserving.
• XREF: The 25-40ms onset delay from the earlier paragraph is the key that makes this method work — a within-chapter causal chain.

Related

• Masking measured within the efferent onset delay isolates gain reduction cleanly (similarity 0.94)
• A 25 ms masker-plus-signal window isolates the signal from efferent feedback. (similarity 0.90)
• Efferent cochlear gain reduction is greatest when the precursor matches the signal frequency (similarity 0.89)
• Efferent gain effects were mapped by precursors swept across nine centre frequencies (similarity 0.89)
• Psychoacoustic forward masking can probe the efferent reflex without its own contamination. (similarity 0.89)
• The efferent olivocochlear reflex takes 25-40 ms to begin acting (similarity 0.88)
• Otoacoustic and psychophysical estimates of efferent gain disagree due to stimulus constraints (similarity 0.86)
• The modeled efferent effects likely generalize to natural acoustic hearing (similarity 0.85)
• Medial olivocochlear efferent feedback reduces cochlear gain most for frequencies near the signal (similarity 0.85)
• Efferent cochlear gain reduction is frequency-selective around the signal frequency. (similarity 0.84)
• Brain efferents can dynamically adjust cochlear gain during listening (similarity 0.84)
• The human efferent reflex to sound has an onset delay of 25-40 ms (similarity 0.83)
• The efferent effect is frequency-tuned along the cochlear tonotopic axis in humans (similarity 0.83)
• Medial olivocochlear efferents actively modulate cochlear gain during binaural listening (similarity 0.82)
• Masker duration gates whether the medial olivocochlear reflex contributes to measured gain (similarity 0.82)

Broader Connections

• Otoacoustic and psychophysical estimates of efferent gain disagree due to stimulus constraints #qualifies (0.75) — Dijk, Pim van, Physiology, Psychoacoustics and…, 5981