Van Susteren Grace E, Mogdans Joachim
Department of Biology, University of Washington, Seattle, WA, USA.
Institute for Zoology, University of Bonn, Bonn, Germany.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2025 Jan;211(1):69-85. doi: 10.1007/s00359-024-01715-4. Epub 2024 Sep 17.
With the mechanosensory lateral line system, fish and semi-aquatic amphibians detect water movements and pressure gradients. Hydrodynamic information picked up by the lateral line receptors is relayed via peripheral nerves to the lateral line brainstem and from there to the midbrain torus semicircularis. Most prior electrophysiological studies of the lateral line were done under still-water conditions, even though natural environments encountered by fish include bulk-flow. Flow velocity and direction sensing are likely important to fish as they navigate variable, turbulent environments, but to date, only few studies have gathered information on the processing of bulk water flow by midbrain units. Here, we recorded from lateral line units in the torus semicircularis while presenting various bulk flow velocities in anterior-to-posterior and posterior-to-anterior flow directions. We studied (1) the temporal spike patterns of mechanosensory midbrain units, (2) the processing of bulk water flow velocity by these units, and (3) the processing of bulk water flow direction. We found that midbrain mechanosensory units alter their discharge rate during bulk water flow - some units responded to flow by increasing their discharge rate but did not vary this rate significantly with flow velocity, while others exhibited increasing discharge rates with increasing flow velocity. Units directly coding for flow direction were not found.
借助机械感觉侧线系统，鱼类和半水生两栖动物能够检测水的运动和压力梯度。侧线感受器收集到的流体动力学信息通过外周神经传递到侧线脑干，再从那里传递到中脑半规管隆起。尽管鱼类所处的自然环境包括大量水流，但此前大多数关于侧线的电生理研究都是在静水条件下进行的。流速和方向感知对于鱼类在多变、湍流的环境中导航可能很重要，但迄今为止，只有少数研究收集了关于中脑神经元处理大量水流的信息。在这里，我们在中脑半规管隆起的侧线神经元上进行记录，同时呈现从前到后和从后到前的不同水流速度。我们研究了：（1）机械感觉中脑神经元的时间发放模式；（2）这些神经元对大量水流速度的处理；（3）大量水流方向的处理。我们发现，在大量水流期间，中脑机械感觉神经元会改变它们的发放率——一些神经元通过增加发放率对水流做出反应，但发放率不会随流速显著变化，而另一些神经元则随着流速增加而表现出发放率增加。未发现直接编码水流方向的神经元。
