Ritzmann R E, Pollack A J
Department of Biology, Case Western Reserve University, Cleveland, Ohio 44106.
J Neurobiol. 1994 Sep;25(9):1113-28. doi: 10.1002/neu.480250907.
Recent findings indicate that cockroaches escape in response to tactile stimulation as well as they do in response to the classic wind puff stimulus. The thoracic interneurons that receive inputs from ventral giant interneurons also respond to tactile stimulation and, therefore, represent a potential site of convergence between wind and tactile stimulation, as well as other sensory modalities. In this article, we characterize the tactile response of these interneurons, which are referred to as type-A thoracic interneurons (TIAs). In response to tactile stimulation of the body cuticle, TIAs typically respond with a short latency biphasic depolarization which often passes threshold for action potentials. The biphasic response is not typical of responses to wind stimulation nor of tactile stimulation of the antennae. It is also not seen in tactile responses of thoracic interneurons that are not part of the TIA group. The responses of individual TIAs to stimulation of various body locations were mapped. The left-right directional properties of TIAs are consistent with their responses to wind puffs from various different directions. Cells that respond equally well to wind from the left and right side also respond equally well to tactile stimuli on the left and right side of the animal's body. In contrast, cells that are biased to wind on one side are also biased to tactile stimulation on the same side. In general, tactile responses directed at body cuticle are phasic rather than tonic, occurring both when the tactile stimulator is depressed and released. The response reflects stimulus strength and follows repeated stimulation quite well. However, the first phase of the biphasic response is more robust during high-frequency stimulation than the second phase. TIAs also respond to antennal stimulation. However, here the response characteristics are complicated by the fact that movement of either antenna evokes descending activity in both left and right thoracic connectives. The data suggest that the TIAs make up a multimodal site of sensory convergence that is capable of generating an oriented escape turn in response to any one of several sensory cues.
最近的研究结果表明，蟑螂对触觉刺激的逃避反应与对经典风刺激的反应一样好。从腹侧巨中间神经元接收输入的胸中间神经元也对触觉刺激有反应，因此，它代表了风刺激和触觉刺激以及其他感觉模态之间潜在的汇聚位点。在本文中，我们描述了这些中间神经元的触觉反应，它们被称为A型胸中间神经元（TIA）。对身体表皮进行触觉刺激时，TIA通常会以短潜伏期双相去极化做出反应，这种去极化常常达到动作电位的阈值。这种双相反应既不是对风刺激的典型反应，也不是对触角触觉刺激的典型反应。在不属于TIA组的胸中间神经元的触觉反应中也看不到这种反应。绘制了单个TIA对身体不同部位刺激的反应图。TIA的左右方向特性与其对来自不同方向的风刺激的反应一致。对来自左侧和右侧的风反应同样良好的细胞，对动物身体左侧和右侧的触觉刺激反应也同样良好。相反，偏向一侧风刺激的细胞也偏向同一侧的触觉刺激。一般来说，针对身体表皮的触觉反应是相位性的而非紧张性的，在触觉刺激器按下和松开时都会出现。该反应反映刺激强度，并且对重复刺激的跟随性很好。然而，在高频刺激期间，双相反应的第一相比第二相更强烈。TIA也对触角刺激有反应。然而，这里的反应特性因任一触角的运动都会在左右胸神经连索中引发下行活动这一事实而变得复杂。数据表明，TIA构成了一个多模态感觉汇聚位点，能够响应几种感觉线索中的任何一种产生定向逃避转向。
