Nonlinearities facilitate the encoding of a wide range of beat frequencies and amplitudes in primary electrosensory afferents

Abstract

In this work, the influence of nonlinearities on stimulus encoding in the primary sensory afferents of weakly electric fish of the species Apteronotus leptorhynchus was investigated. These fish produce an electric organ discharge (EOD) with a fish-specific frequency. When the EOD of one fish interferes with the EOD of another fish, it results in a signal with a periodic amplitude modulation, called beat. The beat provides information about the sex and size of the encountered conspecific and is the basis for communication. The beat frequency is predicted as the difference between the EOD frequencies and the beat amplitude corresponds to the size of the smaller EOD field. Primary sensory afferents, the P-units, phase-lock to the EOD and encode beats with changes in their firing rate. In this work, the influence of nonlinearities on the encoding of beat parameters such as frequency and amplitude was investigated. It was demonstrated that a smooth threshold nonlinearity at the synapse between electroreceptors and P-unit afferents enables the representation of high beat frequencies in a two-fish scenario, thus providing the basis for potential interspecies communication. Second-order susceptibility in the spiking response of regular firing P-units, was demonstrated to contribute to the detection of faint signals in a three-fish setting, the so-called "electrosensory cocktail party". Bursting was identified to increase this nonlinearity. Two-beat suppression and the reduced representation of the receiver EOD in the firing rate of P-units were found to contribute to the encoding of a wide range of beat amplitudes on a single-cell level.

Die Dissertation ist gesperrt bis zum 12. April 2026 !