Lateralized tactile stimulation during NREM sleep globally increases both slow and fast frequency activities

Slow frequency activity during non‐rapid eye movement (NREM) sleep emerges from synchronized activity of widely distributed thalamo‐cortical and cortico‐cortical networks, reflecting homeostatic and restorative properties of sleep. Slow frequency activity exhibits a reactive nature, and can be increased by acoustic stimulation. Although non‐invasive brain stimulation is a promising technique in basic and clinical sleep research, sensory stimulation studies focusing on modalities other than the acoustic are scarce. We explored here the potential of lateralized vibro‐tactile stimulation (VTS) of the finger to locally modify electroencephalographic activity during nocturnal NREM sleep. Eight seconds‐long sequences of vibro‐tactile pulses were delivered at a rate of 1 Hz either to the left or to the right index finger, in addition to a sham condition, in fourteen healthy participants. VTS markedly increased slow frequency activity that peaked between 1–4 Hz but extended to higher (~13 Hz) frequencies, with fronto‐central dominance. Enhanced slow frequency activity was accompanied by increased (14–22 Hz) fast frequency power peaking over central and posterior locations. VTS increased the amplitude of slow waves, especially during the first 3–4 s of stimulation. Noticeably, we did not observe local‐hemispheric effects, that is, VTS resulted in a global cortical response regardless of stimulation laterality. VTS moderately increased slow and fast frequency activities in resting wakefulness, to a much lower extent compared to NREM sleep. The concomitant increase in slow and fast frequency activities in response to VTS indicates an instant homeostatic response coupled with wake‐like, high‐frequency activity potentially reflecting transient periods of increased environmental processing.