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Updated: May 22, 2026

Somatosensory Event-related Potentials from Orofacial Skin Stretch Stimulation
Published on: December 18, 2015
Are high-frequency (600 Hz) oscillations in human somatosensory evoked potentials due to phase-resetting phenomena?
Gunnar Waterstraat1, Bartosz Telenczuk, Martin Burghoff
1Neurophysics Group, Department of Neurology, Campus Benjamin Franklin, Charite-University Medicine Berlin, Berlin, Germany. gunnar.waterstraat@charite.de
Objective:
Median nerve somatosensory evoked potentials (SEP) contain a brief oscillatory wavelet burst at about 600 Hz (σ-burst) superimposed on the initial cortical component (N20). While invasive single-cell recordings suggested that this burst is generated by increased neuronal spiking activity in area 3b, recent non-invasive scalp recordings could not reveal concomitant single-trial added-activity, suggesting that the SEP burst might instead be generated by phase-reset of ongoing high-frequency EEG. Here, a statistical model and exemplary data are presented reconciling these seemingly contradictory results.
Methods:
A statistical model defined the conditions required to detect added-activity in a set of single-trial SEP. Its predictions were tested by analyzing human single-trial scalp SEP recorded with custom-made low-noise amplifiers.
Results:
The noise level in previous studies did not allow to detect single-trial added-activity in the period concomitant with the trial-averaged σ-burst. In contrast, optimized low-noise recordings do reveal added-activity in a set of single-trials.
Conclusions:
The experimental noise level is the decisive factor determining the detectability of added-activity in single-trials. A low-noise experiment provided direct evidence that the SEP σ-burst is at least partly generated by added-activity matching earlier invasive single-cell recordings.
Significance:
Quantitative criteria are provided for the feasibility of single-trial detectability of band-limited added-activity.
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