Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel ; Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel.
PLoS One. 2013 Nov 27;8(11):e79831. doi: 10.1371/journal.pone.0079831. eCollection 2013.
Rats repeatedly sweep their facial whiskers back and forth in order to explore their environment. Such explorative whisking appears to be driven by central pattern generators (CPGs) that operate independently of direct sensory feedback. Nevertheless, whisking can be modulated by sensory feedback, and it has been hypothesized that some of this modulation already occurs within the brainstem. However, the interaction between sensory feedback and CPG activity is poorly understood. Using the visual language of statecharts, a dynamic, bottom-up computerized model of the brainstem loop of the whisking system was built in order to investigate the interaction between sensory feedback and CPG activity during whisking behavior. As a benchmark, we used a previously quantified closed-loop phenomenon of the whisking system, touched-induced pump (TIP), which is thought to be mediated by the brainstem loop. First, we showed that TIPs depend on sensory feedback, by comparing TIP occurrence in intact rats with that in rats whose sensory nerve was experimentally cut. We then inspected several possible feedback mechanisms of TIPs using our model. The model ruled out all hypothesized mechanisms but one, which adequately simulated the corresponding motion observed in the rat. Results of the simulations suggest that TIPs are generated via sensory feedback that activates extrinsic retractor muscles in the mystacial pad. The model further predicted that in addition to the touching whisker, all whiskers found on the same side of the snout should exhibit a TIP. We present experimental results that confirm the predicted movements in behaving rats, establishing the validity of the hypothesized interaction between sensory feedback and CPG activity we suggest here for the generation of TIPs in the whisking system.
老鼠会反复地来回扫动它们的面部触须，以探索周围的环境。这种探索性的触须运动似乎是由独立于直接感觉反馈的中枢模式发生器（CPG）驱动的。然而，触须运动可以通过感觉反馈进行调节，并且有人假设这种调节中的一部分已经发生在脑干中。然而，感觉反馈和 CPG 活动之间的相互作用还了解甚少。使用状态图的可视化语言，构建了一个关于触须系统脑干回路的动态、自下而上的计算机模型，以研究在触须运动行为中感觉反馈和 CPG 活动之间的相互作用。作为基准，我们使用了以前量化的触须系统闭环现象——触摸诱导泵（TIP），它被认为是由脑干回路介导的。首先，我们通过比较实验切断感觉神经的大鼠和完整大鼠的 TIP 发生情况，证明了 TIP 依赖于感觉反馈。然后，我们使用模型检查了 TIP 的几种可能的反馈机制。该模型排除了所有假设的机制，但有一种机制除外，该机制充分模拟了在大鼠中观察到的相应运动。模拟结果表明，TIP 是通过感觉反馈产生的，这种反馈激活了面部触须垫中的外展肌。该模型进一步预测，除了被触摸的触须外，位于口鼻部同一侧的所有触须都应该表现出 TIP。我们提出了实验结果，证实了行为大鼠中预测的运动，为我们在这里提出的关于感觉反馈和 CPG 活动之间的相互作用生成 TIP 的假设提供了有效性。
