Sleep deprivation impairs cognitive performance in zebrafish: A matter of fact?

The zebrafish (Danio rerio) has become a valuable model organism for behavioral studies examining learning and memory. Its diurnal circadian rhythm and characterized sleep-like state make it comparable to mammals, features that have contributed to establishing this small vertebrate as a translational model for sleep research. Despite sleep being an evolutionarily conserved behavior, its mechanisms and functions are still debated. Sleep deprivation is commonly associated with decreased attention, reduced responsiveness to external stimuli, altered locomotor activity and impaired performance on cognitive tasks. In the current study, we examined the effects of partial and total sleep deprivation on zebrafish learning performance in an active avoidance conditioning paradigm. In addition, we examined the effects of two drugs known to alter sleep (alcohol and melatonin) on learning performance in sleep deprived animals. Our results suggest that although partial sleep deprivation did not alter learning performance, total sleep deprivation was found to significantly impair behavioral responses to the electric shock as well as avoidance learning. However, when sleep deprived fish were treated with alcohol the night before the learning task, learning performance was similar to the control group. In contrast, melatonin treatment did not alter learning performance in sleep deprived animals. We conclude that the zebrafish is a sensitive tool for investigating the effects of sleep deprivation on cognitive performance and may be a useful model for dissecting the mechanisms underlying learning and memory.