Poster presentation from Twentieth Annual Computational Neuroscience Meeting: CNS*2011. Stockholm, Sweden. 23-28 July 2011This work was supported by grants MICINN BFU2009-08473 and TIN 2010- 19607, Spanish-Brazilian Cooperation PHB2007-0008 and Brazilian agencies FAPESP, CNPq and CAPES

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Electric fishes modulate their electric organ discharges with a remarkable variability. Some patterns can be easily identified, such as pulse rate changes, offs and chirps, which are often associated with important behavioral contexts, including aggression, hiding and mating. However, these behaviors are only observed when at least two fish are freely interacting. Although their electrical pulses can be easily recorded by non-invasive techniques, discriminating the emitter of each pulse is challenging when physically similar fish are allowed to freely move and interact. Here we optimized a custom-made software recently designed to identify the emitter of pulses by using automated chirp detection, adaptive threshold for pulse detection and slightly changing how the recorded signals are integrated. With these optimizations, we performed a quantitative analysis of the statistical changes throughout the dominance contest with respect to Inter Pulse Intervals, Chirps and Offs dyads of freely moving Gymnotus carapo. In all dyads, chirps were signatures of subsequent submission, even when they occurred early in the contest. Although offs were observed in both dominant and submissive fish, they were substantially more frequent in submissive individuals, in agreement with the idea from previous studies that offs are electric cues of submission. In general, after the dominance is established the submissive fish significantly changes its average pulse rate, while the pulse rate of the dominant remained unchanged. Additionally, no chirps or offs were observed when two fish were manually kept in direct physical contact, suggesting that these electric behaviors are not automatic responses to physical contact.

Dedicated systems are fundamental for neuroscience experimental protocols that require timing determinism and synchronous stimuli generation. We developed a data acquisition and stimuli generator system for neuroscience research, optimized for recording timestamps from up to 6 spiking neurons and entirely specified in a high-level Hardware Description Language (HDL). Despite the logic complexity penalty of synthesizing from such a language, it was possible to implement our design in a low-cost small reconfigurable device. Under a modular framework, we explored two different memory arbitration schemes for our system, evaluating both their logic element usage and resilience to input activity bursts. One of them was designed with a decoupled and latency insensitive approach, allowing for easier code reuse, while the other adopted a centralized scheme, constructed specifically for our application. The usage of a high-level HDL allowed straightforward and stepwise code modifications to transform one architecture into the other. The achieved modularity is very useful for rapidly prototyping novel electronic instrumentation systems tailored to scientific research.

Weakly electric fish's ability to communicate through a self-generated electric field has attracted attention from several areas of knowledge for more than 50 years. Particularly, pulse-type electric fish emit signals that exhibits several similarities with neuronal spike trains, becoming a popular animal model in neuroscience. Due to the increase of computational power and the development of new machine learning tools, it is now possible to investigate dominance interactions between a pair of fish at the level of every single pulse. As far as we know, information is coded and transmitted by modulation of interval between pulses. Thus, communication between electric fishes presents several similarities with the communication between neurons from different regions on the central nervous system: the spike rate of one neuron is modulated by the pulses emitted by the other. Here we investigated the social interactions between pairs of Gymnotus carapo, a highly territorial species. Using time series analysis, machine learning techniques, and information theory, we developed a methodology to identify communicative patterns in the pulses emitted by the fish. In addition, we observed a causal relation on the pattern emission: only one of the fish modifies the future behavior of its conspecific. This flow of information seems to be related to the dominance/submission role assumed by each individual. From the literature on the physiology of the emission of new pulses, we developed new hypotheses about the functioning of the neural systems responsible for modulating the intervals between pulses and on how these systems can be modified by hormones secreted during a dominance contest.

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