# A unified framework to model synaptic dynamics during the sleep–wake cycle

## TL;DR

This study explains how synaptic strength changes during sleep and wakefulness using a computational model, resolving conflicting observations about synaptic dynamics.

## Contribution

The study introduces a unified framework called WISE to explain synaptic homeodynamics during the sleep–wake cycle.

## Key findings

- Wake-like firing patterns decrease synaptic weights under Hebbian and STDP rules.
- Sleep-like firing patterns strengthen synaptic weights under Hebbian and STDP rules.
- Synaptic depression during NREM sleep aligns with SHY under Anti-Hebbian and Anti-STDP rules.

## Abstract

Understanding synaptic dynamics during the sleep–wake cycle in the cortex is crucial yet remains controversial. The synaptic homeostasis hypothesis (SHY) suggests synaptic depression during non-rapid eye movement (NREM) sleep, while other studies report synaptic potentiation or synaptic changes during NREM sleep depending on activities in wakefulness. To find boundary conditions between these contradictory observations, we focused on learning rules and firing patterns that contribute to the synaptic dynamics. Using computational models considering mammalian cortical neurons, we found that under Hebbian and spike-timing dependent plasticity (STDP), wake-like firing patterns decrease synaptic weights, while sleep-like patterns strengthen synaptic weights. We refer to this tendency as Wake Inhibition and Sleep Excitation (WISE). Conversely, under Anti-Hebbian and Anti-STDP, synaptic depression during NREM sleep was observed, aligning with the conventional synaptic homeostasis hypothesis. Moreover, synaptic changes depended on firing rate differences between NREM sleep and wakefulness. We provide a unified framework that could explain synaptic homeodynamics under the sleep–wake cycle.

Conflicting results have been observed regarding changes in synaptic strength in the cerebral cortex during the sleep-wake cycle. This computational study provides a comprehensive understanding and unified framework about synaptic dynamics during the sleep-wake cycle.