The dual-process model: Unlocking the potential of auditory stimulation to modulate brain oscillations during sleep

Slow waves and spindles, key electrophysiological markers of non-rapid eye movement (NREM) sleep, are thought to play a causal role in sustaining brain functions. While their association with these functions has been recognized for decades, the underlying mechanisms remain elusive. Emerging evidence suggests that their functional role is defined not only by individual oscillations but also by the interplay of spatiotemporal neuronal synchronization. Recent studies modulating NREM sleep oscillations through auditory input have demonstrated direct behavioral effects, enabling new diagnostic and therapeutic tools for psychiatric and neurological disorders. However, clinical translation remains limited due to an incomplete understanding of the neuronal mechanisms. Here, we propose a new conceptual framework for auditory stimulation during NREM sleep, outlining how key stimulation parameters influence the spatiotemporal coordination of network activities underlying specific oscillations. This framework provides a foundation for interpreting the effects of auditory stimulation, formulating hypotheses on neuronal mechanisms, and identifying which synchronization processes to target for specific functions. Such foundational understanding is a prerequisite for establishing the causal role of distinct synchronization processes of NREM sleep oscillations in driving diverse brain functions - a critical step toward effectively applying and clinically translating brain stimulation techniques beyond auditory stimulation during NREM sleep.