Data-driven modelling of social forces and collective behaviour in zebrafish.

Zebrafish are rapidly emerging as a powerful model organism in hypothesis-driven studies targeting a number of functional and dysfunctional processes. Mathematical models of zebrafish behaviour can inform the design of experiments, through the unprecedented ability to perform pilot trials on a computer. At the same time, in-silico experiments could help refining the analysis of real data, by enabling the systematic investigation of key neurobehavioural factors. Here, we establish a data-driven model of zebrafish social interaction. Specifically, we derive a set of interaction rules to capture the primary response mechanisms which have been observed experimentally. Contrary to previous studies, we include dynamic speed regulation in addition to turning responses, which together provide attractive, repulsive and alignment interactions between individuals. The resulting multi-agent model provides a novel, bottom-up framework to describe both the spontaneous motion and individual-level interaction dynamics of zebrafish, inferred directly from experimental observations.

Sociality modulates the effects of ethanol in zebra fish.

BACKGROUND: The complex social behavior exhibited by zebra fish is often leveraged in preclinical studies to investigate whether and how psychoactive compounds modulate inter individual interactions. Due to theoretical and methodological constraints, previous studies on the effects of ethanol (EtOH) on social behavior focused on homogeneous groups in which all individuals were treated, thereby limiting the possibility of isolating all the intervening variables. METHODS: To identify how a social group affects the individual response to EtOH, we quantified the behavior of a single treated individual (acute 0.00, 0.25, 0.50, and 1.00% concentration/volume) swimming together with a group of untreated subjects or alone. A novel in-house-developed automated tracking system was utilized to extract the trajectories of each subject and analyze individual and social behavior. Specifically, we characterized the locomotion of each individual, the cohesion and degree of alignment of the group of untreated subjects, and the interaction between treated and untreated subjects. RESULTS: Individual response to high EtOH concentrations varied depending on the presence or absence of conspecifics. Specifically, EtOH-exposed subjects swam faster when group-tested than in isolation. Remarkably, the presence of the exposed individual substantially influenced the behavior of the untreated subjects. Thus, untreated subjects swam faster when the treated individual was exposed to intermediate EtOH concentrations, without varying their cohesion and degree of alignment. No change in the distance between treated and untreated subjects was found; however, the likelihood that the swimming direction of the treated individual anticipated the response of the group was influenced by EtOH concentration. CONCLUSIONS: Our results demonstrate the feasibility of exposing a single individual to EtOH and test it together with untreated subjects. This approach has the potential to unravel the social determinants of individual response to alcohol, by enabling us to dissociate EtOH exposure from sociality.

Acute caffeine administration affects zebrafish response to a robotic stimulus.

Zebrafish has been recently proposed as a valid animal model to investigate the fundamental mechanisms regulating emotional behavior and evaluate the modulatory effects exerted by psychoactive compounds. In this study, we propose a novel methodological framework based on robotics and information theory to investigate the behavioral response of zebrafish exposed to acute caffeine treatment. In a binary preference test, we studied the response of caffeine-treated zebrafish to a replica of a shoal of conspecifics moving in the tank. A purely data-driven information theoretic approach was used to infer the influence of the replica on zebrafish behavior as a function of caffeine concentration. Our results demonstrate that acute caffeine administration modulates both the average speed and the interaction with the replica. Specifically, zebrafish exposed to elevated doses of caffeine show reduced locomotion and increased sensitivity to the motion of the replica. The methodology developed in this study may complement traditional experimental paradigms developed in the field of behavioral pharmacology.

Live predators, robots, and computer-animated images elicit differential avoidance responses in zebrafish.

Emotional disturbances constitute a major health issue affecting a considerable portion of the population in western countries. In this context, animal models offer a relevant tool to address the underlying biological determinants and to screen novel therapeutic strategies. While rodents have traditionally constituted the species of choice, zebrafish are now becoming a viable alternative. As zebrafish gain momentum in biomedical sciences, considerable efforts are being devoted to developing high-throughput behavioral tests. Here, we present a comparative study of zebrafish behavioral response to fear-evoking stimuli offered via three alternative methodologies. Specifically, in a binary-choice test, we exposed zebrafish to an allopatric predator Astronotus ocellatus, presented in the form of a live subject, a robotic replica, and a computer-animated image. The robot's design and operation were inspired by the morphology and tail-beat motion of its live counterpart, thereby offering a consistent three-dimensional stimulus to focal fish. The computer-animated image was also designed after the live subject to replicate its appearance. We observed that differently from computer-animated images, both the live predator and its robotic replica elicited robust avoidance response in zebrafish. In addition, in response to the robot, zebrafish exhibited increased thrashing behavior, which is considered a valid indicator of fear. Finally, inter-individual response to a robotic stimulus is more consistent than that shown in response to live stimuli and animated images, thereby increasing experimental statistical power. Our study supports the view that robotic stimuli can constitute a promising experimental tool to elicit targeted behavioral responses in zebrafish.