Neuroanatomical properties of 'time comparison circuit' in weakly electric fishes

弱电鱼对来自身体不同部位的电感觉信号的微秒时间差表现出行为敏感性。假设的时间比较电路由两种时间编码神经元和一个小细胞组成，这两种时间编码神经元收敛到一个小细胞中。在这里，我研究了两个物种的时间编码回路中的突触传递类型。免疫组织化学研究发现，时间编码神经元的一个输入是抑制性的。然而，在裸子形brachyhypoomus（裸子形）中，常规电子显微镜显示两个输入都是兴奋的。这种比较分析揭示了时间编码神经元的拓扑结构是相同的，在所有主要群体的其他弱电鱼迄今为止研究。然而，突触传递到小细胞（一个时间比较器）的模式在物种之间是不同的。

Weakly electric fish shows behavioral sensitivity to microsecond time difference between electrosensory signals from different body areas. The hypothetical time comparison circuit consists oftwo types of time-coding neurons and a small cell, to which the two time-coding neurons converged. Here I studied the type of synaptic transmission in the time-coding circuit in two species. I immunohistochemically found that one of the inputs of the time-coding neuron is inhibitory in Gymnarchus (mormyriform). However, in Brachyhypopomus (gymnotiform), conventional electron microscopy showed that both inputs are excitatory. This comparative analysis revealed that the topologies of time coding neurons are identical in all major groups of other weakly electric fishes so far studied. However, the modes of synaptic transmission to the small cell, a time comparator, are different between species.