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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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Proportions of trials on which saccades were lag-directed for three birds.(A) Proportion of lag-directed saccades in the standard paradigm plotted against the lead/lag delay. The black, dashed, line in this and other plots shows the average of all three subjects. (B) Proportion of lag-directed saccades observed 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 (onset-delay). The number underneath indicates the length of the lag-alone segment. (C) Proportion of lag-directed saccades observed when lag-alone segments were experimentally shortened. (D) Proportions of lag-directed saccades shown here have been regrouped so that the length of the lag-alone segment is constant within each panel.
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pone-0003598-g006: Proportions of trials on which saccades were lag-directed for three birds.(A) Proportion of lag-directed saccades in the standard paradigm plotted against the lead/lag delay. The black, dashed, line in this and other plots shows the average of all three subjects. (B) Proportion of lag-directed saccades observed 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 (onset-delay). The number underneath indicates the length of the lag-alone segment. (C) Proportion of lag-directed saccades observed when lag-alone segments were experimentally shortened. (D) Proportions of lag-directed saccades shown here have been regrouped so that the length of the lag-alone segment is constant within each panel.

Mentions: Results are shown in Figure 6. Figure 6A plots the proportion of saccades for each bird to the lagging source, against delay, in the standard paradigm where the lead and lag sounds were of equal lengths (Fig. 1B). Consistent with the results of an earlier study [28], the proportion of lag-directed turns remained low for delays up to 6 ms and increased for delays of 12 or 24 ms.


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

Nelson BS, Takahashi TT - PLoS ONE (2008)

Proportions of trials on which saccades were lag-directed for three birds.(A) Proportion of lag-directed saccades in the standard paradigm plotted against the lead/lag delay. The black, dashed, line in this and other plots shows the average of all three subjects. (B) Proportion of lag-directed saccades observed 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 (onset-delay). The number underneath indicates the length of the lag-alone segment. (C) Proportion of lag-directed saccades observed when lag-alone segments were experimentally shortened. (D) Proportions of lag-directed saccades shown here have been regrouped so that the length of the lag-alone segment is constant within each panel.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2571984&req=5

pone-0003598-g006: Proportions of trials on which saccades were lag-directed for three birds.(A) Proportion of lag-directed saccades in the standard paradigm plotted against the lead/lag delay. The black, dashed, line in this and other plots shows the average of all three subjects. (B) Proportion of lag-directed saccades observed 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 (onset-delay). The number underneath indicates the length of the lag-alone segment. (C) Proportion of lag-directed saccades observed when lag-alone segments were experimentally shortened. (D) Proportions of lag-directed saccades shown here have been regrouped so that the length of the lag-alone segment is constant within each panel.
Mentions: Results are shown in Figure 6. Figure 6A plots the proportion of saccades for each bird to the lagging source, against delay, in the standard paradigm where the lead and lag sounds were of equal lengths (Fig. 1B). Consistent with the results of an earlier study [28], the proportion of lag-directed turns remained low for delays up to 6 ms and increased for delays of 12 or 24 ms.

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