Tethered unitary recordings suggest a spike-timing electrosensory code in the electrosensory lobe of Gymnotus omarorum

Ana-Carolina Pereira,Ángel A Caputi,Pedro A Aguilera,Alejo Rodríguez-Cattáneo,Ayca Ergul

doi:10.1017/exp.2020.20

Abstract

AbstractEvaluation of neural activity during natural behaviours is essential for understanding how the brain works. Here we show that neuron-specific self-evoked firing patterns are modulated by an object’s presence, at the electrosensory lobe neurons of tethered-moving Gymnotus omarorum. This novel preparation shows that electrosensory signals in these pulse-type weakly electric fish are not only encoded in the number of spikes per electric organ discharge (EOD), as is the case in wave-type electric fish, but also in the spike timing pattern after each EOD, as found in pulse-type Mormyroidea. Present data suggest that pulsant electrogenesis and spike timing coding of electrosensory signals developed concomitantly in the same species, and evolved convergently in African and American electric fish.

Highlights

Electric fish explore their surroundings with an electric field characterized by either pulsating patterns or continuous sine-waves generated by the discharge of an electric organ (EOD)
The electrosensory lobe (ESL) of pulse Gymnotiformes appears to show different signal processing rules since each pulse reclutes the network with neuron-specific post-electric organ discharge (EOD) phase preferent patterns (Pereira et al, 2014) and evokes local field potential which patterns are modulated by changes in the electrosensory environment (Pereira et al, 2005)
Spike patterns exhibited the presence of a silence between 7 to 10 ms, and 1 to 3 modes found at ca. 5, 12, or more than 23 ms after the positive peak of the EOD

Summary

Introduction

Electric fish explore their surroundings with an electric field characterized by either pulsating patterns or continuous sine-waves generated by the discharge of an electric organ (EOD). “Electric images” generated by the presence of objects are differently encoded by primary afferents (pulse evoked bursts in pulse-emitting and pseudorandom trains in wave-emitting fish). This draws clear distinctions between pulse and wave electroreception strategies (Caputi & Aguilera, 2020). The ESL of pulse Gymnotiformes appears to show different signal processing rules since each pulse reclutes the network with neuron-specific post-EOD phase preferent patterns (Pereira et al, 2014) and evokes local field potential which patterns are modulated by changes in the electrosensory environment (Pereira et al, 2005)

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