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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Stimuli and principle of data evaluation. a The upper panel shows the oscillogram of the original female song which contained 12 similar syllables (s) separated by pauses (p); each syllable consisted of six sound pulses (see enlargement). Lower panel the envelope of two song syllables before and after the addition of envelope noise at −3 and 3 dB NSR. b Amplitude spectra of the song envelopes shown in a (amplitude in arbitrary units). c Examples of spike train patterns in response to 12 syllables of a female grasshopper call for various levels of noise. Upper panel the spike responses of TN1, a tonic local interneuron. Lower panel AN12, a phasic ascending neuron. d Distance matrix of the spike trains of TN1. Metric distances between spike trains are color coded from blue to red (zero to maximum distance in percent). Square blocks along the diagonal contain the ‘intrinsic’ distance values for each degradation level (e.g. x0 distances between spike trains in response to the original song). Squares along the right column indicate ‘extrinsic’ distance values (e.g. y1 the distances between spike trains in response to the original song and the first degradation level)
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Fig1: Stimuli and principle of data evaluation. a The upper panel shows the oscillogram of the original female song which contained 12 similar syllables (s) separated by pauses (p); each syllable consisted of six sound pulses (see enlargement). Lower panel the envelope of two song syllables before and after the addition of envelope noise at −3 and 3 dB NSR. b Amplitude spectra of the song envelopes shown in a (amplitude in arbitrary units). c Examples of spike train patterns in response to 12 syllables of a female grasshopper call for various levels of noise. Upper panel the spike responses of TN1, a tonic local interneuron. Lower panel AN12, a phasic ascending neuron. d Distance matrix of the spike trains of TN1. Metric distances between spike trains are color coded from blue to red (zero to maximum distance in percent). Square blocks along the diagonal contain the ‘intrinsic’ distance values for each degradation level (e.g. x0 distances between spike trains in response to the original song). Squares along the right column indicate ‘extrinsic’ distance values (e.g. y1 the distances between spike trains in response to the original song and the first degradation level)

Mentions: We tested to what degree extrinsic and intrinsic noise affect the neuronal representation of sound patterns by successively degrading the envelope of a well-accepted female song with random amplitude fluctuations (Fig. 1a). The original and the degraded stimuli were then used both in behavioral experiments and during in vivo neurophysiological recordings from the metathoracic ganglion. The metathoracic ganglion houses an important stage of auditory information processing, comparable to the auditory brain stem nuclei of vertebrates (Stumpner and Ronacher 1994). More than 50 receptor neurons per ear converge onto 10–15 local interneurons that are connected to 15–20 ascending interneurons (Römer and Marquart 1984; Stumpner and Ronacher 1991) which carry the auditory information to the brain. We recorded spike trains from identified neurons belonging to these stages of auditory processing. Distinct cell types could be identified as individuals on the basis of their characteristic morphology and physiology.Fig. 1


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)

Stimuli and principle of data evaluation. a The upper panel shows the oscillogram of the original female song which contained 12 similar syllables (s) separated by pauses (p); each syllable consisted of six sound pulses (see enlargement). Lower panel the envelope of two song syllables before and after the addition of envelope noise at −3 and 3 dB NSR. b Amplitude spectra of the song envelopes shown in a (amplitude in arbitrary units). c Examples of spike train patterns in response to 12 syllables of a female grasshopper call for various levels of noise. Upper panel the spike responses of TN1, a tonic local interneuron. Lower panel AN12, a phasic ascending neuron. d Distance matrix of the spike trains of TN1. Metric distances between spike trains are color coded from blue to red (zero to maximum distance in percent). Square blocks along the diagonal contain the ‘intrinsic’ distance values for each degradation level (e.g. x0 distances between spike trains in response to the original song). Squares along the right column indicate ‘extrinsic’ distance values (e.g. y1 the distances between spike trains in response to the original song and the first degradation level)
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040818&req=5

Fig1: Stimuli and principle of data evaluation. a The upper panel shows the oscillogram of the original female song which contained 12 similar syllables (s) separated by pauses (p); each syllable consisted of six sound pulses (see enlargement). Lower panel the envelope of two song syllables before and after the addition of envelope noise at −3 and 3 dB NSR. b Amplitude spectra of the song envelopes shown in a (amplitude in arbitrary units). c Examples of spike train patterns in response to 12 syllables of a female grasshopper call for various levels of noise. Upper panel the spike responses of TN1, a tonic local interneuron. Lower panel AN12, a phasic ascending neuron. d Distance matrix of the spike trains of TN1. Metric distances between spike trains are color coded from blue to red (zero to maximum distance in percent). Square blocks along the diagonal contain the ‘intrinsic’ distance values for each degradation level (e.g. x0 distances between spike trains in response to the original song). Squares along the right column indicate ‘extrinsic’ distance values (e.g. y1 the distances between spike trains in response to the original song and the first degradation level)
Mentions: We tested to what degree extrinsic and intrinsic noise affect the neuronal representation of sound patterns by successively degrading the envelope of a well-accepted female song with random amplitude fluctuations (Fig. 1a). The original and the degraded stimuli were then used both in behavioral experiments and during in vivo neurophysiological recordings from the metathoracic ganglion. The metathoracic ganglion houses an important stage of auditory information processing, comparable to the auditory brain stem nuclei of vertebrates (Stumpner and Ronacher 1994). More than 50 receptor neurons per ear converge onto 10–15 local interneurons that are connected to 15–20 ascending interneurons (Römer and Marquart 1984; Stumpner and Ronacher 1991) which carry the auditory information to the brain. We recorded spike trains from identified neurons belonging to these stages of auditory processing. Distinct cell types could be identified as individuals on the basis of their characteristic morphology and physiology.Fig. 1

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
Related in: MedlinePlus