Medial olivocochlear efferent feedback reduces cochlear gain most for frequencies near the signal

Evidence

Cochlear gain reduction via efferent feedback from the medial olivocochlear bundle is frequency specific … Efferent-mediated cochlear gain reduction was greatest for precursors with frequencies the same as, or close to that of, the signal (gain was reduced by about 20 dB), and least for precursors with frequencies well removed from that of the signal (gain remained at around 40 dB). The tuning of the efferent effect filter (tuning extending 0.5–0.7 octaves above and below the signal frequency) is within the range obtained in humans using otoacoustic emissions … The 10 dB bandwidth of the efferent-effect filter at 4000 Hz was about 1300 Hz (Q10 of 3.1). — Dijk, Pim van, Physiology, Psychoacoustics and…, 5950

Cochlear gain reduction via efferent feedback from the medial olivocochlear bundle is frequency specific (Guinan, Curr Opin Otolaryngol Head Neck Surg 18:447–453, 2010). The present study with humans used the Fixed Duration Masking Curve psychoacoustical method (Yasin et al., J Acoust Soc Am 133:4145–4155, 2013a; Yasin et al., Basic aspects of hearing: physiology and perception, pp 39–46, 2013b; Yasin et al., J Neurosci 34:15319–15326, 2014) to estimate the frequency specificity of the efferent effect at the cochlear level. The combined duration of the masker-plus-signal stimulus was 25 ms, within the efferent onset delay of about 31–43 ms (James et al., Clin Otolaryngol 27:106–112, 2002). Masker level (4.0 or 1.8 kHz) at threshold was obtained for a 4-kHz signal in the absence or presence of an ipsilateral 60 dB SPL, 160-ms precursor (200-Hz bandwidth) centred at frequencies between 2.5 and 5.5 kHz. Efferent-mediated cochlear gain reduction was greatest for precursors with frequencies the same as, or close to that of, the signal (gain was reduced by about 20 dB), and least for precursors with frequencies well removed from that of the signal (gain remained at around 40 dB). The tuning of the efferent effect filter (tuning extending 0.5–0.7 octaves above and below the signal frequency) is within the range obtained in humans using otoacoustic emissions (Lilaonitkul and Guinan, J Assoc Res Otolaryngol 10:459–470, 2009; Zhao and Dhar, J Neurophysiol 108:25–30, 2012). The 10 dB bandwidth of the efferent-effect filter at 4000 Hz was about 1300 Hz (Q10 of 3.1). The FDMC method can be used to provide an unbiased measure of the bandwidth of the efferent effect filter using ipsilateral efferent stimulation. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5951

The mammalian auditory system includes a brainstem-mediated efferent pathway from the superior olivary complex by way of the medial olivocochlear bundle (MOCB) which reduces the cochlear gain applied over time to the basilar membrane (BM) response to sound … The human MOCB response (as measured using otoacoustic emissions: OAEs) has an onset delay of between 25 and 40 ms and rise and decay time constants in the region of 280 and 160 ms, respectively (Backus and Guinan 2006 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 5954

Categorization

• DEFINE: Defines the efferent effect filter concept and its key quantitative parameter (10 dB bandwidth of 1300 Hz, Q10 of 3.1 at 4 kHz).
• XREF: Connects to the efferent onset delay and cochlear gain reduction mechanisms, themes central to psychoacoustics and physiology.
• corroborated: 3 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 5950; Dijk, Pim van, Physiology, Psychoacoustics and…, 5951; Dijk, Pim van, Physiology, Psychoacoustics and…, 5954