Cluster of Excellence "Hearing4all" and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany.
Department of Biomedical Engineering, University of Rochester, Rochester, New York, USA.
Eur J Neurosci. 2022 Aug;56(3):4060-4085. doi: 10.1111/ejn.15744. Epub 2022 Jul 1.
Schroeder-phase harmonic tone complexes have been used in physiological and psychophysical studies in several species to gain insight into cochlear function. Each pitch period of the Schroeder stimulus contains a linear frequency sweep; the duty cycle, sweep velocity, and direction are controlled by parameters of the phase spectrum. Here, responses to a range of Schroeder-phase harmonic tone complexes were studied both behaviorally and in neural recordings from the auditory nerve and inferior colliculus of Mongolian gerbils. Gerbils were able to discriminate Schroeder-phase harmonic tone complexes based on sweep direction, duty cycle, and/or velocity for fundamental frequencies up to 200 Hz. Temporal representation in neural responses based on the van Rossum spike-distance metric, with time constants of either 1 ms or related to the stimulus' period, was compared with average discharge rates. Neural responses and behavioral performance were both expressed in terms of sensitivity, d', to allow direct comparisons. Our results suggest that in the auditory nerve, stimulus fine structure is represented by spike timing, whereas envelope is represented by rate. In the inferior colliculus, both temporal fine structure and envelope appear to be represented best by rate. However, correlations between neural d' values and behavioral sensitivity for sweep direction were strongest for both temporal metrics, for both auditory nerve and inferior colliculus. Furthermore, the high sensitivity observed in the inferior colliculus neural rate-based discrimination suggests that these neurons integrate across multiple inputs arising from the auditory periphery.
施罗德相位谐波复合音在多个物种的生理和心理物理研究中被用来深入了解耳蜗功能。施罗德刺激的每个音周期包含一个线性频率扫描；占空比、扫描速度和方向由相位谱的参数控制。在这里，研究了从听觉神经和蒙古沙鼠的下丘记录的一系列施罗德相位谐波复合音的反应。沙鼠能够根据扫频方向、占空比和/或速度辨别施罗德相位谐波复合音，其基频高达 200 Hz。基于 van Rossum 尖峰距离度量的神经反应的时间表示，其时间常数为 1 ms 或与刺激的周期相关，与平均放电率进行了比较。神经反应和行为表现都以灵敏度 d'来表示，以便进行直接比较。我们的结果表明，在听觉神经中，刺激的精细结构由尖峰时间表示，而包络由速率表示。在下丘，时间精细结构和包络似乎都由速率表示最佳。然而，对于两种时间度量，无论是听觉神经还是下丘，神经 d'值与行为灵敏度之间的相关性最强的是扫频方向。此外，在下丘神经基于速率的辨别中观察到的高灵敏度表明这些神经元整合了来自听觉外围的多个输入。
