Limits...
Neuronal precision and the limits for acoustic signal recognition in a small neuronal network.

Neuhofer D, Stemmler M, Ronacher B - J. Comp. Physiol. A Neuroethol. Sens. Neural. Behav. Physiol. (2010)

Bottom Line: By progressively corrupting the envelope of a female song, we determined the critical degradation level at which males failed to recognize a courtship call in behavioral experiments.At consecutive levels of processing, intrinsic variability increased, while the sensitivity to external noise decreased.We followed two approaches to determine critical degradation levels from spike train dissimilarities, and compared the results with the limits of signal recognition measured in behaving animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Humboldt-Universität zu Berlin, Invalidenstrasse 43, 10115, Berlin, Germany. neuhofda@cms.hu-berlin.de

ABSTRACT
Recognition of acoustic signals may be impeded by two factors: extrinsic noise, which degrades sounds before they arrive at the receiver's ears, and intrinsic neuronal noise, which reveals itself in the trial-to-trial variability of the responses to identical sounds. Here we analyzed how these two noise sources affect the recognition of acoustic signals from potential mates in grasshoppers. By progressively corrupting the envelope of a female song, we determined the critical degradation level at which males failed to recognize a courtship call in behavioral experiments. Using the same stimuli, we recorded intracellularly from auditory neurons at three different processing levels, and quantified the corresponding changes in spike train patterns by a spike train metric, which assigns a distance between spike trains. Unexpectedly, for most neurons, intrinsic variability accounted for the main part of the metric distance between spike trains, even at the strongest degradation levels. At consecutive levels of processing, intrinsic variability increased, while the sensitivity to external noise decreased. We followed two approaches to determine critical degradation levels from spike train dissimilarities, and compared the results with the limits of signal recognition measured in behaving animals.

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Robustness of signal recognition measured in behavioral tests with degraded female songs. a Phonotaxis responses of seven male grasshoppers. Abscissa: degradation levels in dB; ‘n’ indicates pure noise. Ordinate: the percentage of phonotactic turning responses; 100% means that the male reacted to every stimulus presentation. Behavioral critical degradation levels (bCDL) were determined at the intersection of each curve with the 50% response level (see arrow). b bCDL of 59 animals
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Fig4: Robustness of signal recognition measured in behavioral tests with degraded female songs. a Phonotaxis responses of seven male grasshoppers. Abscissa: degradation levels in dB; ‘n’ indicates pure noise. Ordinate: the percentage of phonotactic turning responses; 100% means that the male reacted to every stimulus presentation. Behavioral critical degradation levels (bCDL) were determined at the intersection of each curve with the 50% response level (see arrow). b bCDL of 59 animals

Mentions: Males of C. biguttulus were used for the behavioral tests, in which the same stimuli were used as in electrophysiology. The playback experiments were performed at 30 ± 2°C in an anechoic chamber. Whenever a male started to sing, a model song was broadcast from a loudspeaker situated laterally. Each song was presented at least 10 times in pseudo-random order at an intensity of 60 dB SPL. The phonotactic behavior of the animal, whether it turned towards the loudspeaker or not, was monitored visually and journalized. The response probability to the different types of song models was calculated as the percentage of turning responses relative to the total number of stimulus presentations. We interpolated the degradation level that caused a decrease of turning response to 50% (Fig. 4a; arrow), which is an established threshold value for go/no-go tasks and corresponds to a d′ of 1.8 when the false alarm rates are low (≤3.8%) (Klump and Baur 1990; Dooling and Okanoya 1995). This procedure allowed us to determine the critical stimulus degradation above which the males ceased to turn, implying that signal recognition was severely impaired (Ronacher et al. 2000).


Neuronal precision and the limits for acoustic signal recognition in a small neuronal network.

Neuhofer D, Stemmler M, Ronacher B - J. Comp. Physiol. A Neuroethol. Sens. Neural. Behav. Physiol. (2010)

Robustness of signal recognition measured in behavioral tests with degraded female songs. a Phonotaxis responses of seven male grasshoppers. Abscissa: degradation levels in dB; ‘n’ indicates pure noise. Ordinate: the percentage of phonotactic turning responses; 100% means that the male reacted to every stimulus presentation. Behavioral critical degradation levels (bCDL) were determined at the intersection of each curve with the 50% response level (see arrow). b bCDL of 59 animals
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040818&req=5

Fig4: Robustness of signal recognition measured in behavioral tests with degraded female songs. a Phonotaxis responses of seven male grasshoppers. Abscissa: degradation levels in dB; ‘n’ indicates pure noise. Ordinate: the percentage of phonotactic turning responses; 100% means that the male reacted to every stimulus presentation. Behavioral critical degradation levels (bCDL) were determined at the intersection of each curve with the 50% response level (see arrow). b bCDL of 59 animals
Mentions: Males of C. biguttulus were used for the behavioral tests, in which the same stimuli were used as in electrophysiology. The playback experiments were performed at 30 ± 2°C in an anechoic chamber. Whenever a male started to sing, a model song was broadcast from a loudspeaker situated laterally. Each song was presented at least 10 times in pseudo-random order at an intensity of 60 dB SPL. The phonotactic behavior of the animal, whether it turned towards the loudspeaker or not, was monitored visually and journalized. The response probability to the different types of song models was calculated as the percentage of turning responses relative to the total number of stimulus presentations. We interpolated the degradation level that caused a decrease of turning response to 50% (Fig. 4a; arrow), which is an established threshold value for go/no-go tasks and corresponds to a d′ of 1.8 when the false alarm rates are low (≤3.8%) (Klump and Baur 1990; Dooling and Okanoya 1995). This procedure allowed us to determine the critical stimulus degradation above which the males ceased to turn, implying that signal recognition was severely impaired (Ronacher et al. 2000).

Bottom Line: By progressively corrupting the envelope of a female song, we determined the critical degradation level at which males failed to recognize a courtship call in behavioral experiments.At consecutive levels of processing, intrinsic variability increased, while the sensitivity to external noise decreased.We followed two approaches to determine critical degradation levels from spike train dissimilarities, and compared the results with the limits of signal recognition measured in behaving animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Humboldt-Universität zu Berlin, Invalidenstrasse 43, 10115, Berlin, Germany. neuhofda@cms.hu-berlin.de

ABSTRACT
Recognition of acoustic signals may be impeded by two factors: extrinsic noise, which degrades sounds before they arrive at the receiver's ears, and intrinsic neuronal noise, which reveals itself in the trial-to-trial variability of the responses to identical sounds. Here we analyzed how these two noise sources affect the recognition of acoustic signals from potential mates in grasshoppers. By progressively corrupting the envelope of a female song, we determined the critical degradation level at which males failed to recognize a courtship call in behavioral experiments. Using the same stimuli, we recorded intracellularly from auditory neurons at three different processing levels, and quantified the corresponding changes in spike train patterns by a spike train metric, which assigns a distance between spike trains. Unexpectedly, for most neurons, intrinsic variability accounted for the main part of the metric distance between spike trains, even at the strongest degradation levels. At consecutive levels of processing, intrinsic variability increased, while the sensitivity to external noise decreased. We followed two approaches to determine critical degradation levels from spike train dissimilarities, and compared the results with the limits of signal recognition measured in behaving animals.

Show MeSH