Journal: Cerebral Cortex (New York, NY)

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

doi: 10.1093/cercor/bhaa185

Figure Lengend Snippet: Schematic overview of experimental procedures. Electrophysiology: acquisition of an extended 32-channel EEG (40 subjects) during electrical nerve stimulation of the left index finger with subthreshold single current pulses (red), brief (1 s) subthreshold current pulse trains (eight pulses at 7 Hz, blue), as well as—to maintain attentional level—suprathreshold single pulses ( green ) in a pseudo-randomized order. Each subthreshold stimulation epoch was sorted offline according its pre-trial history (labeled, e.g., “single after train”, SaT), that is, whether it was presented after a subthreshold single pulse or pulse train. C4 electrode signal time courses underwent preprocessing, segmentation, and averaging (SEPs) as well as TFA. Psychophysics: Subthreshold single pulse or pulse train (1 s at 7 Hz) stimulation was combined with presentation of near-threshold TPs at different delays (30 ms, 60 ms, and 180 ms), resulting in six different conditions that were compared to the control condition (i.e., TP presentation without any subthreshold stimulation) in separate experiments (A1 to A3 and B1 to B3). In experiments B4 and B5, the TP was delivered after the fifth subthreshold pulse of the train (i.e., embedded in the train). In experiment B3, the target was delivered 180 ms after the last subthreshold pulse. The paradigm drawings are displayed out of scale for illustration purposes. Subjects’ responses were recorded (button press) in a simple detection task.

Article Snippet: When sorting the single pulse time-frequency analyses (TFAs) according to the past trial, we observe differential changes in the alpha frequency band: When averaging only the events following single pulse stimulation (SaS; ), a synchronization pattern emerges ~ 200 ms after stimulus onset and continues up to > 300 ms (similar to what we have initially expected based on our previous studies; ; ), whereas trials following subthreshold train stimulation (SaT; ) are associated with a poststimulus desynchronization from ~ 250 to > 300 ms.

Techniques: Labeling, Control

Journal: Cerebral Cortex (New York, NY)

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

doi: 10.1093/cercor/bhaa185

Figure Lengend Snippet: TFA for subthreshold single pulse stimulation. ( A ) Average from all trials does not show any significant change in EEG frequency spectrum. ( B ) Averages from respective trials after pre-trial sorting: “single pulse after single pulse” (SaS, upper panel) and “single pulse after pulse train” (SaT, lower panel). Bottom: Nonparametric statistical analysis (contrasting SaS vs. SaT) reveals a significant cluster according to the expected rhythm change at ~ 200 ms poststimulus. The window for statistical comparison was chosen a priori based on previous findings ( Nierhaus et al. 2015 ). Right column: topographic maps of the significant cluster (14–17 Hz, 270–370 ms; as determined by the above-mentioned nonparametric test) for SaS and SaT conditions, as well as their difference (for illustration purposes only, without statistical testing).

Article Snippet: When sorting the single pulse time-frequency analyses (TFAs) according to the past trial, we observe differential changes in the alpha frequency band: When averaging only the events following single pulse stimulation (SaS; ), a synchronization pattern emerges ~ 200 ms after stimulus onset and continues up to > 300 ms (similar to what we have initially expected based on our previous studies; ; ), whereas trials following subthreshold train stimulation (SaT; ) are associated with a poststimulus desynchronization from ~ 250 to > 300 ms.

Techniques: Comparison

Journal: Cerebral Cortex (New York, NY)

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

doi: 10.1093/cercor/bhaa185

Figure Lengend Snippet: TFA for subthreshold pulse train stimulation. ( A ) Average from all subthreshold train stimulations (unsorted trials; upper panel). In the nonparametric statistical analysis (comparison of the 100 ms–2 s window against baseline, i.e., –200 ms to 0 ms; lower panel), a single significant cluster (inlay) is specified. ( B ) TFAs for subthreshold pulse train stimulation after pre-trial sorting: “train after single pulse” (TaS, upper panel) and “train after train” (TaT, lower panel). Both show a decrease in the mu-alpha range emerging during train stimulation and lasting for ~ 1 s after (not significant in cluster analysis). Right: Topographic maps of the significant cluster (10–14 Hz, 600–1000 ms; as determined by the nonparametric test in A ) for all trials and after pre-trial sorting (TaS and TaT).

Article Snippet: When sorting the single pulse time-frequency analyses (TFAs) according to the past trial, we observe differential changes in the alpha frequency band: When averaging only the events following single pulse stimulation (SaS; ), a synchronization pattern emerges ~ 200 ms after stimulus onset and continues up to > 300 ms (similar to what we have initially expected based on our previous studies; ; ), whereas trials following subthreshold train stimulation (SaT; ) are associated with a poststimulus desynchronization from ~ 250 to > 300 ms.

Techniques: Comparison

Journal: Cerebral Cortex (New York, NY)

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

doi: 10.1093/cercor/bhaa185

Figure Lengend Snippet: SEPs. ( A ) Grand average SEPs (40 subjects) in response to single pulse stimulation on the left index finger. Left: subthreshold (red) SEP confirming the characteristic P60 component; suprathreshold SEP (green). Right: SEPs for subthreshold stimulation sorted according pre-trial history (SaS and SaT; dark and light gray, respectively), both comprising a P60 component (no significant difference). Below: topographic maps of the P50 and P60 component for supra- and subthreshold single pulse stimulation, respectively. ( B ) Grand average (blue) for subthreshold train stimulation with presumable initial pulse-related component but lacking consecutive train-driven synchronicity (dotted red: single pulse-SEP shown in drawn repetitively as a ‘‘pseudo-phase-locked’’ response to each pulse of the train for comparison); bottom right: grand average SEPs for subthreshold train stimulation (initial part) sorted according to pre-trial history (train, TaS, and TaT; blue, dark, and light gray, respectively); bottom left: topographic map of the initial P60 component in response to subthreshold train stimulation.

Article Snippet: When sorting the single pulse time-frequency analyses (TFAs) according to the past trial, we observe differential changes in the alpha frequency band: When averaging only the events following single pulse stimulation (SaS; ), a synchronization pattern emerges ~ 200 ms after stimulus onset and continues up to > 300 ms (similar to what we have initially expected based on our previous studies; ; ), whereas trials following subthreshold train stimulation (SaT; ) are associated with a poststimulus desynchronization from ~ 250 to > 300 ms.

Techniques: Comparison

Journal: Cerebral Cortex (New York, NY)

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

doi: 10.1093/cercor/bhaa185

Figure Lengend Snippet: Psychophysical performance. Detection rates obtained in six separate experiments (A1 to A3 and B1 to B3; as described in ). Upper panel: Subthreshold single pulse stimulation was associated with an increase of mean detection rate by 6.5% (relative change, i.e., as compared to the target only condition) for a delay of 60 ms between near-threshold TP and preceding subthreshold single pulse; for the other delays (30 and 180 ms), no significant change was found. Lower panel: Subthreshold pulse train stimulation induced a significant decrease in mean TP detection rates for all tested delays, by 5.0%, 3.9%, and 7.7% (relative changes) for a delay of 30, 60 (after the fifth pulse of the train, respectively), and 180 ms (after end of the train).

Article Snippet: When sorting the single pulse time-frequency analyses (TFAs) according to the past trial, we observe differential changes in the alpha frequency band: When averaging only the events following single pulse stimulation (SaS; ), a synchronization pattern emerges ~ 200 ms after stimulus onset and continues up to > 300 ms (similar to what we have initially expected based on our previous studies; ; ), whereas trials following subthreshold train stimulation (SaT; ) are associated with a poststimulus desynchronization from ~ 250 to > 300 ms.

Techniques: