Dynamics of electric sensing

生物电场在自然界中无处不在；它们是我们动作、心跳和思想的基础。在大脑中，这些电场来自控制行为的神经元网络的时变活动，并反映在脑电图（EEG）中，我们可以通过放置在头皮上的感应电极记录脑电图。虽然脑电图可以告诉我们大脑的整体状态，但我们对如何从这个全局信号中确定局部网络的功能知之甚少。想象一下，听到远处体育场里的人群不断发出吼声，你知道有什么事情发生了，但你不知道是什么，也不知道为什么，也不知道体育场里是谁在欢呼。我们想知道像脑电图这样的信号背后的“是什么”、“为什么”和“谁”。事实证明，大自然已经解决了一个类似的问题：电鱼利用电场的时空变化来描述它们的环境。

Bioelectric fields are ubiquitous in nature; they underlie our movements, our heart beat, and our thoughts. In the brain, these electric fields arise from the time-varying activity of the neuronal networks that control behaviour, and are reflected in the electroencephalogram (EEG) that we can record with sensing electrodes placed on our scalp. While the EEG can tell us about overall brain state, we know relatively little about how to determine the function of local networks from this global signal. Imagine hearing the repeated roars of a crowd in a distant stadium you know something is happening, but you don't know what or why, or who in the stadium is actually cheering. We would like to know the “what”, “why” and “who” underlying signals like the EEG. It turns out that nature has already solved a similar problem: electric fish use the spatiotemporal changes in electric fields to characterize their environment. Weakly electric fish generate an oscillating electric field that is perturbed by surrounding objects. These perturbations are encoded by specialized electroreceptors on the skin, allowing the fish to navigate, capture prey and communicate in the dark. This involves a significant challenge: electric field perturbations are miniscule (entirely undetectable to us) and often contaminated with high levels of background noise, including the electric signals of other fish. The fish overcomes this challenge using two strategies. First, electric fish dynamically swim backwards and forwards, using motion to extract maximal information. Second, the clock-like timing of their oscillating electric field is much more precise than any other biological clock, allowing even the smallest modulations to be detected. My proposal focuses on these strategies in the context of two fundamental questions: (1) How does motion influence the acquisition of sensory information? (2) How do brain networks control timing precision? Our approach is multi-disciplinary, combining behavioural studies with electrophysiology and computational modeling. We use a virtual reality system to probe electrosensory perception while controlling the information available to the fish through active movements. And using single neuron recordings and specific network manipulations, we discover the brain mechanisms that enable highly precise neural activity. These studies are informed by detailed computational models of electric field dynamics and neural networks. This multidisciplinary training ground is ideal for students at all levels, preparing them for a wide range of careers in biotechnology and high-technology, as well as in government labs and academia. Understanding this exquisite electric sense will not only provide a window into the exotic world of electric fish, but will also increase our understanding of sensing in general. In turn, this will impact diverse areas in neuroscience and enable us to better-interpret the electric fields in our own brains.