Line Plot from Scientific Research

This model proposes that the physiological processes driven by NA fluctuations during NREM sleepspecifically those related to memory consolidation and glymphatic clearanceare optimal when NA fluctuations occur approximately every 50 s. The inverted U-shaped curve suggests that there is a delicate balance between LC activity, NA fluctuations, and MA frequency, with both insufficient and excessive fluctuations leading to suboptimal outcomes. On the left side of the curve, reduced LC activity will attenuate NA fluctuations and decrease MA frequency, which may impair sleeps restorative functions, including memory consolidation and brain clearance. On the right side, elevated LC activity increases MA frequency, causing excessive fragmentation of sleep. Such abundance of MAs will disrupt the orderly progression of sleep-dependent plasticity and restorative processes, contributing to daytime sleepiness and potentially leading to long-term adverse health effects. While excessive MAs are known to fragment sleep and impair cognitive function, their specific impact on glymphatic clearance remains an open question requiring further investigation. The model underscores the importance of maintaining an optimal range of NA fluctuations and MA frequency to preserve the full spectrum of sleep benefits. Both extremeswhether through reduced or excessive NA fluctuationsare predicted to have negative consequences for the essential restorative processes of NREM sleep.

DOI