Brain State-dependent Gain Modulation of Corticospinal Output in the Active Motor System

2019 ◽  
Vol 30 (1) ◽  
pp. 371-381 ◽  
Author(s):  
Georgios Naros ◽  
Tobias Lehnertz ◽  
Maria Teresa Leão ◽  
Ulf Ziemann ◽  
Alireza Gharabaghi
Keyword(s):  
Muscle Activation ◽  
Motor Evoked Potentials ◽  
Brain State ◽  
Robotic Hand ◽  
Response Modulation ◽  
Beta Band ◽  
State Dependent ◽  
Communication Through Coherence ◽  
Oscillatory Cycle ◽  
Hand Opening

Abstract The communication through coherence hypothesis suggests that only coherently oscillating neuronal groups can interact effectively and predicts an intrinsic response modulation along the oscillatory rhythm. For the motor cortex (MC) at rest, the oscillatory cycle has been shown to determine the brain’s responsiveness to external stimuli. For the active MC, however, the demonstration of such a phase-specific modulation of corticospinal excitability (CSE) along the rhythm cycle is still missing. Motor evoked potentials in response to transcranial magnetic stimulation (TMS) over the MC were used to probe the effect of cortical oscillations on CSE during several motor conditions. A brain–machine interface (BMI) with a robotic hand orthosis allowed investigating effects of cortical activity on CSE without the confounding effects of voluntary muscle activation. Only this BMI approach (and not active or passive hand opening alone) revealed a frequency- and phase-specific cortical modulation of CSE by sensorimotor beta-band activity that peaked once per oscillatory cycle and was independent of muscle activity. The active MC follows an intrinsic response modulation in accordance with the communication through coherence hypothesis. Furthermore, the BMI approach may facilitate and strengthen effective corticospinal communication in a therapeutic context, for example, when voluntary hand opening is no longer possible after stroke.

scholarly journals EEG-triggered TMS reveals stronger brain state-dependent modulation of motor evoked potentials at weaker stimulation intensities

2019 ◽  
Vol 12 (1) ◽  
pp. 110-118 ◽  
Author(s):  
Natalie Schaworonkow ◽  
Jochen Triesch ◽  
Ulf Ziemann ◽  
Christoph Zrenner
Keyword(s):  
Evoked Potentials ◽  
Motor Evoked Potentials ◽  
Brain State ◽  
State Dependent

scholarly journals Decoding individualized motor cortical excitability states from whole-brain electroencephalography

2021 ◽  
Author(s):  
Sara J Hussain ◽  
Romain Quentin
Keyword(s):  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Brain State ◽  
Individual Subject ◽  
Whole Brain ◽  
State Dependent ◽  
Subject Specific ◽  
The Individual ◽  
Real Time Identification ◽  
The Right

OBJECTIVE: Brain state-dependent transcranial magnetic stimulation (TMS) requires real-time identification of cortical excitability states. Here, we aimed to identify individualized, subject-specific motor cortex (M1) excitability states from whole-scalp electroencephalography (EEG) signals. METHODS: We analyzed a pre-existing dataset that delivered 600 single TMS pulses to the right M1 during EEG and electromyography (EMG) recordings. Subject-specific multivariate pattern classification was used to discriminate between brain states during which TMS elicited small or large motor-evoked potentials (MEPs). RESULTS: Classifiers trained at the individual subject level successfully discriminated between low and high M1 excitability states. MEPs elicited during classifier-predicted high excitability states were significantly larger than those elicited during classifier-predicted low excitability states. Classifiers trained on subject-specific data obtained immediately before TMS delivery performed better than classifiers trained on data from earlier time points, and subject-specific classifiers generalized weakly but significantly across subjects. CONCLUSION: Decoding individualized M1 excitability states from whole-brain EEG activity is feasible and robust. SIGNIFICANCE: Deploying subject-specific classifiers during brain state-dependent TMS may enable effective, fully individualized neuromodulation in the future.

scholarly journals EEG-triggered TMS reveals stronger brain state-dependent modulation of motor evoked potentials at weaker stimulation intensities

2018 ◽  
Author(s):  
Natalie Schaworonkow ◽  
Jochen Triesch ◽  
Ulf Ziemann ◽  
Christoph Zrenner
Keyword(s):  
Evoked Potentials ◽  
Real Time ◽  
Motor Evoked Potentials ◽  
Corticospinal Excitability ◽  
Brain State ◽  
Stimulation Intensity ◽  
Negative Peak ◽  
State Dependent ◽  
Wide Range ◽  
Brain States

AbstractBackgroundCorticospinal excitability depends on the current brain state. The recent development of real-time EEG-triggered transcranial magnetic stimulation (EEG-TMS) allows studying this relationship in a causal fashion. Specifically, it has been shown that corticospinal excitability is higher during the scalp surface negative EEG peak compared to the positive peak of µ-oscillations in sensorimotor cortex, as indexed by larger motor evoked potentials (MEPs) for fixed stimulation intensity.ObjectiveWe further characterize the effect of µ-rhythm phase on the MEP input-output (IO) curve by measuring the degree of excitability modulation across a range of stimulation intensities. We furthermore seek to optimize stimulation parameters to enable discrimination of functionally relevant EEG-defined brain states.MethodsA real-time EEG-TMS system was used to trigger MEPs during instantaneous brain-states corresponding to µ-rhythm surface positive and negative peaks with five different stimulation intensities covering an individually calibrated MEP IO curve in 15 healthy participants.ResultsMEP amplitude is modulated by µ-phase across a wide range of stimulation intensities, with larger MEPs at the surface negative peak. The largest relative MEP-modulation was observed for weak intensities, the largest absolute MEP-modulation for intermediate intensities. These results indicate a leftward shift of the MEP IO curve during the µ-rhythm negative peak.ConclusionThe choice of stimulation intensity influences the observed degree of corticospinal excitability modulation by µ-phase. Lower stimulation intensities enable more efficient differentiation of EEG µ-phase-defined brain states.

scholarly journals An Analysis of the External Validity of EEG Spectral Power in an Uncontrolled Outdoor Environment during Default and Complex Neurocognitive States

2021 ◽  
Vol 11 (3) ◽  
pp. 330
Author(s):  
Dalton J. Edwards ◽  
Logan T. Trujillo
Keyword(s):  
External Validity ◽  
Spectral Power ◽  
Brain Activity ◽  
Outdoor Environment ◽  
Oscillatory Activity ◽  
Brain State ◽  
Beta Band ◽  
Eeg Spectral Power ◽  
Eeg Power ◽  
Human Participants

Traditionally, quantitative electroencephalography (QEEG) studies collect data within controlled laboratory environments that limit the external validity of scientific conclusions. To probe these validity limits, we used a mobile EEG system to record electrophysiological signals from human participants while they were located within a controlled laboratory environment and an uncontrolled outdoor environment exhibiting several moderate background influences. Participants performed two tasks during these recordings, one engaging brain activity related to several complex cognitive functions (number sense, attention, memory, executive function) and the other engaging two default brain states. We computed EEG spectral power over three frequency bands (theta: 4–7 Hz, alpha: 8–13 Hz, low beta: 14–20 Hz) where EEG oscillatory activity is known to correlate with the neurocognitive states engaged by these tasks. Null hypothesis significance testing yielded significant EEG power effects typical of the neurocognitive states engaged by each task, but only a beta-band power difference between the two background recording environments during the default brain state. Bayesian analysis showed that the remaining environment null effects were unlikely to reflect measurement insensitivities. This overall pattern of results supports the external validity of laboratory EEG power findings for complex and default neurocognitive states engaged within moderately uncontrolled environments.

scholarly journals Central excitability does not limit postfatigue voluntary activation of quadriceps femoris

2006 ◽  
Vol 100 (6) ◽  
pp. 1757-1764 ◽  
Author(s):  
J. M. Kalmar ◽  
E. Cafarelli
Keyword(s):  
Evoked Potentials ◽  
Repeated Measures ◽  
Muscle Activation ◽  
Motor Evoked Potentials ◽  
Vastus Lateralis ◽  
Central Fatigue ◽  
Knee Extension ◽  
Voluntary Activation ◽  
Fatigue Protocol ◽  
Central Excitability

After fatigue, motor evoked potentials (MEP) elicited by transcranial magnetic stimulation and cervicomedullary evoked potentials elicited by stimulation of the corticospinal tract are depressed. These reductions in corticomotor excitability and corticospinal transmission are accompanied by voluntary activation failure, but this may not reflect a causal relationship. Our purpose was to determine whether a decline in central excitability contributes to central fatigue. We hypothesized that, if central excitability limits voluntary activation, then a caffeine-induced increase in central excitability should offset voluntary activation failure. In this repeated-measures study, eight men each attended two sessions. Baseline measures of knee extension torque, maximal voluntary activation, peripheral transmission, contractile properties, and central excitability were made before administration of caffeine (6 mg/kg) or placebo. The amplitude of vastus lateralis MEPs elicited during minimal muscle activation provided a measure of central excitability. After a 1-h rest, baseline measures were repeated before, during, and after a fatigue protocol that ended when maximal voluntary torque declined by 35% (Tlim). Increased prefatigue MEP amplitude ( P = 0.055) and cortically evoked twitch ( P < 0.05) in the caffeine trial indicate that the drug increased central excitability. In the caffeine trial, increased MEP amplitude was correlated with time to task failure ( r = 0.74, P < 0.05). Caffeine potentiated the MEP early in the fatigue protocol ( P < 0.05) and offset the 40% decline in placebo MEP ( P < 0.05) at Tlim. However, this was not associated with enhanced maximal voluntary activation during fatigue or recovery, demonstrating that voluntary activation is not limited by central excitability.

scholarly journals Brain state-dependent stimulation boosts functional recovery following stroke

2018 ◽  
Vol 85 (1) ◽  
pp. 84-95 ◽  
Author(s):  
Natalie Mrachacz-Kersting ◽  
Andrew J. T. Stevenson ◽  
Helle R. M. Jørgensen ◽  
Kåre Eg Severinsen ◽  
Susan Aliakbaryhosseinabadi ◽  
...  
Keyword(s):  
Functional Recovery ◽  
Brain State ◽  
State Dependent

scholarly journals Corticospinal excitability of the biceps brachii is shoulder position dependent

2017 ◽  
Vol 118 (6) ◽  
pp. 3242-3251 ◽  
Author(s):  
Brandon Wayne Collins ◽  
Edward W. J. Cadigan ◽  
Lucas Stefanelli ◽  
Duane C. Button
Keyword(s):  
Evoked Potentials ◽  
Maximal Voluntary Contraction ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
Voluntary Contraction ◽  
Corticospinal Excitability ◽  
State Dependent ◽  
Shoulder Flexion ◽  
Erb’S Point ◽  
Shoulder Position

The purpose of this study was to examine the effect of shoulder position on corticospinal excitability (CSE) of the biceps brachii during rest and a 10% maximal voluntary contraction (MVC). Participants ( n = 9) completed two experimental sessions with four conditions: 1) rest, 0° shoulder flexion; 2) 10% MVC, 0° shoulder flexion; 3) rest, 90° shoulder flexion; and 4) 10% MVC, 90° shoulder flexion. Transcranial magnetic, transmastoid electrical, and Erb’s point stimulation were used to induce motor-evoked potentials (MEPs), cervicomedullary MEPs (CMEPs), and maximal muscle compound potentials (Mmax), respectively, in the biceps brachii in each condition. At rest, MEP, CMEP, and Mmax amplitudes increased ( P < 0.01) by 509.7 ± 118.3%, 113.3 ± 28.3%, and 155.1 ± 47.9%, respectively, at 90° compared with 0°. At 10% MVC, MEP amplitudes did not differ ( P = 0.08), but CMEP and Mmax amplitudes increased ( P < 0.05) by 32.3 ± 10.5% and 127.9 ± 26.1%, respectively, at 90° compared with 0°. MEP/Mmax increased ( P < 0.01) by 224.0 ± 99.1% at rest and decreased ( P < 0.05) by 51.3 ± 6.7% at 10% MVC at 90° compared with 0°. CMEP/Mmax was not different ( P = 0.22) at rest but decreased ( P < 0.01) at 10% MVC by 33.6 ± 6.1% at 90° compared with 0°. EMG increased ( P < 0.001) by 8.3 ± 2.0% at rest and decreased ( P < 0.001) by 21.4 ± 4.4% at 10% MVC at 90° compared with 0°. In conclusion, CSE of the biceps brachii was dependent on shoulder position, and the pattern of change was altered within the state in which it was measured. The position-dependent changes in Mmax amplitude, EMG, and CSE itself all contribute to the overall change in CSE of the biceps brachii. NEW & NOTEWORTHY We demonstrate that when the shoulder is placed into two common positions for determining elbow flexor force and activation, corticospinal excitability (CSE) of the biceps brachii is both shoulder position and state dependent. At rest, when the shoulder is flexed from 0° to 90°, supraspinal factors predominantly alter CSE, whereas during a slight contraction, spinal factors predominantly alter CSE. Finally, the normalization techniques frequently used by researchers to investigate CSE may under- and overestimate CSE when shoulder position is changed.

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