Recovery from prior stimulation II: Effects upon intensity discrimination

Notched-noise precursors improve detection of low-frequency amplitude modulation

“…The relatively higher thresholds from Carlyon and Moore (1984) are likely due to differences between AM detection and intensity discrimination and due to their pedestal being roughly half the duration of the 50-ms carrier. The mid-level hump seen in intensity discrimination studies (e.g., Carlyon and Moore, 1984;Zeng et al, 1991) was originally hypothesized to be due to a threshold gap between low-and high-SR fibers. A quantitative evaluation of this hypothesis (Heinz et al, 2001) showed that (1) the transition in coding from high-, to low-SR fibers was at higher levels than those associated with the mid-level effects observed psychophysically, and (2) the presence of medium-SR fibers (Liberman, 1978) eliminated the putative threshold gap, casting doubt on this hypothesis.…”

“…However, for short ( 30 ms), narrow-band pedestals, intensity resolution deteriorates at moderate pedestal levels (Carlyon and Moore, 1984;Nizami, 2006;Roverud and Strickland, 2015a). This deterioration has been termed the "severedeparture from Weber's law" (Carlyon and Moore, 1984) or the "mid-level hump" (Zeng et al, 1991;Nizami, 2006) and is consistent with basilar membrane mechanics which exhibit compressive non-linearity at mid-to-high levels for tones presented at the characteristic frequency (CF) (Heinz et al, 2001;Pienkowski and Hagerman, 2009;Roverud and Strickland, 2015a). Moreover, recent studies have shown that the mid-level hump is reduced (i.e., performance improves at moderate pedestal levels) when a short pedestal is preceded by a long (e.g., 150 ms) ipsilateral or bilateral noise ("precursor"), consistent with a reduction in cochlear gain over the course of the precursor, perhaps via the medial olivocochlear (MOC) reflex (Roverud and Strickland, 2015b).…”

Binaural release from masking in forward-masked intensity discrimination: Evidence for effects of selective attention

“…An important finding is that with an intense masker (e.g., 90 dB SPL) the masker-induced elevation of the intensity difference limen (DL) is smaller for both a low-level and a high-level standard than for a mid-level standard. Thus, the relationship between standard level and the DL-elevation is non-monotonic, showing the so-called mid-level hump in intensity discrimination (Zeng et al, 1991). Several explanations for this somewhat counterintuitive result have been proposed (for reviews see Oberfeld, 2008Oberfeld, , 2009.…”

Effects of masker envelope coherence on intensity discrimination

“…Several groups have demonstrated that intensity discrimination can be disrupted by nonsimultaneous masking noise even if that noise does not affect detection threshold ͑e.g., Zeng et al, 1991;Carlyon and Beveridge, 1993;Plack et al, 1995;Plack, 1996;Oberfeld, 2008͒. Intensity discrimination in nonsimultaneous masking conditions appears to be quite complex and is not fully understood ͑see Zeng, 1998;Oberfeld, 2008͒, but one possible explanation is that maskers presented before or after the signal could interfere with the trace memory representing the intensity in each interval, particularly if the masker has prominent inherent fluctuation ͑Plack et al, 1995͒.…”