Active sensing becomes rhythmic during oscillatory behaviour in electric fish

Rather than wait passively for signals to be detected by their sensors, animals actively move in order to gather information from their environment. Furthermore, when sensing is performed by means of rhythmic movements, reafferent sensory streams are also rhythmic, which is advantageous for sensory processing. Here, we report on and characterize an hitherto unknown behavioural state of pulse-type weakly electric fish during which electrosensory acquisition becomes rhythmic and is coupled to low-frequency movement. The oscillatory nature of this sensory sampling strategy is in stark contrast to that exhibited during other behaviours.

To characterize the oscillatory dynamics of these rhythmic behavioural states, we identify and extract them from long-term observations of freely-moving fish. By applying t-distributed Stochastic Neighbor Embedding on the wavelet spectra of the inter-pulse interval time series, we achieve a successfully classification of behavioural states. Two dominant frequency bands appear during oscillatory behaviour: around 0.5 and 1 Hz. By analyzing the associated bandpass filtered signals, we find that they exhibit hallmark features of synchronization, including phase slips and limit cycles of the phase dynamics on the torus.