The nucleus preeminentialis (PE) is a large central structure that projects both directly and indirectly to the electrosensory lobe (ELL) where the primary afferents from electroreceptors terminate. PE receives electrosensory input directly from ELL and also from higher stages of the electrosensory pathway. PE is thus an important part of a central feedback loop that returns electrosensory information from higher stages of the system to the initial stage in ELL. 2. This study describes the field potentials and single-unit activity that are evoked in PE by electrosensory stimuli and by corollary discharge signals associated with the motor command that drives the electric organ to discharge. All recordings were extracellular in this study. 3. Two types of negative-going corollary discharge-evoked field potentials were found in PE: 1) a shallow, long-lasting negative wave with a latency at the peak of approximately 11 ms, and 2) a more sharply falling and larger negative wave with a shorter latency at the peak of approximately 9 ms. The long-latency wave was predominant in the dorsolateral and posterior parts of PE, whereas the short-latency wave was predominant in the medial and rostral regions. Both waves were only found in PE and thus can serve for its identification. 4. Electrosensory stimuli given either locally to a restricted skin region or symmetrically to the entire body evoked characteristic field potentials in both regions of PE. The mean latency between the stimulus and the peak of the response was 6.9 ms in the early negativity region and 12.2 ms in the late negative region. The responses to such stimuli were strongly facilitated by the electric organ corollary discharge. 5. Field potential responses to the electric organ corollary discharge were markedly plastic. Responses to the corollary discharge plus a paired electrosensory stimulus decreased over time and the response to the corollary discharge alone was markedly enhanced after a period of such pairing. 6. Local electrosensory stimulation of the skin showed that the caudal-rostral body axis is mapped from dorsal-medial to ventral-lateral in PE. The same somatotopy was found in the regions of the early and late negatives. The ventral and dorsal body appeared not to be separately mapped in PE. The areas representing the head and chin appendage ("Schnauzenorgan") are especially large in PE, due presumably to the high density of electroreceptors in these areas. 7. Two main types of units were recorded in PE: 1) inhibitory (I) cells with a corollary discharge response that was inhibited by an electrosensory stimulus to the center of their receptive fields; and 2) excitatory (E) cells with an excitatory response to electrosensory stimuli that was facilitated by the corollary discharge. Some of the E cells responded to the corollary discharge alone and some did not. Most cells appeared to be responding to input from mormyromast electroreceptors, but a few cells were driven by ampullary electroreceptors and a few by Knollenorgan electroreceptors. 8. The corollary discharge effects on I cells and E cells were plastic and depended on previous pairing with a sensory stimulus. The corollary discharge facilitation of E cells and inhibition of I cells decreased during pairing with a sensory stimulus, and the corollary discharge-driven excitation of I cells was much larger after pairing than before. 9. The results provide an initial overview of a major component in the control of electrosensory information processing by recurrent feedback from higher stages of the system.
摘要
优势核（PE）是一个大型中央结构，它直接和间接地投射到电感觉叶（ELL），电感受器的初级传入纤维在此终止。PE 直接从 ELL 以及电感觉通路的更高阶段接收电感觉输入。因此，PE 是中央反馈回路的重要组成部分，该回路将电感觉信息从系统的更高阶段返回至 ELL 的初始阶段。2. 本研究描述了电感觉刺激以及与驱动电器官放电的运动指令相关的伴随放电信号在 PE 中诱发的场电位和单单位活动。本研究中的所有记录均为细胞外记录。3. 在 PE 中发现了两种类型的负向伴随放电诱发场电位：1）一种浅的、持续时间长的负波，其峰值潜伏期约为 11 毫秒；2）一种下降更陡峭、幅度更大的负波，其峰值潜伏期较短，约为 9 毫秒。长潜伏期波在 PE 的背外侧和后部占主导，而短潜伏期波在内侧和吻侧区域占主导。这两种波仅在 PE 中发现，因此可用于其识别。4. 局部施加于受限皮肤区域或对称施加于全身的电感觉刺激在 PE 的两个区域均诱发了特征性场电位。在早期负性区域，刺激与反应峰值之间的平均潜伏期为 6.9 毫秒，在晚期负性区域为 12.2 毫秒。电器官伴随放电强烈促进了对这种刺激的反应。5. 对电器官伴随放电的场电位反应具有明显的可塑性。对伴随放电加配对电感觉刺激的反应随时间减少，而在经过一段时间的这种配对后，对单独伴随放电的反应明显增强。6. 对皮肤的局部电感觉刺激表明，在 PE 中，尾 - 吻身体轴从背 - 内侧映射到腹 - 外侧。在早期和晚期负性区域发现了相同的躯体定位。腹侧和背侧身体在 PE 中似乎没有分别映射。代表头部和下巴附属器（“口鼻器官”）的区域在 PE 中特别大，推测是由于这些区域电感受器的高密度。7. 在 PE 中记录到两种主要类型的神经元：1）抑制性（I）细胞，其伴随放电反应受到对其感受野中心的电感觉刺激的抑制；2）兴奋性（E）细胞，其对电感觉刺激的兴奋性反应受到伴随放电的促进。一些 E 细胞仅对伴随放电有反应，而一些则没有。大多数细胞似乎对电丘电感受器的输入有反应，但少数细胞由壶腹电感受器驱动，还有少数由球囊器官电感受器驱动。8. 伴随放电对 I 细胞和 E 细胞的影响具有可塑性，并且取决于先前与感觉刺激的配对。在与感觉刺激配对期间，E 细胞的伴随放电促进和 I 细胞的抑制减少，并且配对后 I 细胞的伴随放电驱动兴奋比之前大得多。9. 这些结果提供了关于系统更高阶段的递归反馈对电感觉信息处理控制中的一个主要成分的初步概述。
