Deptartment of Microbiology and Immunology, Montana State University, Bozeman, Montana.
J Neurophysiol. 2022 Apr 1;127(4):1185-1197. doi: 10.1152/jn.00042.2022. Epub 2022 Mar 30.
The cercal sensory system of cricket mediates the detection, localization, and identification of air current signals generated by predators, mates, and competitors. This mechanosensory system has been used extensively for experimental and theoretical studies of sensory coding at the cellular and system levels. It is currently thought that sensory interneurons (INs) in the terminal abdominal ganglion extract information about the direction, velocity, and acceleration of the air currents in the animal's immediate environment and project a coarse-coded representation of those parameters to higher centers. All feature detection is thought to be carried out in higher ganglia by more complex, specialized circuits. We present results that force a substantial revision of current hypotheses. Using multiple extracellular recordings and a special sensory stimulation device, we demonstrate that four well-studied interneurons in this system respond with high sensitivity and selectivity to complex dynamic multidirectional features of air currents that have a spatial scale smaller than the physical dimensions of the cerci. The INs showed much greater sensitivity for these features than for unidirectional bulk-flow stimuli used in previous studies. Thus, in addition to participating in the ensemble encoding of bulk airflow stimulus characteristics, these interneurons are capable of operating as feature detectors for naturalistic stimuli. In this sense, these interneurons are encoding and transmitting information about different aspects of their stimulus environment; they are multiplexing information. Major aspects of the stimulus-response specificity of these interneurons can be understood from the dendritic anatomy and connectivity with the sensory afferent map. A set of sensory interneurons that have been studied for over 30 years by several different research groups were discovered to have previously unknown encoding characteristics. As well as encoding the direction of bulk airflow with a coarse-coding scheme as shown in previous studies, these interneurons are also responsive to very small-scale, directionally complex air current waveforms. This feature sensitivity can be understood in terms of the cells' complex dendritic branching patterns.
蟋蟀的尾感器系统介导了对气流信号的检测、定位和识别，这些气流信号由捕食者、配偶和竞争者产生。这个机械感觉系统已被广泛用于细胞和系统水平的感觉编码的实验和理论研究。目前认为，终末腹神经节中的感觉神经元（INs）提取关于动物周围环境中气流的方向、速度和加速度的信息，并向更高的中枢投射这些参数的粗编码表示。目前认为，所有的特征检测都是由更复杂、专门的电路在更高的神经节中完成的。我们的研究结果迫使对当前假设进行重大修正。使用多个细胞外记录和特殊的感觉刺激设备，我们证明了这个系统中的四个研究充分的中间神经元对气流的复杂动态多方向特征具有高度的敏感性和选择性，这些特征的空间尺度小于尾须的物理尺寸。与以前研究中使用的单向整体流刺激相比，这些中间神经元对这些特征的敏感性要高得多。因此，除了参与整体气流刺激特征的编码之外，这些中间神经元还能够作为自然刺激的特征检测器。从这个意义上说，这些中间神经元正在对其刺激环境的不同方面进行编码和传输信息；它们正在进行信息的复用。这些中间神经元的刺激-反应特异性的主要方面可以从树突解剖结构和与感觉传入图的连接中得到理解。一组已经被几个不同的研究小组研究了 30 多年的感觉神经元被发现具有以前未知的编码特征。除了以前的研究表明的对整体气流方向的粗编码方案进行编码外，这些中间神经元还对非常小尺度、方向复杂的气流波形有反应。这种特征敏感性可以根据细胞复杂的树突分支模式来理解。
