The time course of cochlear gain reduction measured using a more efficient psychophysical technique

Abstract

In a previous study it was shown that an on-frequency precursor intended to activate the medial olivocochlear reflex ͑MOCR͒ at the signal frequency reduces the gain estimated from growth-of-masking ͑GOM͒ functions. This is called the temporal effect ͑TE͒. In Expt. 1 a shorter method of measuring this change in gain is established. GOM functions were measured with an onand off-frequency precursor presented before the masker and signal, and used to estimate Input/ Output functions. The change in gain estimated in this way was very similar to that estimated from comparing two points measured with a single fixed masker level on the lower legs of the GOM functions. In Expt. 2, the TE was measured as a function of precursor duration and signal delay. For short precursor durations and short delays the TE increased ͑buildup͒ or remained constant as delay increased, then decreased. The TE also increased with precursor duration for the shortest delay. The results were fitted with a model based on the time course of the MOCR. The model fitted the data well, and predicted the buildup. This buildup is not consistent with exponential decay predicted by neural adaptation or persistence of excitation.

Computational Modeling of Individual Differences in Behavioral Estimates of Cochlear Nonlinearities

“…The ability to identify and group efficient and inefficient listeners may serve as a method for accounting for extraneous sources of variance when analyzing data from masking experiments. The variance in the input SMR not accounted for by k may originate in mechanisms not included in the model's architecture, such as the MOC reflex (Krull and Strickland 2008;Jennings et al 2009;Wojtczak and Oxenham 2009;Roverud and Strickland 2010;Wojtczak and Oxenham 2010;Aguilar et al 2013). However, the current lack of an independent measure of MOC reflex strength in humans prevents a quantitative assessment of the variance accounted for by this potential factor.…”

Evaluating the effects of olivocochlear feedback on psychophysical measures of frequency selectivity

“…Thus, the 10-15 dB threshold shift criterion ensures the amount of gain reduction was similar across subjects. Second, restricting precursor levels to be a multiple of 10 facilitates comparison with previous studies that also used this criterion (e.g., Krull and Strickland, 2008;Jennings et al, 2009;Jennings and Strickland, 2010;Roverud and Strickland, 2010). Quiet threshold and precursor levels for each subject are shown in Table I.…”

“…In these instances, this is largely due to the simplicity of its first stage (cochlear filtering and non-linearity). For example, the model lacks the cochlear processes associated with suppression and medial olivocochlear feedback and as such does not predict psychophysical suppression (Houtgast, 1972), overshoot (Zwicker, 1965), and temporal effects in forward masking (e.g., Jennings et al, 2009;Jennings and Strickland, 2010;Roverud and Strickland, 2010). Plack et al (2002) replaced the first stage of the temporal window model with a robust cochlear model developed by Meddis and colleagues Lopez-Poveda and Meddis, 2001).…”

Modeling the Time-Varying and Level-Dependent Effects of the Medial Olivocochlear Reflex in Auditory Nerve Responses

“…The time (1990) data, and was generated using the "shocks" setting of the model. delay in the output corresponds to estimates of the onset and offset delay in humans through otoacoustic emission and behavioral data (Backus and Guinan 2006;Roverud and Strickland 2010;Jennings et al 2011). The smoothing filter not only provides a delay in the actual system but also helps to make sure that the input to the LD function does not sharply alternate between sections of the piecewise function on a sample-by-sample basis.…”