Circadian Modulation of Interval Timing in Mice

*Corresponding author e-mail: pagostino@unq.edu.ar Timing and time perception are fundamental to survival and goal reaching in humans and other animals. To deal with timing, organisms have developed multiple systems that are active over a range of 10 orders of magnitude, the most important being circadian timing, interval timing and millisecond timing. The circadian pacemaker is located in the suprachiasmatic nuclei (SCN) of the hypothalamus, and is driven by a self-sustaining oscillator with a period near to 24 h. The estimation of time in the second-to-minutes range — known as interval timing — involves the interaction of the basal ganglia and the prefrontal cortex. There are several evidences indicating a possible link between circadian and interval timing. In this work we tested the hypothesis that interval timing is sensitive to circadian modulations. The ability of mice to estimate time intervals of short duration was examined. Animals were trained following the peak-interval (PI) procedure. Briefly, mice were trained in three consecutive phases - pre-training, fixed interval training and peak interval training. Two independent experiments were conducted, in which mice were trained in the middle of the diurnal phase (ZT 5-7) or in the middle of the nocturnal phase (ZT 17-19). Results show significant differences in the estimation of 24-second intervals at different times of day, being more accurate the group trained at night. Interval timing was also studied in animals under constant light (LL) conditions, which abolish circadian activity and temperature rhythms. Mice under LL conditions were unable to acquire temporal control in the peak interval procedure. Taken together, our results indicate a connection between the circadian system and the interval timer. Currently we are studying the estimation of time throughout the circadian cycle, as well as interval timing in animals subjected to circadian desynchronizations. We also aim to develop theoretical models which tell about the mechanisms involved in interval timing. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil