Guo Y X, Kawasaki M
Department of Biology, University of Virginia, Charlottesville, Virginia 22903, USA.
J Neurosci. 1997 Mar 1;17(5):1761-8. doi: 10.1523/JNEUROSCI.17-05-01761.1997.
Differential-phase-sensitive neurons in the electrosensory lateral line lobe (ELL) of the African electric fish, Gymnarchus niloticus, are sensitive to time disparities on the order of microseconds between afferent action potentials. These action potentials fire in a phase-locked manner in response to the animal's own wave-type electric organ discharges (EODs) (). The time disparity is one of the essential cues for an electrical behavior, the jamming avoidance response (JAR). To gain an insight into the accurate temporal processing in the ELL, firing time accuracy and dynamic response properties of action potentials of the phase-locked neurons (PLNs) in the ELL were examined. The temporal accuracy of the entire neuronal circuit for the JAR was also measured using behavioral responses. Standard deviation of firing times of PLNs' action potentials was approximately 6 micro;sec. The PLNs represent zerocrossing times of each stimulus cycle with this accuracy even when stimulus phase was modulated at high frequencies ( approximately 50 Hz). Distinct JAR occurred when time disparity was diminished below 1 micro;sec, and a marginal JAR could still be detected with a time disparity of 100 nsec. Standard deviation of the firing times of EODs was approximately several hundred nanoseconds. This stability of the EOD, however, was demonstrated to be unnecessary for the JAR. JARs occurred even when a large artificial jitter ( approximately 60 micro;sec) was introduced to a stimulus that mimicked fish's own EOD and the time disparity for JAR was diminished to 1 micro;sec. This immunity of JAR to the EOD jitter is explained by the insensitivity of the differential-phase-sensitive neurons in the ELL to a common phase modulation. The JAR of the South American electric fish, Eigenmannia, also occurs in response to stimuli that generate comparably small phase differences (; ). The present study revealed that the independently evolved Eigenmannia and Gymnarchus exhibit a comparative level of remarkable temporal accuracy.
非洲电鱼裸臀鱼电感觉侧线叶（ELL）中的微分相位敏感神经元，对传入动作电位之间微秒级的时间差异敏感。这些动作电位以锁相方式发放，以响应动物自身的波型电器官放电（EODs）（）。时间差异是电行为——避扰反应（JAR）的重要线索之一。为深入了解ELL中的精确时间处理，研究了ELL中锁相神经元（PLNs）动作电位的发放时间准确性和动态响应特性。还利用行为反应测量了JAR整个神经回路的时间准确性。PLNs动作电位发放时间的标准差约为6微秒。即使在高频（约50赫兹）调制刺激相位时，PLNs仍能以这种精度表征每个刺激周期的过零时间。当时间差异减小到1微秒以下时，会出现明显的JAR，时间差异为100纳秒时仍能检测到边缘JAR。EODs发放时间的标准差约为几百纳秒。然而，已证明EOD的这种稳定性对JAR并非必要。即使在模拟鱼自身EOD的刺激中引入大的人工抖动（约60微秒），且JAR的时间差异减小到1微秒时，仍会出现JAR。ELL中微分相位敏感神经元对共同相位调制不敏感，解释了JAR对EOD抖动的这种抗性。南美电鱼艾氏电鳗的JAR也会在对产生相对小相位差（；）的刺激做出反应时出现。本研究表明，独立进化的艾氏电鳗和裸臀鱼表现出相当水平的显著时间准确性。
