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Item type:Publication, Multimodal neuroimaging of fatigability development(MIT Press, 2025); Traian PopaFatigability refers to the inability of the neuromuscular system to generate enough force to produce movements to meet task challenges. Fatigability has a central and a peripheral component linked via the neuromuscular system, but how these two components interact as fatigue develops lacks a complete understanding. The effects of fatigability are experienced in healthy humans but also accompany various disorders, often exacerbating their symptoms. We studied how fatigability develops in the neuromuscular system using multimodal neuroimaging. We recruited healthy participants to perform a fatiguing grip force task, while recording force, electromyography of forearm muscles (EMG), electroencephalography (EEG), and functional magnetic resonance imaging (fMRI) in 30-second blocks of grip task alternating with 30 seconds of rest. The task entailed maintaining 50% of the maximum force. We combined EMG and EEG to compute corticomuscular coherence and combined EEG and fMRI to compute EEG-informed fMRI. We selected eight task blocks specific to each participant to represent how the neuromuscular system adapted from pre-fatigability to actual fatigability. Those included five blocks for pre-fatigability in which participants could generate enough force to match the required 50% of maximum force and three blocks when the force fell below that limit. Across blocks of the grip force task, we observed changes in the neuromuscular system that preceded grip force changes. We found that electromyography of arm muscles shifted from high to low frequency, EEG in the channel covering the contralateral sensorimotor area increased steadily up to the fifth block and then plateaued, and fMRI signal also increased in the cerebellum. Corticomuscular coherence increased within each of the 30-second blocks of the grip task. EEG-informed fMRI revealed areas of the brain that the traditional regression did not, including the bilateral sensorimotor cortex, temporal-parietal junction, and supplementary motor area. Thus, as fatigability developed, the neuromuscular system experienced changes earlier than the actual behavior. While we found evidence for fatigability of central and peripheral origins, peripheral fatigue seems to occur first.2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Patterns of brain activity in choice or instructed go and no-go tasks(Springer Science and Business Media LLC, 2025-02-21); Mark HallettThe goal of this study was to investigate the decision making process for choosing what movements to make. We used electroencephalography (EEG) to investigate patterns of the contingent negative variation (CNV) associated with free-choice decisions to move or abstain, comparing them to conditions where actions were commanded. Our primary hypothesis was that choice tasks would differ significantly from each other and exhibit EEG patterns akin to their command-driven counterparts after the decisions were made, at least, in the 50 ms block of time prior to movement. A secondary analysis evaluated post hoc comparisons of time, in 50 ms blocks, to understand the temporal development of the CNV for each condition. We also conducted an exploratory analysis of EEG event-related desynchronization (ERD) to identify patterns of brain activity associated with the decision-making process. This approach was taken due to the exploratory nature of our hypotheses concerning the spatial and temporal characteristics of EEG activity during these free-choice versus commanded tasks. We studied 12 right-handed healthy volunteers (7 women, mean age 53 years, range 39–73 years) with no prior history of neurological or major psychiatric illness. A CNV paradigm encompassing commanded and choice tasks was devised, with a 2500 ms interval between S1 and S2, while recording EEG and electromyography (EMG). S1 provided full information about the upcoming task, which was to be executed at the time of S2. We assessed CNV and explored whole scalp EEG activity, including both voltage as well as power in the alpha and beta frequency ranges. Clear and similar CNVs were observed for command and choice go tasks prior to the movements, contrasting with near-zero CNVs for the command and choice no-go tasks. Separation of CNVs for command go and no-go tasks occurred around 1600 ms post-S1, and choice CNVs separated about 2150 ms post-S1. Exploratory analysis revealed that beta power provided information about decision and preparation processes much earlier. The left dorsolateral prefrontal cortex (DLPFC) exhibited the initial sign of decision approximately 500 ms post-S1 for all tasks, with subsequent preparation for movement or restraint involving distinct activity in various brain regions. The localization of effects in the left DLPFC was determined by visual analysis of the informative electrode sites. The CNVs separate about 2 s after S1, and it appears that this process represents preparation for movement (or no movement). Exploration of the beta activity suggests an earlier decision process which leads eventually to subsequent task preparation and activation. Choice decisions lag slightly behind command decisions, with the CNV apparently reflecting motor implementation rather than the decision-making process. In a simple motor task with an exploratory analysis, both commanded and choice-based decisions are rapidly initiated in the left DLPFC. While the CNV distinguishes between go and no-go conditions, it primarily appears to signify preparation for implementation of the task following the earlier decision. Further controlled studies will be needed to confirm these results.Scopus© Citations 3 1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Global Perceptions and Utilization of Clinical Neurophysiology in Movement Disorders(2024)Scopus© Citations 6 4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome(2024)Scopus© Citations 116 3 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, How to Do an Electrophysiological Study of Myoclonus(2022); 1Scopus© Citations 6 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Electrophysiological Characterization of a <scp><i>MYH7</i></scp> Variant with Tremor Phenotype(2023); Scopus© Citations 2 1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Tremoroton, a new free online platform for tremor analysis(2020); Scopus© Citations 4 16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, BacAv, a new free online platform for clinical back-averaging(2020); Scopus© Citations 6 4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measuring conduction velocity distributions in peripheral nerves using neurophysiological techniques(2020); Scopus© Citations 7 1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The role of the inferior parietal lobule in writer’s cramp(2020)Scopus© Citations 33 1
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