Understanding (and appreciating) behavioral complexity of zebrafish novel tank assays

Zebrafish are rapidly becoming an important model organism in neurobehavioral research. The novel tank diving test is commonly used for assessing locomotor, anxiety-related and other behaviors in adult zebrafish. Assessing characteristic neophobic bottom preference, erratic movements and freezing/immobility behavior, the test represents a fast, easy-to-perform, single-trial novelty-based assay sensitive to pharmacological, genetic and environmental manipulations. Here, we critically evaluate key behavioral parameters in the novel tank test, and multiple intrinsic and extrinsic factors that affect the assessment of fish behavioral phenotypes, including habituation, homebase, social behaviors, stress responses, novelty/familiarity and personality traits. We also discuss the value of this assay for modeling a broad spectrum of brain phenomena, including generalized anxiety, fear, panic-like, post-traumatic stress- and depression-like behavior. Overall, the emerging behavioral complexity of the novel tank test extends beyond the traditional dichotomic conflict between fear and exploration, likely reflecting multiple overlapping neurobehavioral domains in zebrafish.