Computational Neuroscience, Department for Neuroscience, University of Oldenburg, Oldenburg, Germany.
Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA.
Sci Rep. 2018 Feb 14;8(1):3046. doi: 10.1038/s41598-018-21272-6.
Touch triggers highly precise behavioural responses in the leech. The underlying network of this so-called local bend reflex consists of three layers of individually characterised neurons. While the population of mechanosensory cells provide multiplexed information about the stimulus, not much is known about how interneurons process this information. Here, we analyse the responses of two local bend interneurons (cell 157 and 159) to a mechanical stimulation of the skin and show their response characteristics to naturalistic stimuli. Intracellular dye-fills combined with structural imaging revealed that these interneurons are synaptically coupled to all three types of mechanosensory cells (T, P, and N cells). Since tactile stimulation of the skin evokes spikes in one to two cells of each of the latter types, interneurons combine inputs from up to six mechanosensory cells. We find that properties of touch location and intensity can be estimated reliably and accurately based on the graded interneuron responses. Connections to several mechanosensory cell types and specific response characteristics of the interneuron types indicate specialised filter and integration properties within this small neuronal network, thus providing evidence for more complex signal processing than previously thought.
触碰会引发水蛭产生高度精确的行为反应。这种所谓的局部弯曲反射的基础网络由三层具有各自特征的神经元组成。虽然机械感受器细胞群提供了关于刺激的多路复用信息，但对于中间神经元如何处理这些信息知之甚少。在这里，我们分析了两个局部弯曲中间神经元（细胞 157 和 159）对皮肤机械刺激的反应，并展示了它们对自然刺激的反应特征。细胞内染色结合结构成像表明，这些中间神经元与所有三种机械感受器细胞（T、P 和 N 细胞）都存在突触连接。由于皮肤的触觉刺激会在后面提到的每一种类型的细胞中引发一个到两个细胞的尖峰，因此中间神经元将来自多达六个机械感受器细胞的输入进行组合。我们发现，基于分级中间神经元的反应，可以可靠且准确地估计触摸位置和强度。与几种机械感受器细胞类型的连接以及中间神经元类型的特定反应特征表明，在这个小的神经网络中存在专门的滤波器和集成特性，从而为比以前认为的更复杂的信号处理提供了证据。
