*Corresponding authors e-mail: bsbgfatec@hotmail.com Introduction: The coordinated activity of multiple oscillators in the suprachiasmatic nuclei (SCN) regulates mammalian physiology and mediates entrainment of circadian rhythms to daily light-dark cycles. Some studies have shown that long photoperiods reduce the coupling between ventral region (VR) neurons, whereas dorsal region (DR) neurons broaden the duration of their activity. In this work we aimed to describe, by means of mathematical modeling, the spatiotemporal characteristics of the circadian rhythm in the SCN. Methods: A mathematical model composed of two groups (VR e DR) of coupled oscillators was developed by using different photoperiods. A decreased coupling between the oscillators simulated the effect of light observed experimentally in the VR and in the DR. The oscillators were entrained by the mean field of the VR output. The free running period was set near 24 h. Results: (i) In constant illumination, an arrhythmicity in global output was observed, (ii) in constant dark the rhythm free ran, (ii) in a 12/12 LD cycle the VR and DR synchronized with different acrophases, (iii) during the course of a 10/10 LD cycle, the VR synchronized to light and the DR free ran, (iv) an increased light period reduced the coupling in the VR increasing the duration of the global activity, (v) the increased light period increased the duration of the oscillators’ individual activity in the DR. Conclusion: This model of spatiotemporal organization of the SCN was efficient to reproduce the main experimental results already described in many studies and can serve as a basis for the construction of new experiments to help unravel the effects of photoperiod in the coupling. Support: CNPq, FAPERN. 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
Gonçalves et al. (Thu,) studied this question.