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Is off-frequency overshoot caused by adaptation of suppression?

Fletcher M, de Boer J, Krumbholz K - J. Assoc. Res. Otolaryngol. (2014)

Bottom Line: This study is concerned with the mechanism of off-frequency overshoot.Overshoot refers to the phenomenon whereby a brief signal presented at the onset of a masker is easier to detect when the masker is preceded by a "precursor" sound (which is often the same as the masker).Overshoot is most prominent when the masker and precursor have a different frequency than the signal (henceforth referred to as "off-frequency overshoot").

View Article: PubMed Central - PubMed

Affiliation: , Nottingham, UK.

ABSTRACT
This study is concerned with the mechanism of off-frequency overshoot. Overshoot refers to the phenomenon whereby a brief signal presented at the onset of a masker is easier to detect when the masker is preceded by a "precursor" sound (which is often the same as the masker). Overshoot is most prominent when the masker and precursor have a different frequency than the signal (henceforth referred to as "off-frequency overshoot"). It has been suggested that off-frequency overshoot is based on a similar mechanism as "enhancement," which refers to the perceptual pop-out of a signal after presentation of a precursor that contains a spectral notch at the signal frequency; both have been proposed to be caused by a reduction in the suppressive masking of the signal as a result of the adaptive effect of the precursor ("adaptation of suppression"). In this study, we measured overshoot, suppression, and adaptation of suppression for a 4-kHz sinusoidal signal and a 4.75-kHz sinusoidal masker and precursor, using the same set of participants. We show that, while the precursor yielded strong overshoot and the masker produced strong suppression, the precursor did not appear to cause any reduction (adaptation) of suppression. Predictions based on an established model of the cochlear input-output function indicate that our failure to obtain any adaptation of suppression is unlikely to represent a false negative outcome. Our results indicate that off-frequency overshoot and enhancement are likely caused by different mechanisms. We argue that overshoot may be due to higher-order perceptual factors such as transient masking or attentional diversion, whereas enhancement may be based on mechanisms similar to those that generate the Zwicker tone.

No MeSH data available.


Related in: MedlinePlus

Simulated cochlear input–output (IO) functions of the signal in the suppression experiment. The bold black line, labelled f, shows the IO function when the signal is presented alone and is thus unsuppressed. The bold red line, labelled fsS, shows the IO function when the signal is presented together with the masker and is thus suppressed. The grey vertical line shows the average sound pressure level of the signal. The horizontal black and red arrows show the response levels of the unsuppressed (ES) and suppressed signal (EsS), respectively. The dashed blue line, labelled fasS, shows the simulated signal IO function in the presence of both the masker and precursor (to be discussed in the adaptation-of-suppression experiment). In this example, it was assumed that all of the measured overshoot was caused by adaptation of suppression. The model results shown here are based on the averaged data across participants and are for illustration only. The model predictions presented in the text are based on the individual data.
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Fig4: Simulated cochlear input–output (IO) functions of the signal in the suppression experiment. The bold black line, labelled f, shows the IO function when the signal is presented alone and is thus unsuppressed. The bold red line, labelled fsS, shows the IO function when the signal is presented together with the masker and is thus suppressed. The grey vertical line shows the average sound pressure level of the signal. The horizontal black and red arrows show the response levels of the unsuppressed (ES) and suppressed signal (EsS), respectively. The dashed blue line, labelled fasS, shows the simulated signal IO function in the presence of both the masker and precursor (to be discussed in the adaptation-of-suppression experiment). In this example, it was assumed that all of the measured overshoot was caused by adaptation of suppression. The model results shown here are based on the averaged data across participants and are for illustration only. The model predictions presented in the text are based on the individual data.

Mentions: In the current implementation of this model, which is similar to the one used by (Yasin and Plack 2003), the cochlear IO function, f, was expressed as the sum of the sound level, L, and a level-dependent gain, G(L); in units of intensity: f(L) = 10(L + G(L))/10 (Fig. 4, black line). At low sound levels up to a first break point, BP1, the gain was assumed to be constant at the maxim value Gmax:1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ G\left(L\le B{P}_1\right)={G}_{\max } $$\end{document}GL≤BP1=GmaxFIG. 4


Is off-frequency overshoot caused by adaptation of suppression?

Fletcher M, de Boer J, Krumbholz K - J. Assoc. Res. Otolaryngol. (2014)

Simulated cochlear input–output (IO) functions of the signal in the suppression experiment. The bold black line, labelled f, shows the IO function when the signal is presented alone and is thus unsuppressed. The bold red line, labelled fsS, shows the IO function when the signal is presented together with the masker and is thus suppressed. The grey vertical line shows the average sound pressure level of the signal. The horizontal black and red arrows show the response levels of the unsuppressed (ES) and suppressed signal (EsS), respectively. The dashed blue line, labelled fasS, shows the simulated signal IO function in the presence of both the masker and precursor (to be discussed in the adaptation-of-suppression experiment). In this example, it was assumed that all of the measured overshoot was caused by adaptation of suppression. The model results shown here are based on the averaged data across participants and are for illustration only. The model predictions presented in the text are based on the individual data.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4368652&req=5

Fig4: Simulated cochlear input–output (IO) functions of the signal in the suppression experiment. The bold black line, labelled f, shows the IO function when the signal is presented alone and is thus unsuppressed. The bold red line, labelled fsS, shows the IO function when the signal is presented together with the masker and is thus suppressed. The grey vertical line shows the average sound pressure level of the signal. The horizontal black and red arrows show the response levels of the unsuppressed (ES) and suppressed signal (EsS), respectively. The dashed blue line, labelled fasS, shows the simulated signal IO function in the presence of both the masker and precursor (to be discussed in the adaptation-of-suppression experiment). In this example, it was assumed that all of the measured overshoot was caused by adaptation of suppression. The model results shown here are based on the averaged data across participants and are for illustration only. The model predictions presented in the text are based on the individual data.
Mentions: In the current implementation of this model, which is similar to the one used by (Yasin and Plack 2003), the cochlear IO function, f, was expressed as the sum of the sound level, L, and a level-dependent gain, G(L); in units of intensity: f(L) = 10(L + G(L))/10 (Fig. 4, black line). At low sound levels up to a first break point, BP1, the gain was assumed to be constant at the maxim value Gmax:1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ G\left(L\le B{P}_1\right)={G}_{\max } $$\end{document}GL≤BP1=GmaxFIG. 4

Bottom Line: This study is concerned with the mechanism of off-frequency overshoot.Overshoot refers to the phenomenon whereby a brief signal presented at the onset of a masker is easier to detect when the masker is preceded by a "precursor" sound (which is often the same as the masker).Overshoot is most prominent when the masker and precursor have a different frequency than the signal (henceforth referred to as "off-frequency overshoot").

View Article: PubMed Central - PubMed

Affiliation: , Nottingham, UK.

ABSTRACT
This study is concerned with the mechanism of off-frequency overshoot. Overshoot refers to the phenomenon whereby a brief signal presented at the onset of a masker is easier to detect when the masker is preceded by a "precursor" sound (which is often the same as the masker). Overshoot is most prominent when the masker and precursor have a different frequency than the signal (henceforth referred to as "off-frequency overshoot"). It has been suggested that off-frequency overshoot is based on a similar mechanism as "enhancement," which refers to the perceptual pop-out of a signal after presentation of a precursor that contains a spectral notch at the signal frequency; both have been proposed to be caused by a reduction in the suppressive masking of the signal as a result of the adaptive effect of the precursor ("adaptation of suppression"). In this study, we measured overshoot, suppression, and adaptation of suppression for a 4-kHz sinusoidal signal and a 4.75-kHz sinusoidal masker and precursor, using the same set of participants. We show that, while the precursor yielded strong overshoot and the masker produced strong suppression, the precursor did not appear to cause any reduction (adaptation) of suppression. Predictions based on an established model of the cochlear input-output function indicate that our failure to obtain any adaptation of suppression is unlikely to represent a false negative outcome. Our results indicate that off-frequency overshoot and enhancement are likely caused by different mechanisms. We argue that overshoot may be due to higher-order perceptual factors such as transient masking or attentional diversion, whereas enhancement may be based on mechanisms similar to those that generate the Zwicker tone.

No MeSH data available.


Related in: MedlinePlus