In search of optimal fear inducing stimuli: Differential behavioral responses to computer animated images in zebrafish

Abstract

Zebrafish has been gaining popularity in behavioral genetics and behavioral neuroscience as this species offers an excellent compromise between system complexity and practical simplicity for mechanistic analyses of brain and behavior function. Recently, a number of studies started to investigate methods with which fear responses may be induced reliably in zebrafish. The ultimate goal of these studies has been to develop zebrafish models of pathological processes and to investigate the mechanisms of fear and to eventually translate the findings to the human clinic. Previously, animated image of a sympatric predator of zebrafish was shown to induce fear responses. Here we expand on this recently gained knowledge and investigate whether other moving images may induce more robust fear responses. The images investigated include the original sympatric predator, the Indian leaf fish, another sympatric predator, the needle fish, a bird silhouette moved on the side or above the tank, an expanding dot mimicking rapid approach of an object shown on the side and from above the tank, as well as non-fear inducing images including a single and a group of zebrafish. Our results indicate that although the sympatric predators do induce some fear responses, the other images, particularly the expanding dot but also the bird silhouette shown from above are more effective. The results also reveal a stimulus dependent motor pattern response repertoire of zebrafish demonstrating that perhaps univariate quantification methods may not be appropriate for uncovering the complexity of fear or anxiety related phenotypical changes in this species.

Sexual dimorphisms in swimming behavior, cerebral metabolic activity and adrenoceptors in adult zebrafish (Danio rerio)

“…In the present study, the fact that female fish introduced to a novel tank test, displayed an increased locomotion along with a preference for the upper part of the tank, can be interpreted as signs of low anxiety [60] and higher boldness [61]. In contrast, a clear high initial preference of male zebrafish for the bottom part of the tank within the first few minutes of the conducted test could reflect an increased anxiety-like response, suggesting a clear sex-specific difference in the behavioral responses to a novel environment.…”

Individual differences in activity levels in zebrafish (Danio rerio)

“…Also occasionally observed in zebrafish is the initial preference for the bottom of the tank within the first few minutes of being exposed to a new place, a response that subsequently may dissipate as the fish becomes habituated to the environment [22, 30 – 31]. Notably, however, this response has been argued to be less of a reliable indicator of fear due to its context dependence [2, 23, 36]. We report no changes in depth preference in the 37 L tank over the first 7 testing days but we detected a significant habituation of activity especially robust between days 1 and 2.…”

A jump persistent turning walker to model zebrafish locomotion

“…Furthermore, with the aim of generating highthroughput behavioural data [5][6][7], considerable research is being performed to integrate computer-animated images and robotic replicas of conspecifics, heterospecifics and predators [8][9][10][11][12]. Zebrafish have been used to study the fundamental mechanisms governing the exhibition of emotional patterns [13,14], individual response to alcohol and drugs of abuse [15][16][17], and higher order brain functions, such as memory and learning [18].…”