Reduced Plasticity in Coupling Strength in the Aging SCN Clock as Revealed by Kuramoto Modeling

Area of Science:

• Neuroscience
• Chronobiology
• Systems Biology

Background:

• The mammalian circadian clock, centered in the suprachiasmatic nucleus (SCN), synchronizes to the light-dark cycle.
• Neuronal communication within the SCN is crucial for adapting to seasonal photoperiod changes.
• Aging diminishes the ability to adjust behaviorally to these seasonal shifts, with underlying mechanisms unclear.

Purpose of the Study:

• To investigate how aging affects the SCN's neuronal coupling plasticity in response to varying photoperiods.
• To understand the mechanisms behind reduced seasonal adaptation in elderly individuals.

Main Methods:

• Analysis of PERIOD2::LUCIFERASE (PER2::LUC) expression rhythms in SCN neurons of young and old mice.
• Entrainment of mice to long (LP) and short (SP) photoperiods.
• Application of a 2-community noisy Kuramoto model to assess neuronal coupling strength and phase coherence.

Main Results:

• SCN neuronal coupling strength correlates with photoperiod-induced phase relationships.
• Young mice exhibit adaptable coupling: weak in LP, strong in SP.
• Aged mice show weak coupling in LP but a diminished capacity to strengthen coupling in SP.

Conclusions:

• The reduced ability of aged SCN neurons to increase coupling strength in short photoperiods contributes to deficits in seasonal behavioral adaptation.
• Photoperiod manipulation may not be an effective strategy to enhance circadian clock function in aging.