Cellular coupling determines scale-invariant behavior of neurons in suprachiasmatic nucleus

Abstract

The main clock in mammals, located in the suprachiasmatic nucleus (SCN) of hypothalamus, not only regulates the daily rhythms in physiological and behavioral activities, but also plays a key role as one of the control nodes in the brain regulating behavioral activity. As such, it induces scaleinvariance in the temporal patterns of behavioral activity and of multi-unit neural activity of the SCN network. In particular, the scale-invariant patterns maintain across multiple time scales from 3 minutes to 10 hours, characterized by a scaling exponent around 1. Thus far, no study found the origin of the scale-invariance of the SCN network. Using the method of correlation-dependent balance estimation of diffusion entropy (cBEDE), we found that scale-invariance also exists in the individual neurons of the SCN, and the scale invariance properties are significantly increased when the neurons are coupled in a network of neurons. Improved scale invariance in the single neurons is, therefore, imposed by the emergent network properties of the SCN network. Our findings show that the scale-invariance of the SCN can already be found at the level of the individual neurons and that the application of a scale invariance measure, such as cBEDE, can help in determining the network status of the SCN.

Network Structure of the Master Clock Is Important for Its Primary Function

“…TTX is known to completely abolish intercellular coupling between neurons. After the application of the TTX to a brain slice, the synchronization between neurons is deteriorated since the coupling through the neurotransmitters is blocked, leading also to a reduction of the amplitudes of single neurons (Yamaguchi et al, 2003;Abel et al, 2017;Zhou et al, 2020). Removal of the TTX leads to the restoration of the synchronization and the amplitudes.…”

Light-induced synchronization of the SCN coupled oscillators and implications for entraining the HPA axis

“…Although the specific mechanisms of different neurotransmitters might be different, those neurotransmitters are speculated to regulate neurons through a mutual coupling mechanism ( 20 , 21 ), where they are released in a circadian fashion and exhibit feedback on the clock genes. The SCN’s function is dependent on the collective activity of the neurons and the inter-neuronal coupling ( 12 , 22 ). Evidence for the SCN heterogeneity has led to various mathematical models of its network ( 21 , 23 , 24 ).…”