Noise induces oscillation in the two weakly coupled subgroups of the suprachiasmatic nucleus
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ORIGINAL PAPER
Noise induces oscillation in the two weakly coupled subgroups of the suprachiasmatic nucleus Jiahui Li · Changgui Gu
· Huijie Yang
Received: 19 August 2020 / Accepted: 15 October 2020 © Springer Nature B.V. 2020
Abstract In mammals, the main clock regulating the circadian rhythms is located in the suprachiasmatic nucleus (SCN) of the brain. The SCN is composed of about 20,000 synchronized neuronal oscillators and can be divided into two subgroups, named the ventrolateral part (VL) and the dorsomedial part (DM). The circadian rhythms of the SCN output depend on the cellular coupling. If the cellular coupling is reduced, the circadian rhythm of the SCN is lost because the rhythms of the individual neurons are lost. In the present study, we examine whether the lost rhythms of the SCN with the reduced coupling can be restored by the intrinsic noise to the neurons. Based on a modified Goodwin model, both the simulations and the analyses show that the rhythms of the SCN can be restored by the noise when the VL and the DM are weakly coupled. Our finding provides a method to restore the lost rhythms of the SCN and shed light on the influence of noise on the collective behaviors of the SCN. Keywords Noise · Weak coupling · Amplitude · Circadian clock Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11071-020-06034-2) contains supplementary material, which is available to authorized users. J. Li · C. Gu (B) · H. Yang Department of Systems Science, University of Shanghai for Science and Technology, Shanghai 200093, China e-mail: [email protected]
1 Introduction The suprachiasmatic nucleus (SCN) in the brain serves as a main clock in mammals [1,2], which has two main functions, i.e., it not only synchronizes the body rhythms to the external light–dark cycle (entrainment) [3,4], but also can produce robust rhythmic signals of endogenous periods that are around but not exact 24 h to regulate the body rhythms under the constant darkness (free running) [5,6]. The main functions may be deteriorated under special conditions, e.g., the robust rhythms are disrupted in ageing mice [7] or under long photoperiod [8]. The SCN is composed of about 20,000 synchronized neuronal oscillators [9]. These neurons are divided into two subgroups, one named the VL (ventrolateral part) where the neurons are sensitive to the light information from the retina and the other is the DM (dorsomedial part) where the neurons are insensitive to the light information and receive the coupling from the VL [10,11]. The coupling between the VL and the DM is asymmetrical, i.e., the VL dominates the DM or the coupling strength from the VL to the DM is larger than the other direction [12]. This asymmetry can be explained by the distribution of the neurotransmitters that play roles in the coupling. In particular, VIP are produced by the neurons in the VL and absorbed by the neurons in the DM. The AVP are secreted by the neurons in the DM. The VL and the DM are connected by the GABA [13– 15].
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