Data from: How spatial release from masking may fail to function in a highly directional auditory system

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.空间掩蔽释放（Spatial release from masking，SRM）指当信号与掩蔽声的空间间距缩小时，掩蔽阈值降低的现象。奥米亚寄蝇（Ormia ochracea）的机械耦合式听觉器官特化出超敏锐的定向听觉能力，但SRM在其中可能发挥的作用，以及这类特化是否存在声源分离的局限性，目前仍属未知。我们记录了被限带噪声掩蔽的蟋蟀鸣曲所引发的趋声行为。当存在掩蔽声时，趋声反应的阈值升高，且声源定位方向偏离信号与掩蔽声的原本位置。当空间间距从6°增大至90°时，反应阈值未出现降低，定位精度也未得到提升，因此SRM在该空间间距范围内并未发挥作用。鼓膜振动与听神经反应的实验结果表明，定位误差与信号位置的外周编码变化相一致，且寄生蝇会朝向信号检测效果更优的一侧听觉器官进行定位。本研究结果证实，在机械耦合式听觉系统中，定向听觉的特化能力并不能助力声源分离。