scholarly journals The influence of somatosensory and auditory evoked potentials on concurrent transcranial-magnetic stimulation electroencephalography recordings

2021 ◽  
Author(s):  
Nahian S Chowdhury ◽  
Nigel C Rogasch ◽  
Alan Chiang ◽  
Samantha K Millard ◽  
Patrick Skippen ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Magnetic Stimulation ◽  
Auditory Evoked Potentials ◽  
Cortical Excitability ◽  
Auditory Stimulation ◽  
Somatosensory Stimulation ◽  
Linear Interaction ◽  
Sham Stimulation

Background: Transcranial magnetic stimulation (TMS) evoked potentials (TEPs) can be used to index cortical excitability. However, it remains unclear to what extent TEPs reflect somatosensory and auditory-evoked potentials which arise from the scalp sensation and click of the TMS coil, as opposed to transcranial stimulation of cortical circuits. Objectives: The present study had two aims; a) to determine the extent to which sensory potentials contaminate TEPs using a spatially matched sham condition, and b) to determine whether sensory potentials reflect auditory or somatosensory potentials alone, or a combination of the two. Methods: Twenty healthy participants received active or sham stimulation, with the latter consisting of the click of a sham coil combined with scalp electrical stimulation. Earplugs/headphones were used to suppress the TMS click noise. Two additional control conditions i) electrical stimulation alone and ii) auditory stimulation alone were included in a subset of 13 participants. Results: Signals from active and sham stimulation were correlated in spatial and temporal domains, especially >70ms post-stimulation. Relative to auditory or electrical stimulation alone, combined (sham) stimulation resulted in a) larger evoked responses b) stronger correlations with active stimulation and c) a signal that could not be explained by the linear sum of electrical and auditory stimulation alone. Conclusions: Sensory potentials can confound data interpretations of TEPs at timepoints >70ms post-TMS, while earlier timepoints appear reflective of cortical excitability. Furthermore, contamination of TEPs cannot be explained by auditory or somatosensory potentials alone, but instead reflects a non-linear interaction between both sources. Future studies may benefit from controlling for sensory contamination using sham conditions that are spatially matched to active TMS, and which consist of combined auditory and somatosensory stimulation.

scholarly journals Modulation of motor cortical excitability with auditory stimulation

2018 ◽  
Vol 120 (3) ◽  
pp. 920-925
Author(s):  
Olli Löfberg ◽  
Petro Julkunen ◽  
Elisa Kallioniemi ◽  
Ari Pääkkönen ◽  
Jari Karhu
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Evoked Potentials ◽  
Magnetic Stimulation ◽  
Auditory Evoked Potentials ◽  
Cortical Excitability ◽  
Motor Cortical Excitability ◽  
Motor Cortex Excitability ◽  
Motor Cortical ◽  
Arousal Reaction

Loud sounds have been demonstrated to increase motor cortex excitability when transcranial magnetic stimulation (TMS) is synchronized with auditory evoked N100 potential measured from electroencephalography (EEG). The N100 potential is generated by an afferent response to sound onset and feature analysis, and upon novel sound it is also related to the arousal reaction. The arousal reaction is known to originate from the ascending reticular activating system of the brain stem and to modulate neuronal activity throughout the central nervous system. In this study we investigated the difference in motor evoked potentials (MEPs) when deviant and novelty stimuli were randomly interspersed in a train of standard tones. Twelve healthy subjects participated in this study. Three types of sound stimuli were used: 1) standard stimuli (800 Hz), 2) deviant stimuli (560 Hz), and 3) novelty stimuli (12 different sounds). In each stimulus sequence 600 stimuli were given. Of these, 90 were deviant stimuli randomly placed between the standard stimuli. Each of 12 novel sounds was presented once in pseudorandomized order. TMS was randomly mixed with the sound stimuli so that it was either synchronized with the individual N100 or trailed the sound onset by 200 ms. All sounds elicited an increase in motor cortex excitability. The type of sound had no significant effect. We also demonstrated that TMS timed at 200-ms intervals caused a significant increment of MEPs. This contradicted our hypothesis that MEP amplitudes to TMS synchronized with N100 would be greater than those to TMS at 200 ms after a sound and remains unexplained. NEW & NOTEWORTHY We demonstrated modulation of motor cortical excitability with parallel auditory stimulus by combining navigated transcranial magnetic stimulation (TMS) with auditory stimuli. TMS was synchronized with auditory evoked potentials considered to be generated by the unconscious attention call process in the auditory system.

Low-intensity repetitive transcranial magnetic stimulation decreases motor cortical excitability in humans

2006 ◽  
Vol 101 (2) ◽  
pp. 500-505 ◽  
Author(s):  
Gabrielle Todd ◽  
Stanley C. Flavel ◽  
Michael C. Ridding
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Motor Threshold ◽  
Sham Stimulation ◽  
Motor Cortical Excitability ◽  
Resting Motor Threshold ◽  
Active Motor ◽  
Motor Cortical

Repetitive transcranial magnetic stimulation of the motor cortex (rTMS) can be used to modify motor cortical excitability in human subjects. At stimulus intensities near to or above resting motor threshold, low-frequency rTMS (∼1 Hz) decreases motor cortical excitability, whereas high-frequency rTMS (5–20 Hz) can increase excitability. We investigated the effect of 10 min of intermittent rTMS on motor cortical excitability in normal subjects at two frequencies (2 or 6 Hz). Three low intensities of stimulation (70, 80, and 90% of active motor threshold) and sham stimulation were used. The number of stimuli were matched between conditions. Motor cortical excitability was investigated by measurement of the motor-evoked potential (MEP) evoked by single magnetic stimuli in the relaxed first dorsal interosseus muscle. The intensity of the single stimuli was set to evoke baseline MEPs of ∼1 mV in amplitude. Both 2- and 6-Hz stimulation, at 80% of active motor threshold, reduced the magnitude of MEPs for ∼30 min ( P < 0.05). MEPs returned to baseline values after a weak voluntary contraction. Stimulation at 70 and 90% of active motor threshold and sham stimulation did not induce a significant group effect on MEP magnitude. However, the intersubject response to rTMS at 90% of active motor threshold was highly variable, with some subjects showing significant MEP facilitation and others inhibition. These results suggest that, at low stimulus intensities, the intensity of stimulation may be as important as frequency in determining the effect of rTMS on motor cortical excitability.

An Increase in Cortical Excitability with No Change in Spinal Excitability during Motor Imagery

1996 ◽  
Vol 83 (1) ◽  
pp. 288-290 ◽  
Author(s):  
Susumu Yahagi ◽  
Kuniyoshi Shimura ◽  
Tatsuya Kasai
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Motor Imagery ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Emg Activity ◽  
Electrical Stimuli ◽  
Spinal Excitability ◽  
Flexor Carpi Radialis Muscle

During motor imagery, to estimate changes in excitability of flexor carpi radialis muscle motoneurons of the spinal and cortical levels, electrical stimuli for recording H-reflex and transcranial magnetic stimulation (TMS) for recording motor evoked potentials (MEPs) were used. In the absence of movement or detectable EMG activity during motor magery, there was an increase in cortical excitability with no change in spinal excitability

Repetitive transcranial magnetic stimulation on the modulation of cortical and spinal cord excitability in individuals with spinal cord injury

2021 ◽  
pp. 1-11
Author(s):  
Thyciane Mendonça ◽  
Rodrigo Brito ◽  
Plínio Luna ◽  
Mayara Campêlo ◽  
Lívia Shirahige ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Sham Stimulation ◽  
Resting Motor Threshold ◽  
Cord Injury ◽  
Spinal Excitability

Background: Repetitive transcranial magnetic stimulation (rTMS) has been applied for modulating cortical excitability and treating spasticity in neurological lesions. However, it is unclear which rTMS frequency is most effective in modulating cortical and spinal excitability in incomplete spinal cord injury (SCI). Objective: To evaluate electrophysiological and clinical repercussions of rTMS compared to sham stimulation when applied to the primary motor cortex (M1) in individuals with incomplete SCI. Methods: A total of 11 subjects (35±12 years) underwent three experimental sessions of rTMS (10 Hz, 1 Hz and sham stimulation) in a randomized order at 90%intensity of the resting motor threshold and interspersed by a seven-day interval between sessions. The following outcome measures were evaluated: M1 and spinal cord excitability and spasticity in the moments before (baseline), immediately after (T0), 30 (T30) and 60 (T60) minutes after rTMS. M1 excitability was obtained through the motor evoked potential (MEP); spinal cord excitability by the Hoffman reflex (H-reflex) and homosynaptic depression (HD); and spasticity by the modified Ashworth scale (MAS). Results: A significant increase in cortical excitability was observed in subjects submitted to 10 Hz rTMS at the T0 moment when compared to sham stimulation (p = 0.008); this increase was also significant at T0 (p = 0.009), T30 (p = 0.005) and T60 (p = 0.005) moments when compared to the baseline condition. No significant differences were observed after the 10 Hz rTMS on spinal excitability or on spasticity. No inter-group differences were detected, or in the time after application of 1 Hz rTMS, or after sham stimulation for any of the assessed outcomes. Conclusions: High-frequency rTMS applied to M1 was able to promote increased cortical excitability in individuals with incomplete SCI for at least 60 minutes; however, it did not modify spinal excitability or spasticity.

scholarly journals The correspondence between EMG and EEG measures of changes in cortical excitability following transcranial magnetic stimulation

2019 ◽  
Author(s):  
Mana Biabani ◽  
Alex Fornito ◽  
James P. Coxon ◽  
Ben D. Fulcher ◽  
Nigel C. Rogasch
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Evoked Potentials ◽  
High Frequency ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Single Pulse ◽  
Cortical Response ◽  
Response Component ◽  
Paired Pulse

AbstractTranscranial magnetic stimulation (TMS) is a powerful tool to investigate cortical circuits. Changes in cortical excitability following TMS are typically assessed by measuring changes in either conditioned motor-evoked potentials (MEPs) following paired-pulse TMS over motor cortex or evoked potentials measured with electroencephalography following single-pulse TMS (TEPs). However, it is unclear whether these two measures of cortical excitability index the same cortical response. Twenty-four healthy participants received local and interhemispheric paired-pulse TMS over motor cortex with eight inter-pulse intervals, suband suprathreshold conditioning intensities, and two different pulse waveforms, while MEPs were recorded from a hand muscle. TEPs were also recorded in response to single-pulse TMS using the conditioning pulse alone. The relationships between TEPs and conditioned-MEPs were evaluated using metrics sensitive to both their magnitude at each timepoint and their overall shape across time. The impacts of undesired sensory potentials resulting from TMS pulse and muscle contractions were also assessed on both measures. Both conditioned-MEPs and TEPs were sensitive to re-afferent somatosensory activity following motor-evoked responses, but over different post-stimulus timepoints. Moreover, the amplitude of low-frequency oscillations in TEPs was strongly correlated with the sensory potentials, whereas early and local high-frequency responses showed minimal relationships. Accordingly, conditioned-MEPs did not correlate with TEPs in the time domain but showed high shape similarity with the amplitude of high-frequency oscillations in TEPs. Therefore, despite the effects of sensory confounds, the TEP and MEP measures share a response component, suggesting that they index a similar cortical response and perhaps the same neuronal populations.

Induction of Long-Lasting Changes of Visual Cortex Excitability by Five Daily Sessions of Repetitive Transcranial Magnetic Stimulation (rTMS) in Healthy Volunteers and Migraine Patients

Cephalalgia ◽  
2006 ◽  
Vol 26 (2) ◽  
pp. 143-149 ◽  
Author(s):  
A Fumal ◽  
G Coppola ◽  
V Bohotin ◽  
P-Y Gérardy ◽  
L Seidel ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Healthy Volunteers ◽  
Visual Evoked Potentials ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Migraine Therapy ◽  
Visual Evoked

We have shown that in healthy volunteers (HV) one session of 1 Hz repetitive transcranial magnetic stimulation (rTMS) over the visual cortex induces dishabituation of visual evoked potentials (VEPs) on average for 30 min, while in migraineurs one session of 10 Hz rTMS replaces the abnormal VEP potentiation by a normal habituation for 9 min. In the present study, we investigated whether repeated rTMS sessions (1 Hz in eight HV; 10 Hz in eight migraineurs) on 5 consecutive days can modify VEPs for longer periods. In all eight HV, the 1 Hz rTMS-induced dishabituation increased in duration over consecutive sessions and persisted between several hours ( n = 4) and several weeks ( n = 4) after the fifth session. In six out eight migraineurs, the normalization of VEP habituation by 10 Hz rTMS lasted longer after each daily stimulation but did not exceed several hours after the last session, except in two patients, where it persisted for 2 days and 1 week. Daily rTMS can thus induce long-lasting changes in cortical excitability and VEP habituation pattern. Whether this effect may be useful in preventative migraine therapy remains to be determined.

scholarly journals Reliability of transcranial magnetic stimulation evoked potentials to detect the effects of theta-burst stimulation of the prefrontal cortex

2021 ◽  
Author(s):  
Adriano Henrique de Matos Moffa ◽  
Stevan Nikolin ◽  
Donel Martin ◽  
Colleen Loo ◽  
Tjeerd W. Boonstra
Keyword(s):  
Prefrontal Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Neural Excitability ◽  
Dorsolateral Prefrontal ◽  
Theta Burst

Background: Transcranial magnetic stimulation (TMS) with simultaneous electroencephalography (EEG) is a novel method for assessing cortical properties outside the motor region. Theta burst stimulation (TBS), a form of repetitive TMS, can non-invasively modulate cortical excitability and has been increasingly used to treat psychiatric disorders by targetting the dorsolateral prefrontal cortex (DLPFC). The TMS-evoked potentials (TEPs) analysis has been used to evaluate cortical excitability changes after TBS. However, it remains unclear whether TEPs can detect the neuromodulatory effects of TBS. Objectives: To confirm the reliability of TEP components within and between sessions and to measure changes in neural excitability induced by intermittent (iTBS) and continuous TBS (cTBS) applied to the left DLPFC. Methods: Test-retest reliability of TEPs and TBS-induced changes in cortical excitability were assessed in twenty-four healthy participants by stimulating the DLPFC in five separate sessions, once with sham and twice with iTBS and cTBS. EEG responses were recorded of 100 single TMS pulses before and after TBS, and the reproducibility measures were quantified with the concordance correlation coefficient (CCC). Results: The N100 and P200 components presented substantial reliability within the baseline block (CCCs>0.8) and moderate concordance between sessions (CCCmax≈0.7). Both N40 and P60 TEP amplitudes showed little concordance between sessions. Changes in TEP amplitudes after iTBS were marginally reliable for N100 (CCCmax=0.52), P200 (CCCmax=0.47) and P60 (CCCmax=0.40), presenting only fair levels of concordance at specific time points. Conclusions: The present findings show that only the N100 and P200 components had good concordance between sessions. The reliability of earlier components may have been affected by TMS-evoked artefacts. The poor reliability to detect changes in neural excitability induced by TBS indicates that TEPs do not provide a precise estimate of the changes in excitability in the DLPFC or, alternatively, that TBS did not induce consistent changes in neural excitability.

scholarly journals Assessing neuromodulation effects of theta burst stimulation to the prefrontal cortex using TMS-evoked potentials

2021 ◽  
Author(s):  
Adriano Henrique de Matos Moffa ◽  
Stevan Nikolin ◽  
Donel Martin ◽  
Colleen Loo ◽  
Tjeerd W. Boonstra
Keyword(s):  
Prefrontal Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Effect Size ◽  
Repeated Measures ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Theta Burst

Theta burst stimulation (TBS), a form of repetitive transcranial magnetic stimulation (TMS), is capable of non-invasively modulating cortical excitability. TBS is gaining popularity as a therapeutic tool for psychiatric disorders such as depression, in which the dorsolateral prefrontal cortex (DLPFC) is the main therapeutic target. However, the neuromodulatory effects of TBS on prefrontal regions remain unclear. An emerging tool to assess neuromodulation in non-motor regions is concurrent transcranial magnetic stimulation and electroencephalography (TMS-EEG) to measure TMS-evoked potentials (TEPs). We assessed twenty-four healthy participants (13 males, mean age 25.2±9.9 years) following intermittent TBS, continuous TBS, and sham applied to the left DLPFC using a double-blinded crossover design. TEPs were obtained at baseline and 2-, 15-, and 30-min post-stimulation. Four TEP components (N40, P60, N100 and P200) were analysed using mixed effects repeated measures models (MRMM). Results indicate no significant effects for any assessed components (all p>.05). The largest effect size (Cohens d = -0.5) comparing iTBS and sham was obtained for the N100 component at 15 minutes post-stimulation. This result was in the same direction but smaller than found in previous studies, suggesting that the true effect size may be lower than previously reported. Accurate estimates of the effects sizes and inter-individual heterogeneity will critically inform clinical applications using TEPs to assess the neuromodulatory effects of TBS.

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