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Independence of echo-threshold and echo-delay in the barn owl.

Nelson BS, Takahashi TT - PLoS ONE (2008)

Bottom Line: Under this paradigm, there were two possible stimulus segments that could potentially signal the location of the echo.By lengthening the echo's duration, independently of its delay, spikes and saccades were evoked by the source of the echo even at delays that normally evoked saccades to only the direct source.An echo's location thus appears to be signaled by the neural response evoked after the offset of the direct sound.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience, University of Oregon, Eugene, Oregon, USA. bsnelson@uoregon.edu

ABSTRACT
Despite their prevalence in nature, echoes are not perceived as events separate from the sounds arriving directly from an active source, until the echo's delay is long. We measured the head-saccades of barn owls and the responses of neurons in their auditory space-maps while presenting a long duration noise-burst and a simulated echo. Under this paradigm, there were two possible stimulus segments that could potentially signal the location of the echo. One was at the onset of the echo; the other, after the offset of the direct (leading) sound, when only the echo was present. By lengthening the echo's duration, independently of its delay, spikes and saccades were evoked by the source of the echo even at delays that normally evoked saccades to only the direct source. An echo's location thus appears to be signaled by the neural response evoked after the offset of the direct sound.

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Summary of overall neural responses to lead and lag targets.(A) Responses evoked in the standard paradigm in which lead-alone and lag-alone segments were of equal length. (B) Responses evoked when lag-alone segments were experimentally lengthened. At each point along the abscissa, the number on top indicates the length of the lead-alone segment. The number underneath indicates the length of the lag-alone segment. (C) Responses evoked when lag-alone segments were experimentally shortened. (D) Responses shown here have been regrouped so that the length of the lag-alone segment is constant within each panel. All data points represent the median number of spikes evoked when the target led (blue lines) or lagged (red lines). Thin lines indicate the first and third quartiles of each response. Each value is normalized to the average response evoked, in each cell, by 30 ms sounds (>50 repetitions) presented from the center of its SRF [11]. The dashed horizontal line represents the median response evoked by two, simultaneous, uncorrelated, noise-bursts from target and masker loci.
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pone-0003598-g004: Summary of overall neural responses to lead and lag targets.(A) Responses evoked in the standard paradigm in which lead-alone and lag-alone segments were of equal length. (B) Responses evoked when lag-alone segments were experimentally lengthened. At each point along the abscissa, the number on top indicates the length of the lead-alone segment. The number underneath indicates the length of the lag-alone segment. (C) Responses evoked when lag-alone segments were experimentally shortened. (D) Responses shown here have been regrouped so that the length of the lag-alone segment is constant within each panel. All data points represent the median number of spikes evoked when the target led (blue lines) or lagged (red lines). Thin lines indicate the first and third quartiles of each response. Each value is normalized to the average response evoked, in each cell, by 30 ms sounds (>50 repetitions) presented from the center of its SRF [11]. The dashed horizontal line represents the median response evoked by two, simultaneous, uncorrelated, noise-bursts from target and masker loci.

Mentions: Figure 4A shows the median responses evoked in our sample of 39 neurons in the standard paradigm where the lengths of the lead-alone and lag-alone segments were equal and when the target led (blue lines) or lagged (red lines; Fig. 1B). Leading targets evoked stronger responses than lagging targets and both responses increased with delay, as earlier studies have shown [8]–[15], [17].


Independence of echo-threshold and echo-delay in the barn owl.

Nelson BS, Takahashi TT - PLoS ONE (2008)

Summary of overall neural responses to lead and lag targets.(A) Responses evoked in the standard paradigm in which lead-alone and lag-alone segments were of equal length. (B) Responses evoked when lag-alone segments were experimentally lengthened. At each point along the abscissa, the number on top indicates the length of the lead-alone segment. The number underneath indicates the length of the lag-alone segment. (C) Responses evoked when lag-alone segments were experimentally shortened. (D) Responses shown here have been regrouped so that the length of the lag-alone segment is constant within each panel. All data points represent the median number of spikes evoked when the target led (blue lines) or lagged (red lines). Thin lines indicate the first and third quartiles of each response. Each value is normalized to the average response evoked, in each cell, by 30 ms sounds (>50 repetitions) presented from the center of its SRF [11]. The dashed horizontal line represents the median response evoked by two, simultaneous, uncorrelated, noise-bursts from target and masker loci.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2571984&req=5

pone-0003598-g004: Summary of overall neural responses to lead and lag targets.(A) Responses evoked in the standard paradigm in which lead-alone and lag-alone segments were of equal length. (B) Responses evoked when lag-alone segments were experimentally lengthened. At each point along the abscissa, the number on top indicates the length of the lead-alone segment. The number underneath indicates the length of the lag-alone segment. (C) Responses evoked when lag-alone segments were experimentally shortened. (D) Responses shown here have been regrouped so that the length of the lag-alone segment is constant within each panel. All data points represent the median number of spikes evoked when the target led (blue lines) or lagged (red lines). Thin lines indicate the first and third quartiles of each response. Each value is normalized to the average response evoked, in each cell, by 30 ms sounds (>50 repetitions) presented from the center of its SRF [11]. The dashed horizontal line represents the median response evoked by two, simultaneous, uncorrelated, noise-bursts from target and masker loci.
Mentions: Figure 4A shows the median responses evoked in our sample of 39 neurons in the standard paradigm where the lengths of the lead-alone and lag-alone segments were equal and when the target led (blue lines) or lagged (red lines; Fig. 1B). Leading targets evoked stronger responses than lagging targets and both responses increased with delay, as earlier studies have shown [8]–[15], [17].

Bottom Line: Under this paradigm, there were two possible stimulus segments that could potentially signal the location of the echo.By lengthening the echo's duration, independently of its delay, spikes and saccades were evoked by the source of the echo even at delays that normally evoked saccades to only the direct source.An echo's location thus appears to be signaled by the neural response evoked after the offset of the direct sound.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience, University of Oregon, Eugene, Oregon, USA. bsnelson@uoregon.edu

ABSTRACT
Despite their prevalence in nature, echoes are not perceived as events separate from the sounds arriving directly from an active source, until the echo's delay is long. We measured the head-saccades of barn owls and the responses of neurons in their auditory space-maps while presenting a long duration noise-burst and a simulated echo. Under this paradigm, there were two possible stimulus segments that could potentially signal the location of the echo. One was at the onset of the echo; the other, after the offset of the direct (leading) sound, when only the echo was present. By lengthening the echo's duration, independently of its delay, spikes and saccades were evoked by the source of the echo even at delays that normally evoked saccades to only the direct source. An echo's location thus appears to be signaled by the neural response evoked after the offset of the direct sound.

Show MeSH