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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 neural responses evoked during the lead-alone, lag-alone, and superposed segments.(A) Responses evoked during the lead-alone (open, blue, squares) and lag-alone (closed, red, squares) segments. Each data point represents the median number of spikes, normalized to the average response evoked, in each cell, by 30 ms sounds (>50 repetitions) presented from the center of its SRF [11]. Vertical lines indicate the first and third quartiles of each response. The upper row of numbers along the abscissa represents the onset-delay and the bottom row represents the length of each segment. (B) Responses evoked during the superposed segments when the target led (open, blue, squares) or lagged (closed, red, squares). Responses evoked by two, simultaneous, uncorrelated, noise-bursts from the target and masker loci are indicated by black diamonds (A,B). Note that the ordinate axis in panel B is expanded relative to that of panel A.
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pone-0003598-g003: Summary of neural responses evoked during the lead-alone, lag-alone, and superposed segments.(A) Responses evoked during the lead-alone (open, blue, squares) and lag-alone (closed, red, squares) segments. Each data point represents the median number of spikes, normalized to the average response evoked, in each cell, by 30 ms sounds (>50 repetitions) presented from the center of its SRF [11]. Vertical lines indicate the first and third quartiles of each response. The upper row of numbers along the abscissa represents the onset-delay and the bottom row represents the length of each segment. (B) Responses evoked during the superposed segments when the target led (open, blue, squares) or lagged (closed, red, squares). Responses evoked by two, simultaneous, uncorrelated, noise-bursts from the target and masker loci are indicated by black diamonds (A,B). Note that the ordinate axis in panel B is expanded relative to that of panel A.

Mentions: The recovery of neuronal responses to lagging sound sources has typically been attributed to the onset-delay [8]–[15], which, in our paradigm, is equal to the length of the lead-alone segment. The alternative hypothesis is that the lag-alone segment accounts for this recovery. Responses evoked during the lag-alone and superposed segments are plotted against delay in Figure 3 (red, filled, markers) to determine, quantitatively, which segment best accounts for the recovery to the lag source. Responses evoked during lag-alone segments increased significantly with delay (Fig. 3A; lead: P<1⋅10−6; lag: P<1⋅10−6; df = 4; Kruskal-Wallis). In contrast, responses evoked during superposed segments did not vary significantly with delay (Fig. 3B; lead: P = 0.053; lag: P = 0.16, df = 4; Kruskal-Wallis). Furthermore, they did not differ from the responses evoked by two, simultaneous, uncorrelated, noise-bursts (black diamond, Fig. 3B; lead: P = 0.068; lag: P = 0.24, df = 4; Kruskal-Wallis) suggesting that the decrease in firing rate during the superposed segment can be explained by binaural decorrelation, and that inhibition need not be invoked. Taken together, the observations above are inconsistent with the idea that the delay, per se, accounts for the neuronal recovery. Instead, the recovery is best attributed to the lag-alone segment.


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

Nelson BS, Takahashi TT - PLoS ONE (2008)

Summary of neural responses evoked during the lead-alone, lag-alone, and superposed segments.(A) Responses evoked during the lead-alone (open, blue, squares) and lag-alone (closed, red, squares) segments. Each data point represents the median number of spikes, normalized to the average response evoked, in each cell, by 30 ms sounds (>50 repetitions) presented from the center of its SRF [11]. Vertical lines indicate the first and third quartiles of each response. The upper row of numbers along the abscissa represents the onset-delay and the bottom row represents the length of each segment. (B) Responses evoked during the superposed segments when the target led (open, blue, squares) or lagged (closed, red, squares). Responses evoked by two, simultaneous, uncorrelated, noise-bursts from the target and masker loci are indicated by black diamonds (A,B). Note that the ordinate axis in panel B is expanded relative to that of panel A.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2571984&req=5

pone-0003598-g003: Summary of neural responses evoked during the lead-alone, lag-alone, and superposed segments.(A) Responses evoked during the lead-alone (open, blue, squares) and lag-alone (closed, red, squares) segments. Each data point represents the median number of spikes, normalized to the average response evoked, in each cell, by 30 ms sounds (>50 repetitions) presented from the center of its SRF [11]. Vertical lines indicate the first and third quartiles of each response. The upper row of numbers along the abscissa represents the onset-delay and the bottom row represents the length of each segment. (B) Responses evoked during the superposed segments when the target led (open, blue, squares) or lagged (closed, red, squares). Responses evoked by two, simultaneous, uncorrelated, noise-bursts from the target and masker loci are indicated by black diamonds (A,B). Note that the ordinate axis in panel B is expanded relative to that of panel A.
Mentions: The recovery of neuronal responses to lagging sound sources has typically been attributed to the onset-delay [8]–[15], which, in our paradigm, is equal to the length of the lead-alone segment. The alternative hypothesis is that the lag-alone segment accounts for this recovery. Responses evoked during the lag-alone and superposed segments are plotted against delay in Figure 3 (red, filled, markers) to determine, quantitatively, which segment best accounts for the recovery to the lag source. Responses evoked during lag-alone segments increased significantly with delay (Fig. 3A; lead: P<1⋅10−6; lag: P<1⋅10−6; df = 4; Kruskal-Wallis). In contrast, responses evoked during superposed segments did not vary significantly with delay (Fig. 3B; lead: P = 0.053; lag: P = 0.16, df = 4; Kruskal-Wallis). Furthermore, they did not differ from the responses evoked by two, simultaneous, uncorrelated, noise-bursts (black diamond, Fig. 3B; lead: P = 0.068; lag: P = 0.24, df = 4; Kruskal-Wallis) suggesting that the decrease in firing rate during the superposed segment can be explained by binaural decorrelation, and that inhibition need not be invoked. Taken together, the observations above are inconsistent with the idea that the delay, per se, accounts for the neuronal recovery. Instead, the recovery is best attributed to the lag-alone segment.

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