Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7070, USA.
J Neurosci. 2013 Jan 23;33(4):1598-614. doi: 10.1523/JNEUROSCI.2541-12.2013.
The acoustic environment contains biologically relevant information on timescales from microseconds to tens of seconds. The auditory brainstem nuclei process this temporal information through parallel pathways that originate in the cochlear nucleus from different classes of cells. Although the roles of ion channels and excitatory synapses in temporal processing have been well studied, the contribution of inhibition is less well understood. Here, we show in CBA/CaJ mice that the two major projection neurons of the ventral cochlear nucleus, the bushy and T-stellate cells, receive glycinergic inhibition with different synaptic conductance time courses. Bushy cells, which provide precisely timed spike trains used in sound localization and pitch identification, receive slow inhibitory inputs. In contrast, T-stellate cells, which encode slower envelope information, receive inhibition that is eightfold faster. Both types of inhibition improved the precision of spike timing but engage different cellular mechanisms and operate on different timescales. Computer models reveal that slow IPSCs in bushy cells can improve spike timing on the scale of tens of microseconds. Although fast and slow IPSCs in T-stellate cells improve spike timing on the scale of milliseconds, only fast IPSCs can enhance the detection of narrowband acoustic signals in a complex background. Our results suggest that target-specific IPSC kinetics are critical for the segregated parallel processing of temporal information from the sensory environment.
声环境包含了从微秒到数十秒时间尺度上的生物相关信息。听觉脑干核通过起源于耳蜗核的不同细胞类型的并行通路来处理这些时间信息。尽管离子通道和兴奋性突触在时间处理中的作用已经得到了很好的研究，但抑制作用的贡献还不太清楚。在这里，我们在 CBA/CaJ 小鼠中表明，耳蜗腹核的两个主要投射神经元，即布什细胞和 T 形细胞，接收具有不同突触电导时程的甘氨酸能抑制作用。布什细胞提供用于声音定位和音高识别的精确定时尖峰序列，接收缓慢的抑制性输入。相比之下，编码较慢包络信息的 T 形细胞接收的抑制作用快 8 倍。这两种类型的抑制作用都提高了尖峰定时的精度，但涉及不同的细胞机制，并在不同的时间尺度上起作用。计算机模型表明，布什细胞中的慢 IPSC 可以提高数十微秒时间尺度上的尖峰定时精度。尽管 T 形细胞中的快和慢 IPSC 可以提高毫秒时间尺度上的尖峰定时精度，但只有快 IPSC 可以增强复杂背景下窄带声信号的检测。我们的结果表明，针对特定目标的 IPSC 动力学对于从感觉环境中分离并行处理时间信息至关重要。
