Modeling the variability of the electromotor commandsystem of pulse electric fish

Abstract

Mormyrids, a family of weakly electric fish, use electric pulses for communication and for extracting information from the environment (active electroreception). The electromotor system controls the timing of pulse generation. Ethological studies have described several sequences of pulse intervals (SPIs) which are related to distinct behaviors (e.g. mating or exploratory behaviors). Accelerations, scallops, rasps, and cessations are four SPI patterns reported in these fish, each showing characteristic temporal structures and large variability. This paper presents a computational model of the electromotor command circuit that reproduces SPI patterns as a function of the inputs to the model while keeping the same internal network configuration. The topology of the model is based on a simplified representation of the network with four neuron clusters (nuclei). An initial ad hoc tuned configuration (S-T) was built to reproduce nucleus characteristics and network topology as described by detailed morphological and electrophysiological studies. Then, a genetic algorithm (GA) was developed and applied to automatically tune the synaptic parameters of the model connectivity. Two different configurations obtained from the GA are presented here: one optimized to a set of synthetic examples of SPI patterns (S-GA) and another configuration adjusted to patterns recorded from freely-behaving Gnathonemus Petersii specimens (R-GA). Robustness analyses to input variability were performed to discard overfitting and assess validity. Results show that the set of SPI patterns are consistently reproduced, both for synthetic data and for recorded data. This model can be used as a tool to test novel hypotheses regarding temporal structure in electrogeneration.