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

弱电鱼类对来自不同身体区域的电感信号之间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个时间编码神经元和一个小细胞组成，两个时间编码神经元汇聚到一个小细胞上。在这里，我研究了两个物种的时间编码电路中突触传递的类型。我用免疫组织化学方法发现，时间编码神经元的其中一个输入信号在脊束核(Mormyriform)是抑制性的。然而，在短臂形目动物中，常规的电子显微镜显示两种输入都是兴奋性的。这种比较分析表明，到目前为止所研究的所有主要弱电鱼类的时间编码神经元的拓扑结构都是相同的。然而，突触传递到时间比较器小细胞的方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.