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Background/Objectives:: The link between serotonergic modulation and depression is under debate; however, serotonin reuptake inhibitors (SRIs) are still the first-choice medicine in this condition. Disturbances in time perception are also reported in depression with one of the behavioral schedules used to study interval timing, differential-reinforcement-learning-of-low-rate, having been shown to have high predictive validity for an antidepressant effect. Here, we introduce an IntelliCage research protocol of an interval bisection task that allows more ecologically valid and less time-consuming rodent examination and provides an example of its use to confirm the previously reported acute effect of an SRI, clomipramine, on interval timing (increase in bisection point, D50). Methods: Wistar male rats (n = 25, five groups of 5–8) were trained in the IntelliCage to discriminate between short (1 s) and long (4 s) LED light stimuli by nose poking at the corresponding (left/right) side of the IntelliCage chamber to obtain a drink. When 80% of correct responses were reached, the intermediate durations of 1.7, 2.5, and 3.3 s were introduced. The number of left/right choices for each stimulus and interval timing parameters (bisection point, D50, and timing precision), derived from them, were compared after saline and clomipramine (7 mg/kg, i.p) intraperitoneal administration. Results: Rats successfully learned the task within about a week of training. The slightly increased D50 after clomipramine confirmed previous studies. Conclusions: The introduced protocol has potential to be applicable to preclinical research on depression and potentially other psychopathology, where time perception can be disturbed. [ABSTRACT FROM AUTHOR]

Time perception is a fundamental cognitive function essential for adaptive behavior and shared across species. The neural mechanisms underlying time perception, particularly its neuromodulation, remain debated. In this review, we examined the role of the serotonergic system in time perception (at the scale of seconds and minutes), building a translational bridge between human and non-human animal studies. The literature search was conducted according to the PRISMA statement in PubMed, APA PsycINFO, and APA PsycARTICLES. Sixty papers were selected for full-text review, encompassing both human (n = 10) and animal studies (n = 50). Summarizing the reviewed literature, we revealed consistent evidence for the role of serotonin in timing behavior, highlighting its complex involvement across retrospective, immediate, and prospective timing paradigms. Increased serotonergic activation appears to accelerate internal time speed, which we interpret through the dual klepsydra model as accelerated discharge of the temporal accumulator. However, some findings challenge this framework. Additionally, we link impulsivity—associated with decreased serotonergic functioning in our review—to a slower internal time speed. Variability in prospective timing tasks underscores the need for further research into how serotonin modulates reward-based temporal decisions, using novel approaches to disentangle internal time speed, response inhibition, and other factors. [ABSTRACT FROM AUTHOR]