Imperceptible Somatosensory Single Pulse and Pulse Train Stimulation Oppositely Modulate Mu Rhythm Activity and Perceptual Performance

Abstract

Subliminal stimulation alters conscious perception – a potential mechanism is the modulation of cortical background rhythms especially in the alpha range. Here, in the human somatosensory domain, we assessed effects of subthreshold (imperceptible) electrical finger nerve stimulation – either presented as single pulses or as brief (1 s) 7 Hz pulse trains—on mu-alpha rhythm and perceptual performance. In electroencephalography, subthreshold single pulses transiently (~150–350 ms poststimulus) increased mu activity (event-related synchronization), while, interestingly, subthreshold trains led to prolonged (>1 s) mu desynchronization. In psychophysics, detection of near-threshold target stimuli was consistently reduced when presented together with subthreshold trains (at three delays), whereas for targets paired with subthreshold single pulses detection remained unaffected (30 and 180 ms) or was even elevated (60 ms). Though both imperceptible, single pulses and pulse trains exerted opposite effects on neural signaling and perception. We suggest that the common neural basis is preferential activation of cortical inhibitory interneurons. While the inhibitory impact of a subthreshold single pulse (reflected by mu synchronization) is not psychophysically detectable—rather perception may be facilitated—repetition of the same subthreshold pulse shifts the excitation-inhibition balance toward an inhibitory cortical state (reflected by perceptual impediment) accompanied by mu desynchronization. These differential findings provide novel insights on the notion of alpha activity mediating functional inhibition.

Surround Inhibition Mediates Pain Relief by Low Amplitude Spinal Cord Stimulation: Modeling and Measurement

“…A study of continuous 50-Hz subperception SCS found decreased mechanical hypersensitivity and altered theta rhythms in awake freely moving rats ( Koyama et al, 2018 ). Finally, electroencephalography (EEG) recordings during electrical stimulation below PT indicated that stimulation can have significant direct effects on somatosensory responses without evoking perception ( Iliopoulos et al, 2020 ).…”

Novel Technologies Targeting the Rehabilitation of Neurological Disorders

“…The acquired EEG signals will be analyzed offline using MATLAB2013b. Given previous evidence that oscillatory dynamics are affected by rTMS (Thut et al, 2011;Veniero et al, 2011;Chota et al, 2021) and are closely related to cognitive improvement (Klimesch et al, 1993;Richard Clark et al, 2004;Iliopoulos et al, 2020), we will analyze the power spectrum and functional connectivity of each oscillation within and between hemispheres, between groups, and pre-and post-treatment. Oscillation ratios, such as θ/α ratio, θ/γ ratio, and (α + β)/(θ + δ) ratio will be further analyzed (Coben et al, 1985;Moretti et al, 2013;Sato et al, 2022).…”

Intermittent theta burst stimulation vs. high-frequency repetitive transcranial magnetic stimulation for post-stroke cognitive impairment: Protocol of a pilot randomized controlled double-blind trial

“…The acquired EEG signals will be analyzed offline using MATLAB2013b. Given previous evidence that oscillatory dynamics are affected by rTMS (Thut et al, 2011;Veniero et al, 2011;Chota et al, 2021) and are closely related to cognitive improvement (Klimesch et al, 1993;Richard Clark et al, 2004;Iliopoulos et al, 2020), we will analyze the power spectrum and functional connectivity of each oscillation within and between hemispheres, between groups, and pre-and post-treatment. Oscillation ratios, such as θ/α ratio, θ/γ ratio, and (α + β)/(θ + δ) ratio will be further analyzed (Coben et al, 1985;Moretti et al, 2013;Sato et al, 2022).…”