Dynamics of electric sensing: neurobiology, physics & behaviour

We are studying electric sensing in weakly electric fish. These fish inhabit dark and murky waters and in general do not rely on visual cues, so the electric sense plays a key role in prey capture, exploration, and communication. These fish generate an oscillating high-frequency (~1000Hz) electric field with clock-like timing precision. Objects in the environment perturb this electric field; these perturbations are sensed using specialized electroreceptors distributed on the entire body surface of the fish.

Electric fish must overcome significant challenges to sense with electric fields. One is that the perturbations produced by objects are not only very small, but are contaminated by many sources of noise (imagine trying to hear a whisper amongst a cheering crowd). Another challenge is that these fish must use a 2-dimensional sensory signal (from their skin-surface electroreceptors) to infer the goings-on in their 3-dimensional world. Despite such challenges, these fish can reliably capture very small prey and effectively interact with conspecifics. But what does an electrosensory world "look like"? What information is actually available in the electric field perturbations? How do these fish perform such exquisite behaviors in dynamic and noisy environments? And further, how do they deal with the high energetic costs of generating high-frequency electric fields?

We're beginning to tackle these problems using a variety of approaches. In general, our research projects focus on two aspects of electric sensing:

1. The physics of the electric field and dynamic electrosensory stimuli. We are using computational tools, including finite-element methods, to study the physical basis of the electric field and gain insight into natural electrosensory stimuli and the information contained in field perturbations (see our software: fish2eod). These modeling studies lead to hypotheses that we can test using quantitative behavioural studies to better understand perceptual limits and the salient features of electrosensory stimuli.

2. The neural dynamics underlying electric field generation. We are using electrophysiology and computational modeling to study the biophysical mechanisms and energetic costs underlying the control of the electric organ discharge (EOD). The EOD has clock-like precision and is one of the most precise of all biological oscillators, yet it is behaviourally modulated on millisecond timescales for electrocommunication. How is this balance between precision and flexibility achieved?

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