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

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Synaptic dynamics during the sleep-wake cycle are critical for brain function but remain debated.
• The Synaptic Homeostasis Hypothesis (SHY) posits synaptic depression during non-rapid eye movement (NREM) sleep.
• Contradictory findings suggest synaptic potentiation or activity-dependent changes during NREM sleep.

Purpose of the Study:

• To investigate the boundary conditions influencing contradictory observations of synaptic dynamics during sleep.
• To explore the roles of specific learning rules and neuronal firing patterns in synaptic plasticity.
• To reconcile differing hypotheses on synaptic changes across the sleep-wake cycle.

Main Methods:

• Utilized computational models of mammalian cortical neurons.
• Simulated Hebbian and Anti-Hebbian learning rules, including spike-timing dependent plasticity (STDP) and Anti-STDP.
• Analyzed synaptic weight changes under wake-like and sleep-like firing patterns.

Main Results:

• Under Hebbian/STDP, wake-like firing decreased synaptic weights, while sleep-like firing increased them (Wake Inhibition and Sleep Excitation - WISE).
• Under Anti-Hebbian/Anti-STDP, NREM sleep induced synaptic depression, supporting the SHY.
• Synaptic changes were modulated by firing rate differences between NREM sleep and wakefulness.

Conclusions:

• A unified framework is proposed to explain diverse synaptic homeodynamics observed during the sleep-wake cycle.
• The interplay between learning rules and firing patterns dictates whether synapses strengthen or depress during sleep.
• This research reconciles conflicting hypotheses on synaptic plasticity across sleep and wakefulness.