The relationship between precursor level and the temporal effect

Abstract

Previous studies have suggested that temporal effects in masking may be consistent with a decrease in cochlear gain. One paradigm used to show this is to measure the level of a long-duration masker required to just mask a short-duration tone that occurs near masker onset. The temporal effect is revealed when the signal is detected at a lower signal-to-noise ratio following preceding stimulation (either an extension of the masker or a separate precursor). The present study examined whether this effect depends on precursor level. The signal was a 10-ms, 4-kHz tone. The masker was 200 ms. A fixed-level precursor had the same frequency characteristics as the masker, and was 205 ms. The masker and precursor had either no notch or a wide notch about the signal frequency. For a given precursor level, the growth of masker level with signal level was determined. These data were used to estimate input-output functions. The results are consistent with a graded decrease in gain at the signal frequency when there is no notch in the masker and precursor, and a graded decrease in suppression when there is a large notch. These results could be consistent with the action of the medial olivocochlear reflex.

Evaluating Adaptation and Olivocochlear Efferent Feedback as Potential Explanations of Psychophysical Overshoot

“…6 and 10). This finding strengthens the MOCR hypothesis and is consistent with the modeling findings from Strickland and colleagues (Strickland 2001(Strickland , 2004Strickland and Krishnan 2005;Strickland 2008), which were based on reducing basilar membrane gain (as suggested by von Klitzing and Kohlrausch 1994).…”

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

“…Given the purely psychophysical approach, it is difficult to prove that temporal effects in masking (e.g., Schmidt and Zwicker, 1991;von Klitzing and Kohlrausch, 1994;Strickland, 2001;Krull and Strickland, 2008;Jennings et al, 2009;Roverud and Strickland, 2010) are primarily due to the MOC reflex. Despite this, using the MOC reflex as a framework has proven useful in accounting for effects of the precursor across a variety of stimulus manipulations including: precursor level (Strickland, 2008), precursor duration and delay from masker onset (Roverud and Strickland, 2010;Jennings et al, 2011), and masker frequency (Jennings et al, 2009). Based on the results of the current experiment, this list can be expanded to include technique for measuring frequency selectivity (NNTC vs PTC) and signal level.…”

Auditory Enhancement of Increments in Spectral Amplitude Stems from More Than One Source

“…There is evidence that the MOCR is involved in a phenomenon akin to enhancement, "overshoot": the improvement in detectability of a brief tone as the tone is delayed from the onset of a broadband masker (Strickland 2004(Strickland , 2008Jennings et al 2011). The MOCR is mediated by the efferent system and operates directly at the level of the cochlea by modifying the action of the outer hair cells.…”

“…Enhancement has often been interpreted in terms of some form of selective neural adaptation: the precursor may adapt neural units responding to the nontarget components of the test sound more than neural units responding to the target component (Viemeister 1980); the benefit of the precursor may also originate from a reduction in the inhibition of the target component by the non-target components (Viemeister and Bacon 1982;Nelson and Young 2010;Byrne et al 2011). An alternative hypothesis is that the internal level of the non-target components, and as a consequence their ability to inhibit the target component, are reduced by the activation of the medial olivocochlear reflex (MOCR), which acts directly at the cochlear level (Strickland 2004(Strickland , 2008. Non-sensory mechanisms may also contribute to enhancement: the precursor could provide cues that help segregate the target component from the non-target components .…”