The minimal number of TMS trials required for the reliable assessment of corticospinal excitability, short interval intracortical inhibition, and intracortical facilitation

Biabani, Mana; Farrell, Michael J.; Zoghi, Maryam; Egan, Gary F.; Jaberzadeh, Shapour

doi:10.1016/j.neulet.2018.03.026

Cited by 72 publications

(74 citation statements)

References 36 publications

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“…As is well established, MEPs are inherently variable due to the fluctuating nature of corticospinal and motoneuronal excitability (Ellaway et al., ; Kiers, Cros, Chiappa, & Fang, ), randomness in the firing of pyramidal tract neurons and spinal motoneurons (Pitcher, Ogston, & Miles, ) as well as desynchronisation of action potentials (Magistris, Rösler, Truffert, & Myers, ). The variability of responses observed in the present study is comparable to that reported previously when similar numbers of pulses were employed (Biabani, Farrell, Zoghi, Egan, & Jaberzadeh, ; Brownstein, Ansdell, Škarabot, Howatson, et al., ). A greater variability in MEPs compared to LEPs can perhaps be explained by differences in the complexity of the responses to TMS as opposed to LS as discussed above.…”

Section: Discussionsupporting

confidence: 90%

Electrical stimulation of human corticospinal axons at the level of the lumbar spinal segments

Škarabot

Ansdell

Brownstein

et al. 2019

Eur J of Neuroscience

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Electrical stimulation over the mastoids or thoracic spinous processes has been used to assess subcortical contribution to corticospinal excitability, but responses are difficult to evoke in the resting lower limbs or are limited to only a few muscle groups. This might be mitigated by delivering the stimuli lower on the spinal column, where the descending tracts contain a greater relative density of motoneurons projecting to lower limb muscles. We investigated activation of the corticospinal axons innervating tibialis anterior (TA) and rectus femoris (RF) by applying a single electrical stimulus over the first lumbar spinous process (LS). LS was paired with transcranial magnetic stimulation (TMS) at interstimulus intervals (ISIs) of −16 (TMS before LS) to 14 ms (LS before TMS). The relationship between muscle contraction strength (10%–100% maximal) and the amplitude of single‐pulse TMS and LS responses was also investigated. Compared to the responses to TMS alone, responses to paired stimulation were significantly occluded in both muscles for ISIs ≥−8 ms (p ≤ 0.035), consistent with collision of descending volleys from TMS with antidromic volleys originating from LS. This suggests that TMS and LS activate some of the same corticospinal axons. Additionally, the amplitude of TMS and LS responses increased with increasing contraction strengths with no change in onset latency, suggesting responses to LS are evoked transsynaptically and have a monosynaptic component. Taken together, these experiments provide evidence that LS is an alternative method that could be used to discern segmental changes in the corticospinal tract when targeting lower limb muscles.

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Section: Discussionsupporting

confidence: 90%

Electrical stimulation of human corticospinal axons at the level of the lumbar spinal segments

Škarabot

Ansdell

Brownstein

et al. 2019

Eur J of Neuroscience

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“…The CV (SD/meanx100) represents the range, or percentage variance that one SD of the data lies about the mean (Atkinson & Nevill, 1998). Its simplicity has led to use in NIBS and TMS literature (eg: (Biabani et al, 2018;Klein-Flugge et al, 2013;Sadnicka et al, 2013;Martin V. Sale et al, 2017;Temesi et al, 2017;Vassiliadis et al, 2018)).…”

Section: Response Variabilitymentioning

confidence: 99%

The effects of transcranial direct current stimulation on corticospinal and cortico-cortical excitability and response variability: conventional versus high-definition montages

Pellegrini

Zoghi

Jaberzadeh

2020

Preprint

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Response variability following transcranial direct current stimulation (tDCS) highlights need for exploring different tDCS electrode montages. This study compared corticospinal excitability (CSE), cortico-cortical excitability and intra-individual variability following conventional and HD anodal (a-tDCS) and cathodal (c-tDCS) tDCS. Fifteen healthy young males attended four sessions at least one-week apart: conventional a-tDCS, conventional c-tDCS, HD-a-tDCS, HD-c-tDCS. TDCS was administered (1mA, 10-minutes) over the primary motor cortex (M1), via 6x4cm active and 7x5cm return electrodes (conventional tDCS) and 4x1 ring-electrodes 3.5cm apart in ring formation around M1 (HD-tDCS). For CSE, twenty-five single-pulse transcranial magnetic stimulation (TMS) peakto-peak motor evoked potentials (MEP) were recorded at baseline, 0-minutes and 30-minutes post-tDCS. For cortico-cortical excitability, twenty-five paired-pulse MEPs with 3-millisecond (ms) inter-pulse interval (IPI) and twenty-five at 10ms assessed short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) respectively. MEP standardised z-values standard deviations represented intra-individual variability. No significant differences were reported in CSE between conventional and HD a-tDCS, but significant differences between conventional and HD c-tDCS 0-minutes post-tDCS. Intra-individual variability was significantly reduced in conventional tDCS compared to HD-tDCS for a-tDCS (0-minutes) and c-tDCS (30-minutes). No significant changes were reported in SICI and ICF. These novel findings highlight current technical issues with HD-tDCS, suggesting future tDCS studies should utilise conventional tDCS to minimise intraindividual variability, ensuring tDCS after-effects are true changes in CSE and cortico-cortical excitability.

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“…There were trials in each Simple condition, two of which were catch trials. We recorded 20 baseline MEPs for each condition and 20 MEPs for each cue condition in the delay period, a sample size recommended to obtain reliable MEP measures (Biabani et al, 2018). The blocks lasted approximately eight and six minutes for the Choice and Simple RT conditions, respectively.…”

Section: Delayed-response Taskmentioning

confidence: 99%

Planning face, hand, and leg movements: anatomical constraints on preparatory inhibition

Labruna

Tischler

Cazares

et al. 2019

Journal of Neurophysiology

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Motor-evoked potentials (MEPs), elicited by transcranial magnetic stimulation (TMS) over the motor cortex, are reduced during the preparatory period in delayed response tasks. In this study we examined how MEP suppression varies as a function of the anatomical organization of the motor cortex. MEPs were recorded from a left index muscle while participants prepared a hand or leg movement in experiment 1 or prepared an eye or mouth movement in experiment 2. In this manner, we assessed if the level of MEP suppression in a hand muscle varied as a function of the anatomical distance between the agonist for the forthcoming movement and the muscle targeted by TMS. MEP suppression was attenuated when the cued effector was anatomically distant from the hand (e.g., leg or facial movement compared with finger movement). A similar effect was observed in experiment 3 in which MEPs were recorded from a muscle in the leg and the forthcoming movement involved the upper limb or face. These results demonstrate an important constraint on preparatory inhibition: it is sufficiently broad to be manifest in a muscle that is not involved in the task, but it is not global, showing a marked attenuation when the agonist muscle belongs to a different segment of the body. NEW & NOTEWORTHY Using transcranial magnetic stimulation, we examined changes in corticospinal excitability as people prepared to move. Consistent with previous work, we observed a reduction in excitability during the preparatory period, an effect observed in both task-relevant and task-irrelevant muscles. However, this preparatory inhibition is anatomically constrained, attenuated in muscles belonging to a different body segment than the agonist of the forthcoming movement.

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The minimal number of TMS trials required for the reliable assessment of corticospinal excitability, short interval intracortical inhibition, and intracortical facilitation

Cited by 72 publications

References 36 publications

Electrical stimulation of human corticospinal axons at the level of the lumbar spinal segments

Electrical stimulation of human corticospinal axons at the level of the lumbar spinal segments

The effects of transcranial direct current stimulation on corticospinal and cortico-cortical excitability and response variability: conventional versus high-definition montages

Planning face, hand, and leg movements: anatomical constraints on preparatory inhibition

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