Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 113-0033 Tokyo, Japan.
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 113-0033 Tokyo, Japan
Proc Natl Acad Sci U S A. 2019 Sep 10;116(37):18673-18683. doi: 10.1073/pnas.1821716116. Epub 2019 Aug 27.
Animals demonstrate flexible behaviors through associative learning based on their experiences. Deciphering the neural mechanisms for sensing and integrating multiple types of sensory information is critical for understanding such behavioral controls. The soil nematode avoids salt concentrations it has previously experienced under starvation conditions. Here, we identify a pair of sensory neurons, the ASG neuron pair, which in cooperation with the ASER salt-sensing neuron generate starvation-dependent salt avoidance. Animals whose sensory input is restricted to only ASER failed to show learned avoidance due to inappropriately directed navigation behaviors. However, their navigation through a salt concentration gradient was improved by allowing sensory inputs to ASG in addition to ASER. Detailed behavioral analyses of these animals revealed that input from ASG neurons is required not only for controlling the frequency of initiating a set of sharp turns (called pirouettes) based on detected ambient salt concentrations but also adjusting the migration direction during pirouettes. Optogenetic activation of ASER by ChR2 induced turning behaviors in a salt concentration-dependent manner where presence of intact ASG was important for the starvation-dependent responses. Calcium imaging of the activity of ASG neurons in freely moving worms revealed that ASG is activated upon turning behavior. Our results indicate that ASG neurons cooperate with the ASER neuron to generate destination-directed reorientation in starvation-associated salt concentration avoidance.
动物通过基于经验的联想学习表现出灵活的行为。破译感知和整合多种类型感觉信息的神经机制对于理解这种行为控制至关重要。土壤线虫在饥饿条件下避免以前经历过的盐浓度。在这里，我们鉴定了一对感觉神经元，即 ASG 神经元对，它与 ASER 盐感觉神经元合作产生饥饿依赖性的盐回避。其感觉输入仅限于 ASER 的动物由于导航行为不当而无法表现出习得的回避。然而，通过允许除 ASER 之外的 ASG 进行感觉输入，它们在盐浓度梯度中的导航得到了改善。对这些动物进行的详细行为分析表明，ASG 神经元的输入不仅对于控制基于检测到的环境盐浓度的一组急转弯（称为旋转）的起始频率是必需的，而且对于在旋转期间调整迁移方向也是必需的。ChR2 对 ASER 的光遗传学激活以盐浓度依赖的方式诱导转弯行为，其中完整的 ASG 的存在对于饥饿依赖性反应很重要。在自由移动的蠕虫中对 ASG 神经元活性进行钙成像表明，ASG 在转弯行为时被激活。我们的结果表明，ASG 神经元与 ASER 神经元合作，在与饥饿相关的盐浓度回避中产生定向重新定向。
