Spatial release from masking (SRM) occurs when spatial separation between a signal and masker decreases masked thresholds. The mechanically-coupled ears of Ormia ochracea are specialized for hyperacute directional hearing, but the possible role of SRM, or whether such specializations exhibit limitations for sound source segregation, is unknown. We recorded phonotaxis to a cricket song masked by band-limited noise. With a masker, response thresholds increased and localization was diverted away from the signal and masker. Increased separation from 6° to 90° did not decrease response thresholds or improve localization accuracy, thus SRM does not operate in this range of spatial separations. Tympanal vibrations and auditory nerve responses reveal that localization errors were consistent with changes in peripheral coding of signal location and flies localized towards the ear with better signal detection. Our results demonstrate that, in a mechanically coupled auditory system, specialization for directional hearing does not contribute to source segregation.
Translational velocity in response to the target signal and masker presented alone
Masker presentation started and ended 0.5 and 4.5 seconds after the onset of data acquisition respectively. Signal presentation started and ended 1.0 and 4.0 seconds after the onset of data acquisition, respectively. Data plotted in figure 2A.
Figure_2 - source data 1.xlsx
Steering velocity in response to the target signal and noise alone
Masker presentation started and ended 0.5 and 4.5 seconds after the onset of data acquisition respectively. Signal presentation started and ended 1.0 and 4.0 seconds after the onset of data acquisition, respectively. Data plotted in figure 2B.
Figure_2 - source data 2.xlsx
Virtual walking path in response to the target signal and masker presented alone
‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 2C.
Figure_2 - source data 3.xlsx
Behavioral response thresholds in response to a target signal in quiet, spatially grouped, and separated signal and masker
Data plotted in figure 3.
Figure_3 - source data 1.xlsx
Translational velocity in response to spatially grouped target signal and masker presented at different signal-to-noise ratios (SNRs)
The target signal was presented at 76 dB SPL while the masker intensity was varied to achieve three SNRs (-6, 0, +6 dB). Masker presentation started and ended 0.5 and 4.5 seconds after the onset of data acquisition respectively. Signal presentation started and ended 1.0 and 4.0 seconds after the onset of data acquisition, respectively. Data plotted in figure 4A (left).
Figure 4 - source data 1.xlsx
Steering velocity in response to spatially grouped target signal and masker presented at different signal-to-noise ratios (SNRs)
The target signal was presented at 76 dB SPL while the masker intensity was varied to achieve three SNRs (-6, 0, +6 dB). Masker presentation started and ended 0.5 and 4.5 seconds after the onset of data acquisition respectively. Signal presentation started and ended 1.0 and 4.0 seconds after the onset of data acquisition, respectively. Data plotted in figure 4B (left).
Figure 4 - source data 2.xlsx
Virtual walking path in response spatially grouped target signal and masker presented at different signal-to-noise ratios (SNRs).
The target signal was presented at 76 dB SPL while the masker intensity was varied to achieve three SNRs (-6, 0, +6 dB). ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 4C (left).
Figure 4 - source data 3.xlsx
Translational velocity in response to spatially separated target signal and masker presented at different signal-to-noise ratios (SNRs).
The target signal was presented at 76 dB SPL while the masker intensity was varied to achieve three SNRs (-6, 0, +6 dB). Masker presentation started and ended 0.5 and 4.5 seconds after the onset of data acquisition respectively. Signal presentation started and ended 1.0 and 4.0 seconds after the onset of data acquisition, respectively. Data plotted in figure 4A (right).
Figure 4 - source data 4.xlsx
Steering velocity in response to spatially separated target signal and masker presented at different signal-to-noise ratios (SNRs)
The target signal was presented at 76 dB SPL while the masker intensity was varied to achieve three SNRs (-6, 0, +6 dB). Masker presentation started and ended 0.5 and 4.5 seconds after the onset of data acquisition respectively. Signal presentation started and ended 1.0 and 4.0 seconds after the onset of data acquisition, respectively. Data plotted in figure 4B (right).
Figure 4 - source data 5.xlsx
Virtual walking path in response to spatially separated target signal and masker presented at different signal-to-noise ratios (SNRs).
The target signal was presented at 76 dB SPL while the masker intensity was varied to achieve three SNRs (-6, 0, +6 dB). ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 4C (right).
Figure 4 - source data 6.xlsx
Virtual walking path in response to the target signal presented in isolation.
The target signal was presented at 76 dB SPL from a forward speaker. ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 5A.
Figure_5- source data 1.xlsx
Virtual walking path in response to spatially grouped target signal and masker presented at equal intensity.
The target signal was presented at 76 dB SPL from a forward speaker while the masker was presented at the same intensity from an adjacent speaker to the right. ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 5B.
Figure_5- source data 2.xlsx
Virtual walking path in response to spatially grouped target signal and masker presented at equal intensity.
The target signal was presented at 76 dB SPL from a forward speaker while the masker was presented at the same intensity from an adjacent speaker to the left. ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 5C.
Figure_5- source data 3.xlsx
Virtual walking path in response to spatially grouped target signal and maskers presented at equal intensity.
The target signal was presented at 76 dB SPL from a forward speaker while two coherent maskers were presented at the same combined intensity from adjacent speakers to the left and right of the signal speaker. ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 5D.
Figure_5- source data 4.xlsx
Virtual walking path in response to spatially separated target signal and masker presented at equal intensity
The target signal was presented at 76 dB SPL from a forward speaker while the masker was presented at the same intensity from a lateral speaker to the right. ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 5E.
Figure_5- source data 5.xlsx
Virtual walking path in response to spatially separated target signal and masker presented at equal intensity
The target signal was presented at 76 dB SPL from a forward speaker while the masker was presented at the same intensity from a lateral speaker to the left. ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 5F.
Figure_5- source data 6.xlsx
Virtual walking path in response to spatially grouped target signal and maskers presented at equal intensity
The target signal was presented at 76 dB SPL from a forward speaker while two coherent maskers werepresented at the same combined intensity from lateral speakers to the left and right of the signal speaker. ‘X’ and ‘Y’ coordinates of virtual walking paths measured from the trackball system. Data plotted in figure 5G.
Figure_5- source data 7.xlsx
Raw traces of tympanal vibration in response to combined signal and masker under conditions of masker source located near (grouped) or far (separated) from signal source.
Ipsi- and contralateral refer to the masker. Signal pulses were repeated at 400 ms intervals during continuous masker broadcast.
Figure 6 - source data 1.xlsx
Normalized-amplitude tympanal vibration responses
Vibration measurements are normalized to the peak response in response to the target signal. Data plotted in figure 6B, C.
Figure 6 - source data 2.xlsx
Smoothed tympanal vibration responses.
Measurements smoothed with a 2000-point sliding rms window.
Figure 6 - source data 3.xlsx
Effective amplitude measurements
Effective amplitude measurements (i.e. within-trace signal-to-noise ratio) from smoothed tympanal responses for 23 iterations of signal within the masker. Signal amplitudes were measured from 30 ms time segments corresponding with signal pulses; masker amplitudes were measured from 30 ms segments in the middle of the interpulse interval (i.e. 200 ms after signal-pulse onset). Data plotted in figure 6D.
Figure 6 - source data 4.xlsx
Raw laser vibrometry measurements from the masker ipsi- and contralateral ears in response to spatially separated target signal and masker at varied signal-to-noise ratios (SNRs)
The target signal was broadcast from the forward location at 76 dB SPL while the masker was broadcast from a lateral position at varied intensities to achieve three SNRs (-6, 0, +6 dB). Data from different flies are found as separate Excel sheets within the data file. Effected amplitude measurements derived from the raw data are plotted in figure 7A.
Figure 7 – Source data 2. Mid-angular headings from behavioural experiments. Excel file include responses to a 76 dB SPL target signal broadcast alone from the forward speaker, a masker broadcast alone from the forward speaker, and the 76 dB SPL target signal and masker broadcast at varied signal-to-noise ratios (-6, 0, +6 dB) from spatially grouped or separated speakers. Data plotted in figure 7C.
figure_7 - source data 1.xlsx
Mid-angular headings from behavioural experiments.
Excel file include responses to a 76 dB SPL target signal broadcast alone from the forward speaker, a masker broadcast alone from the forward speaker, and the 76 dB SPL target signal and masker broadcast at varied signal-to-noise ratios (-6, 0, +6 dB) from spatially grouped or separated speakers. Data plotted in figure 7C.
figure_7 - source data 2.xlsx
Root Mean Square (RMS) values calculated from multiunit recordings of left and right auditory nerve.
RMS calculated over 40 ms time segments during an interval with a target signal and a spatially separated masker broadcast at varied signal-to-noise ratios (-18, -12, -6, 0, +6 dB), and an equivalent time window during masker broadcast alone. Signal detection theory was applied to RMS measurements to masked thresholds for the masker ipsi- and contralateral ears. These data are plotted in figure 8C.
figure_8 - source data 1.xlsx
