Time-varying coupling of EEG oscillations predicts excitability fluctuations in the primary motor cortex as reflected by motor evoked potentials amplitude: An EEG-TMS study

✓ The feasibility of high-frequency transcranial electrical stimulation (TES) through screw electrodes placed in the skull was investigated for use in intraoperative monitoring of the motor pathways in patients who are in a state of general anesthesia during cerebral and spinal operations. Motor evoked potentials (MEPs) were elicited by TES with a train of five square-wave pulses (duration 400 µsec, intensity ≤ 200 mA, frequency 500 Hz) delivered through metal screw electrodes placed in the outer table of the skull over the primary motor cortex in 42 patients. Myogenic MEPs to anodal stimulation were recorded from the abductor pollicis brevis (APB) and tibialis anterior (TA) muscles. The mean threshold stimulation intensity was 48 ± 17 mA for the APB muscles, and 112 ± 35 mA for the TA muscles. The electrodes were firmly fixed at the site and were not dislodged by surgical manipulation throughout the operation. No adverse reactions attributable to the TES were observed. Passing current through the screw electrodes stimulates the motor cortex more effectively than conventional methods of TES. The method is safe and inexpensive, and it is convenient for intraoperative monitoring of motor pathways.

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The Excitability of Ipsilateral Motor Evoked Potentials Is Not Task-specific and Spatially Distinct From the Contralateral Motor Hotspot

10.21203/rs.3.rs-1174677/v1 ◽

2022 ◽

Author(s):

Nelly Seusing ◽

Sebastian Strauss ◽

Robert Fleischmann ◽

Christina Nafz ◽

Sergiu Groppa ◽

...

Keyword(s):

Motor Cortex ◽

Evoked Potentials ◽

Primary Motor Cortex ◽

Biceps Brachii ◽

Motor Evoked Potentials ◽

Elbow Flexion ◽

Motor Pathways ◽

Task Dependence ◽

Flexion Extension ◽

Voluntary Contractions

Abstract ObjectiveThe role of ipsilateral descending motor pathways in voluntary movement of humans is still a matter of debate. Few studies have examined the task dependent modulation of ipsilateral motor evoked potentials (iMEPs). Here, we determined the location of upper limb biceps brachii (BB) representation within the ipsilateral primary motor cortex. MethodsMR-navigated transcranial magnetic stimulation mapping of the dominant hemisphere was undertaken with twenty healthy participants who made tonic unilateral, bilateral homologous or bilateral antagonistic elbow flexion-extension voluntary contractions. Map center of gravity (CoG) and area for each BB were obtained. ResultsThe map CoG of the ipsilateral BB was located more anterior-laterally than those of the contralateral BB within the primary motor cortex. However different tasks had no effect on either the iMEP CoG location or the size. ConclusionOur data suggests that ipsilateral and contralateral MEP might originate in distinct adjacent neural populations in the primary motor cortex, independent of task dependence.

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Local Differences in Cortical Excitability – A Systematic Mapping Study of the TMS-Evoked N100 Component

Frontiers in Neuroscience ◽

10.3389/fnins.2021.623692 ◽

2021 ◽

Vol 15 ◽

Author(s):

Daniela Roos ◽

Lea Biermann ◽

Tomasz A. Jarczok ◽

Stephan Bender

Keyword(s):

Motor Cortex ◽

Evoked Potentials ◽

Primary Motor Cortex ◽

Cortical Excitability ◽

Motor Evoked Potentials ◽

Hot Spot ◽

Source Analysis ◽

Systematic Mapping Study ◽

Stimulation Site ◽

Two Parameters

Transcranial magnetic stimulation (TMS) with simultaneous electroencephalography applied to the primary motor cortex provides two parameters for cortical excitability: motor evoked potentials (MEPs) and TMS-evoked potentials (TEPs). This study aimed to evaluate the effects of systematic coil shifts on both the TEP N100 component and MEPs in addition to the relationship between both parameters. In 12 healthy adults, the center of a standardized grid was fixed above the hot spot of the target muscle of the left primary motor cortex. Twelve additional positions were arranged in a quadratic grid with positions between 5 and 10 mm from the hot spot. At each of the 13 positions, TMS single pulses were applied. The topographical maximum of the resulting N100 was located ipsilateral and slightly posterior to the stimulation site. A source analysis revealed an equivalent dipole localized more deeply than standard motor cortex coordinates that could not be explained by a single seeded primary motor cortex dipole. The N100 topography might not only reflect primary motor cortex activation, but also sum activation of the surrounding cortex. N100 amplitude and latency decreased significantly during stimulation anterior-medial to the hot spot although MEP amplitudes were smaller at all other stimulation sites. Therefore, N100 amplitudes might be suitable for detecting differences in local cortical excitability. The N100 topography, with its maximum located posterior to the stimulation site, possibly depends on both anatomical characteristics of the stimulated cortex and differences in local excitability of surrounding cortical areas. The less excitable anterior cortex might contribute to a more posterior maximum. There was no correlation between N100 and MEP amplitudes, but a single-trial analysis revealed a trend toward larger N100 amplitudes in trials with larger MEPs. Thus, functionally efficient cortical excitation might increase the probability of higher N100 amplitudes, but TEPs are also generated in the absence of MEPs.

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The latency of motor-evoked potentials (MEPs) can predict whether cTBS will exert an inhibitory or excitatory effect on the ipsilateral and contralateral primary motor cortex

Frontiers in Human Neuroscience ◽

10.3389/conf.fnhum.2014.214.00080 ◽

2014 ◽

Vol 8 ◽

Author(s):

Huang Gan ◽

Mouraux André

Keyword(s):

Motor Cortex ◽

Evoked Potentials ◽

Primary Motor Cortex ◽

Motor Evoked Potentials ◽

Excitatory Effect

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Effects of coil orientation on Motor Evoked Potentials from Orbicularis Oris and First Dorsal Interosseous

10.1101/262261 ◽

2018 ◽

Author(s):

Patti Adank ◽

Dan Kennedy-Higgins ◽

Gwijde Maegherman ◽

Ricci Hannah ◽

Helen Nuttall

Keyword(s):

Motor Cortex ◽

Evoked Potentials ◽

Primary Motor Cortex ◽

Current Flow ◽

Motor Evoked Potentials ◽

First Dorsal Interosseous ◽

Left Hand ◽

Direct Activation ◽

Facial Muscles ◽

Posterior Anterior

AbstractObjectiveThis study aimed to characterise effects of coil orientation on the size of Motor Evoked Potentials (MEPs) from both sides of Orbicularis Oris (OO) and compare these effects with those reported for First Dorsal Interosseous (FDI), following stimulation to left lip and left hand Primary Motor Cortex.MethodsUsing a 70 mm figure-of-eight coil, we collected MEPs from eight different orientations while recording from contralateral and ipsilateral OO and FDI using a monophasic pulse.ResultsMEPs from OO were evoked consistently for six out of eight orientations for contralateral and ipsilateral sites. When latency and silent periods were taken into account, contralateral orientations 0°, 45°, 90°, and 315° were found to best elicit OO MEPs with a likely cortical origin. As expected, the largest FDI MEPs were recorded with an orientation of 45°, invoking a posterior-anterior (PA) current flow, from the contralateral location.ConclusionOrientations traditionally used for FDI were also found suitable for eliciting OO MEPs. Individuals vary more in their optimal coil orientation for eliciting MEPs from OO than for FDI. It is recommended that researchers iteratively probe several orientations when eliciting MEPs from OO. Care must be taken however because several orientations likely induced direct activation of facial muscles.

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Influence of iTBS on the Acute Neuroplastic Change After BCI Training

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2021.653487 ◽

2021 ◽

Vol 15 ◽

Author(s):

Qian Ding ◽

Tuo Lin ◽

Manfeng Wu ◽

Wenqing Yang ◽

Wanqi Li ◽

...

Keyword(s):

Prefrontal Cortex ◽

Functional Connectivity ◽

Motor Cortex ◽

Evoked Potentials ◽

Primary Motor Cortex ◽

Motor Evoked Potentials ◽

Silent Period ◽

Single Pulse ◽

Functional Near Infrared Spectroscopy ◽

Significant Difference

Objective: Brain-computer interface (BCI) training is becoming increasingly popular in neurorehabilitation. However, around one third subjects have difficulties in controlling BCI devices effectively, which limits the application of BCI training. Furthermore, the effectiveness of BCI training is not satisfactory in stroke rehabilitation. Intermittent theta burst stimulation (iTBS) is a powerful neural modulatory approach with strong facilitatory effects. Here, we investigated whether iTBS would improve BCI accuracy and boost the neuroplastic changes induced by BCI training.Methods: Eight right-handed healthy subjects (four males, age: 20–24) participated in this two-session study (BCI-only session and iTBS+BCI session in random order). Neuroplastic changes were measured by functional near-infrared spectroscopy (fNIRS) and single-pulse transcranial magnetic stimulation (TMS). In BCI-only session, fNIRS was measured at baseline and immediately after BCI training. In iTBS+BCI session, BCI training was followed by iTBS delivered on the right primary motor cortex (M1). Single-pulse TMS was measured at baseline and immediately after iTBS. fNIRS was measured at baseline, immediately after iTBS, and immediately after BCI training. Paired-sample t-tests were used to compare amplitudes of motor-evoked potentials, cortical silent period duration, oxygenated hemoglobin (HbO2) concentration and functional connectivity across time points, and BCI accuracy between sessions.Results: No significant difference in BCI accuracy was detected between sessions (p > 0.05). In BCI-only session, functional connectivity matrices between motor cortex and prefrontal cortex were significantly increased after BCI training (p's < 0.05). In iTBS+BCI session, amplitudes of motor-evoked potentials were significantly increased after iTBS (p's < 0.05), but no change in HbO2 concentration or functional connectivity was observed throughout the whole session (p's > 0.05).Conclusions: To our knowledge, this is the first study that investigated how iTBS targeted on M1 influences BCI accuracy and the acute neuroplastic changes after BCI training. Our results revealed that iTBS targeted on M1 did not influence BCI accuracy or facilitate the neuroplastic changes after BCI training. Therefore, M1 might not be an effective stimulation target of iTBS for the purpose of improving BCI accuracy or facilitate its effectiveness; other brain regions (i.e., prefrontal cortex) are needed to be further investigated as potentially effective stimulation targets.

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The spectral features of EEG responses to transcranial magnetic stimulation of the primary motor cortex depend on the amplitude of the motor evoked potentials

10.1101/133769 ◽

2017 ◽

Author(s):

Matteo Fecchio ◽

Andrea Pigorini ◽

Angela Comanducci ◽

Simone Sarasso ◽

Silvia Casarotto ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Evoked Potentials ◽

Magnetic Stimulation ◽

Primary Motor Cortex ◽

Motor Evoked Potentials ◽

Spectral Features ◽

Time Frequency ◽

Resting Motor Threshold ◽

Wide Range

ABSTRACTTranscranial magnetic stimulation (TMS) of the primary motor cortex (M1) can excite both cortico-cortical and cortico-spinal axons resulting in TMS-evoked potentials (TEPs) and motor-evoked potentials (MEPs), respectively. Despite this remarkable difference with other cortical areas, the influence of motor output and its amplitude on TEPs is largely unknown. Here we studied TEPs resulting from M1 stimulation and assessed whether their waveform and spectral features depend on the MEP amplitude. To this aim, we performed two separate experiments. In experiment 1, single-pulse TMS was applied at the same supra-threshold intensity on primary motor, prefrontal, premotor and parietal cortices and the corresponding TEPs were compared by means of local mean field power and time-frequency spectral analysis. In experiment 2 we stimulated M1 at resting motor threshold in order to elicit MEPs characterized by a wide range of amplitudes. TEPs computed from high-MEP and low-MEP trials were then compared using the same methods applied in experiment 1. In line with previous studies, TMS of M1 produced larger TEPs compared to other cortical stimulations. Notably, we found that only TEPs produced by M1 stimulation were accompanied by a late (∼300 ms after TMS) event-related desynchronization (ERD), whose magnitude was strongly dependent on the amplitude of MEPs. Overall, these results suggest that M1 produces peculiar responses to TMS possibly reflecting specific anatomo-functional properties, such as the re-entry of proprioceptive feedback associated with target muscle activation.

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Cerebellar rTMS and PAS effectively induce cerebellar plasticity

Scientific Reports ◽

10.1038/s41598-021-82496-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Martje G. Pauly ◽

Annika Steinmeier ◽

Christina Bolte ◽

Feline Hamami ◽

Elinor Tzvi ◽

...

Keyword(s):

Motor Cortex ◽

Healthy Subjects ◽

Primary Motor Cortex ◽

Cortical Excitability ◽

Motor Evoked Potentials ◽

Repetitive Transcranial Magnetic Stimulation ◽

Premotor Cortex ◽

Motor Pathways ◽

Non Invasive ◽

Cerebellar Plasticity

AbstractNon-invasive brain stimulation techniques including repetitive transcranial magnetic stimulation (rTMS), continuous theta-burst stimulation (cTBS), paired associative stimulation (PAS), and transcranial direct current stimulation (tDCS) have been applied over the cerebellum to induce plasticity and gain insights into the interaction of the cerebellum with neo-cortical structures including the motor cortex. We compared the effects of 1 Hz rTMS, cTBS, PAS and tDCS given over the cerebellum on motor cortical excitability and interactions between the cerebellum and dorsal premotor cortex / primary motor cortex in two within subject designs in healthy controls. In experiment 1, rTMS, cTBS, PAS, and tDCS were applied over the cerebellum in 20 healthy subjects. In experiment 2, rTMS and PAS were compared to sham conditions in another group of 20 healthy subjects. In experiment 1, PAS reduced cortical excitability determined by motor evoked potentials (MEP) amplitudes, whereas rTMS increased motor thresholds and facilitated dorsal premotor-motor and cerebellum-motor cortex interactions. TDCS and cTBS had no significant effects. In experiment 2, MEP amplitudes increased after rTMS and motor thresholds following PAS. Analysis of all participants who received rTMS and PAS showed that MEP amplitudes were reduced after PAS and increased following rTMS. rTMS also caused facilitation of dorsal premotor-motor cortex and cerebellum-motor cortex interactions. In summary, cerebellar 1 Hz rTMS and PAS can effectively induce plasticity in cerebello-(premotor)-motor pathways provided larger samples are studied.

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