Triggering sleep slow waves by transcranial magnetic stimulation

TLDR

During sleep, cortical neurons exhibit near‑synchronous slow oscillations that generate the prominent slow waves and spindles seen in the EEG. The study demonstrates that transcranial magnetic stimulation can reliably evoke slow waves and spindles during sleep. Using sub‑1 Hz TMS pulses with specific parameters, each pulse elicits a high‑amplitude slow wave that originates beneath the coil and propagates across the cortex. TMS‑evoked slow waves expose intrinsic bistability in thalamocortical networks during NREM sleep and deepen sleep by increasing slow‑wave activity, potentially supporting brain restoration and memory consolidation.

Abstract

During much of sleep, cortical neurons undergo near-synchronous slow oscillation cycles in membrane potential, which give rise to the largest spontaneous waves observed in the normal electroencephalogram (EEG). Slow oscillations underlie characteristic features of the sleep EEG, such as slow waves and spindles. Here we show that, in sleeping subjects, slow waves and spindles can be triggered noninvasively and reliably by transcranial magnetic stimulation (TMS). With appropriate stimulation parameters, each TMS pulse at <1 Hz evokes an individual, high-amplitude slow wave that originates under the coil and spreads over the cortex. TMS triggering of slow waves reveals intrinsic bistability in thalamocortical networks during non-rapid eye movement sleep. Moreover, evoked slow waves lead to a deepening of sleep and to an increase in EEG slow-wave activity (0.5-4.5 Hz), which is thought to play a role in brain restoration and memory consolidation.