Bastian J
J Neurosci. 1986 Feb;6(2):553-62. doi: 10.1523/JNEUROSCI.06-02-00553.1986.
The electrosensory lateral line lobe (ELLL) of weakly electric fish, the primary electrosensory processing station, receives a large descending input from the midbrain in addition to the input from the electroreceptor afferents. The role of a major component of this descending input in determining the properties of ELLL output neurons was investigated. The descending input was reduced or eliminated by microinjections of the local anesthetic lidocaine or by small lesions. This treatment increased the responses of the ELLL output neurons to suprathreshold stimuli by about 300% and also increased the size of the neurons' receptive fields for moving electrolocation targets and the resolution with which they encode target distance. The neurons' threshold sensitivity and tuning to amplitude modulation frequency were unchanged by removal of the descending input. The results of this study show that this portion of the descending input to the ELLL normally mediates an inhibition that controls the responsiveness of ELLL output neurons. This descending input could function as a gain control mechanism, allowing the animal to modulate the sensitivity of the electrosensory system in response to changing environmental conditions.
弱电鱼的电感觉侧线叶（ELLL）作为主要的电感觉处理中枢，除了接收来自电感受器传入纤维的输入外，还从中脑接收大量下行输入。研究了这种下行输入的一个主要成分在决定ELLL输出神经元特性方面的作用。通过微量注射局部麻醉剂利多卡因或进行小损伤，减少或消除下行输入。这种处理使ELLL输出神经元对阈上刺激的反应增加了约300%，同时也增加了神经元对移动电定位目标的感受野大小以及它们编码目标距离的分辨率。去除下行输入后，神经元的阈值敏感性和对调幅频率的调谐没有变化。这项研究结果表明，ELLL的这部分下行输入通常介导一种抑制作用，控制ELLL输出神经元的反应性。这种下行输入可以作为一种增益控制机制，使动物能够根据环境条件的变化调节电感觉系统的敏感性。
