Unit of Audiology, Department of Clinical Science, Intervention and Technology, Karolinska InstitutetStockholm, Sweden.
Institut Pasteur, Unité de Génétique et Physiologie de l'AuditionParis, France.
Front Neural Circuits. 2017 May 31;11:37. doi: 10.3389/fncir.2017.00037. eCollection 2017.
Auditory streaming enables perception and interpretation of complex acoustic environments that contain competing sound sources. At early stages of central processing, sounds are segregated into separate streams representing attributes that later merge into acoustic objects. Streaming of temporal cues is critical for perceiving vocal communication, such as human speech, but our understanding of circuits that underlie this process is lacking, particularly at subcortical levels. The superior paraolivary nucleus (SPON), a prominent group of inhibitory neurons in the mammalian brainstem, has been implicated in processing temporal information needed for the segmentation of ongoing complex sounds into discrete events. The SPON requires temporally precise and robust excitatory input(s) to convey information about the steep rise in sound amplitude that marks the onset of voiced sound elements. Unfortunately, the sources of excitation to the SPON and the impact of these inputs on the behavior of SPON neurons have yet to be resolved. Using anatomical tract tracing and immunohistochemistry, we identified octopus cells in the contralateral cochlear nucleus (CN) as the primary source of excitatory input to the SPON. Cluster analysis of miniature excitatory events also indicated that the majority of SPON neurons receive one type of excitatory input. Precise octopus cell-driven onset spiking coupled with transient offset spiking make SPON responses well-suited to signal transitions in sound energy contained in vocalizations. Targets of octopus cell projections, including the SPON, are strongly implicated in the processing of temporal sound features, which suggests a common pathway that conveys information critical for perception of complex natural sounds.
听觉流使人们能够感知和解释包含竞争声源的复杂声学环境。在中枢处理的早期阶段，声音被分离成代表属性的单独流，这些属性稍后会合并为声学对象。时间线索的流分离对于感知语音交流（如人类言语）至关重要，但我们对这种过程背后的电路的理解却很缺乏，特别是在皮质下水平。上橄榄核复合体（SPON）是哺乳动物脑干中一组突出的抑制性神经元，它参与处理时间信息，这些信息对于将持续的复杂声音分割为离散事件是必需的。SPON 需要时间上精确和强大的兴奋性输入，以传递关于声音幅度急剧上升的信息，该信息标志着浊音声音元素的开始。不幸的是，SPON 的兴奋源以及这些输入对 SPON 神经元行为的影响尚未得到解决。使用解剖学束追踪和免疫组织化学，我们确定了对侧耳蜗核（CN）中的八爪鱼细胞是 SPON 的主要兴奋性输入源。微型兴奋性事件的聚类分析还表明，大多数 SPON 神经元接收一种类型的兴奋性输入。精确的八爪鱼细胞驱动的起始尖峰伴随着短暂的偏移尖峰，使 SPON 反应非常适合包含在语音中的声音能量的信号转换。八爪鱼细胞投射的目标，包括 SPON，强烈暗示了时间声音特征的处理，这表明了一种传递对感知复杂自然声音至关重要的信息的共同途径。
