Persistent Elevation of Electrical Pain Threshold following Continuous Theta Burst Stimulation over Primary Somatosensory Cortex in Humans

Rao, Nishant; Chen, Yen‐Ting; Ramirez, Regan; Tran, John; Li, Sheng; Parikh, Pranav J.

doi:10.1101/724344

Cited by 2 publications

(2 citation statements)

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“…Time PFR , variability in humans. The rise in CSE variability was associated with Time PFR variability but not with variability in magnitude of peak force rate, although both factors are known to be important for accurate force application (Poston et al, 2008). It is plausible that the intertrial variability in CSE may encode the variability in timing of force application as a control variable.…”

Section: Rise In Cse Variability Explains Inter-individual Differencementioning

confidence: 90%

“…In presence of visual feedback, as in this study, peak force rate is also influenced by online adjustments of grip force. We analyzed magnitude and time to peak force rate (Time PFR ) to assess behavioral variability, as previously reported by Flanagan and Beltzner (2000) and Poston et al (2008). To compute the rate of grip force application, we first smoothed the grip force signal through a zero-phase lag, fourth order, low-pass Butterworth filter (cutoff frequency: 14 Hz) followed by calculating its first derivative with respect to the trial time (Flanagan and Beltzner, 2000).…”

Section: Behavioral Variability In the Application Of Forcementioning

confidence: 99%

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Fluctuations in Human Corticospinal Activity Prior to Grasp

Rao

Parikh

2019

Front. Syst. Neurosci.

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Neuronal firing rate variability prior to movement onset contributes to trial-to-trial variability in primate behavior. However, in humans, whether similar mechanisms contribute to trial-to-trial behavioral variability remains unknown. We investigated the time-course of trial-to-trial variability in corticospinal excitability (CSE) using transcranial magnetic stimulation (TMS) during a self-paced reach-to-grasp task. We hypothesized that CSE variability will be modulated prior to the initiation of reach and that such a modulation would explain trial-to-trial behavioral variability. Able-bodied individuals were visually cued to plan their grip force before exertion of either 30% or 5% of their maximum pinch force capacity on an object. TMS was delivered at six time points (0.5, 0.75, 1, 1.1, 1.2, and 1.3 s) following a visual cue that instructed the force level. We first modeled the relation between CSE magnitude and its variability at rest (n = 12) to study the component of CSE variability pertaining to the task but not related to changes in CSE magnitude (n = 12). We found an increase in CSE variability from 1.2 to 1.3 s following the visual cue at 30% but not at 5% of force. This effect was temporally dissociated from the decrease in CSE magnitude that was observed from 0.5 to 0.75 s following the cue. Importantly, the increase in CSE variability explained at least ∼40% of inter-individual differences in trial-to-trial variability in time to peak force rate. These results were found to be repeatable across studies and robust to different analysis methods. Our findings suggest that the neural mechanisms underlying modulation in CSE variability and CSE magnitude are distinct. Notably, the extent of modulation in variability in corticospinal system prior to grasp within individuals may explain their trial-to-trial behavioral variability.

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Section: Rise In Cse Variability Explains Inter-individual Differencementioning

confidence: 90%

Section: Behavioral Variability In the Application Of Forcementioning

confidence: 99%

Fluctuations in Human Corticospinal Activity Prior to Grasp

Rao

Parikh

2019

Front. Syst. Neurosci.

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Lateralized Neural Entropy modulates with Grip Force during Precision Grasping

Rao

Paek

Contreras-Vidal

et al. 2023

Preprint

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When holding a coffee mug filled to the brim, we strive to avoid spilling the coffee. This ability relies on the neural processes underlying the control of finger forces on a moment-to-moment basis. The brain activity lateralized to the contralateral hemisphere averaged over a trial and across the trials is known to be associated with the magnitude of grip force applied on an object. However, the mechanistic involvement of the variability in neural signals during grip force control remains unclear. In this study, we examined the dependence of neural variability over the frontal, central, and parietal regions assessed using noninvasive electroencephalography (EEG) on grip force magnitude during an isometric force control task. We hypothesized laterally specific modulation in EEG variability with higher magnitude of the grip force exerted during grip force control. We utilized an existing EEG dataset (64 channel) comprised of healthy young adults, who performed an isometric force control task while receiving visual feedback of the force applied. The force magnitude to be exerted on the instrumented object was cued to participants during the task, and varied pseudorandomly among 5, 10, and 15% of their maximum voluntary contraction (MVC) across the trials. We quantified neural variability via sample entropy (sequence-dependent measure) and standard deviation (sequence-independent measure) of the temporal EEG signal over the frontal, central, and parietal electrodes. The EEG sample entropy over the central electrodes showed lateralized, nonlinear, localized, modulation with force magnitude. Similar modulation was not observed over frontal or parietal EEG activity, nor for standard deviation in the EEG activity. Our findings highlight specificity in neural control of grip forces by demonstrating the modulation in sequence-dependent but not sequence-independent component of EEG variability. This modulation appeared to be lateralized, spatially constrained, and functionally dependent on the grip force magnitude. We discuss the relevance of these findings in scenarios where a finer precision is essential to enable grasp application, such as prosthesis and associated neural signal integration, and propose directions for future studies investigating the mechanistic role of neural entropy in grip force control.

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Persistent Elevation of Electrical Pain Threshold following Continuous Theta Burst Stimulation over Primary Somatosensory Cortex in Humans

Cited by 2 publications

References 48 publications

Fluctuations in Human Corticospinal Activity Prior to Grasp

Fluctuations in Human Corticospinal Activity Prior to Grasp

Lateralized Neural Entropy modulates with Grip Force during Precision Grasping

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