Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3PT Oxford, United Kingdom
Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3PT Oxford, United Kingdom.
Proc Natl Acad Sci U S A. 2020 Nov 10;117(45):28442-28451. doi: 10.1073/pnas.1922033117. Epub 2020 Oct 23.
Sounds are processed by the ear and central auditory pathway. These processing steps are biologically complex, and many aspects of the transformation from sound waveforms to cortical response remain unclear. To understand this transformation, we combined models of the auditory periphery with various encoding models to predict auditory cortical responses to natural sounds. The cochlear models ranged from detailed biophysical simulations of the cochlea and auditory nerve to simple spectrogram-like approximations of the information processing in these structures. For three different stimulus sets, we tested the capacity of these models to predict the time course of single-unit neural responses recorded in ferret primary auditory cortex. We found that simple models based on a log-spaced spectrogram with approximately logarithmic compression perform similarly to the best-performing biophysically detailed models of the auditory periphery, and more consistently well over diverse natural and synthetic sounds. Furthermore, we demonstrated that including approximations of the three categories of auditory nerve fiber in these simple models can substantially improve prediction, particularly when combined with a network encoding model. Our findings imply that the properties of the auditory periphery and central pathway may together result in a simpler than expected functional transformation from ear to cortex. Thus, much of the detailed biological complexity seen in the auditory periphery does not appear to be important for understanding the cortical representation of sound.
声音由耳朵和中枢听觉通路处理。这些处理步骤在生物学上非常复杂，声音波形到皮质反应的转换的许多方面仍然不清楚。为了理解这种转换，我们将听觉外围模型与各种编码模型相结合，以预测对自然声音的听觉皮质反应。耳蜗模型从耳蜗和听神经的详细生物物理模拟到这些结构中信息处理的简单频谱图样近似不等。对于三个不同的刺激集，我们测试了这些模型预测雪貂初级听觉皮层中记录的单个神经元反应时程的能力。我们发现，基于对数间距频谱图且具有近似对数压缩的简单模型与听觉外围的表现最佳的详细生物物理模型性能相当，并且在各种自然和合成声音上的表现更为一致。此外，我们证明，在这些简单模型中包含对三类听神经纤维的近似值可以大大提高预测能力，尤其是与网络编码模型结合使用时。我们的研究结果表明，听觉外围和中枢通路的特性可能共同导致从耳朵到大脑皮层的功能转换比预期的更简单。因此，在听觉外围中看到的许多详细的生物学复杂性似乎对于理解声音的皮质表示并不重要。
