Conventional or threshold-hunting TMS? A tale of two SICIs

Cirillo, John; Semmler, John G.; Mooney, Ronan A.; Byblow, Winston D.

doi:10.1016/j.brs.2018.07.047

Cited by 22 publications

(35 citation statements)

References 49 publications

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“…6A between SICI assessed by threshold-tracking (T-SICI) and that assessed by conventional amplitude measurements (A-SICI), was closer than might have been expected, with almost 97% of the variance in mean T-SICIp values accounted for by the logarithmic relationship with the A-SICI geometric means. We were comparing independent SICI methods, so that no attempt was made to match the MEP amplitudes, as was done in a previous A-SICI/T-SICI comparison [14]: T-SICI used a target response of 0.2 mV, while A-SICI started with a target response of 1 mV. The present finding of a good correlation between A-SICI and T-SICIp across a range of ISIs extends a previous finding that a correlation is maintained across conditions with both comparable and non-comparable test stimulus intensities [11].…”

Section: Relationship Between A-sici and T-sicimentioning

confidence: 99%

“…Just as resting motor threshold (RMT) can be measured in different ways [12,13], so can the threshold for a conditioned response. For example, adaptive threshold hunting has been used by Cirillo and colleagues [14], using a 'maximum-likelihood parameter estimation by sequential testing' (PEST) [15,16]. To make an accurate comparison between the constant response and constant stimulus measures of SICI, they matched the conditioned and test stimulus intensities between the two approaches, so that the measurements were not independent.…”

Section: Introductionmentioning

confidence: 99%

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Short-interval intracortical inhibition as a function of inter-stimulus interval: Three methods compared

et al. 2021

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Background: Short-interval intracortical inhibition (SICI), as measured by threshold-tracking as a function of inter-stimulus interval (ISI), has been proposed as a useful biomarker for amyotrophic lateral sclerosis (ALS), but its relationship to conventional amplitude measurements has not been established. Methods: Serial tracking of SICI at increasing ISIs from 1 to 7 ms (T-SICIs) was compared in 50 healthy control subjects with the same ISIs tracked in parallel (T-SICIp), and with conventional amplitude measurements (A-SICI). For T-SICIp and A-SICI, pairs of conditioning and test stimuli with different ISIs were pseudo-randomised and interspersed with test-alone stimuli given at regular intervals. Thresholds were estimated by regression of log peak-to-peak amplitude on stimulus. Results: T-SICIp and A-SICI were closely related: a tenfold reduction in amplitude corresponding to an approximately 18% increase in threshold. Threshold increases were greater for T-SICIs than for T-SICIp at 3.5e5 ms (P < 0.001). This divergence depended on the initial settings and whether ISIs were progressively increased or decreased, and was attributed to the limitations of the serial tracking protocol. SICI variability between subjects was greatest for T-SICIs estimates and least for A-SICI, and only A-SICI estimates revealed a significant decline in inhibition with age. Conclusions: The serial tracking protocol did not accurately show the dependence of inhibition on ISI. Randomising ISIs gives corresponding SICI measures, whether tracking thresholds or measuring amplitude measurements. SICI variability suggested that A-SICI measurements may be the most sensitive to loss of inhibition.

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Section: Relationship Between A-sici and T-sicimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Short-interval intracortical inhibition as a function of inter-stimulus interval: Three methods compared

et al. 2021

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“…For both experiments, the order of the experimental conditions was randomized across participants. An available online freeware (TMS Motor Threshold Assessment Tool, MTAT 2.0), based on a maximum-likelihood Parameter Estimation by Sequential Testing (PEST) strategy was used with "assessment without a priori information" in line with previous studies Cirillo et al, 2018). The stimulation sequence always began with the TS at 37 %MSO.…”

Section: Adaptive Threshold-hunting Techniquementioning

confidence: 99%

“…To do so, we designed a pair of experiments in which we varied the CS intensity and determined the TS intensity required to maintain a fixed MEP amplitude for each condition using an adaptive threshold hunting technique (Awiszus et al, 1999;Fisher et al, 2002;Awiszus, 2003;Samusyte et al, 2018;Vucic et al, 2018). This method has been recently developed in order to overcome the potential limitations of conventional paired-pulse TMS protocols, such as large variability in MEP amplitude and a "floor/ceiling effect" when the observed inhibition leads to complete MEP suppression Cirillo et al, 2018;Van den Bos et al, 2018). The adaptive threshold-hunting technique provides a new opportunity to extend our understanding of physiological mechanisms underlying intracortical inhibition in healthy subjects and it has been recently shown to be more reliable with shorter acquisition time than conventional SICI techniques (Samusyte et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Unravelling the modulation of intracortical inhibition during motor imagery: An adaptive threshold-hunting study

Neige

Rannaud-Monany

Stinear

et al. 2019

Preprint

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Motor imagery (MI) is the mental simulation of an action without any apparent muscular contraction. By means of transcranial magnetic stimulation, few studies revealed a decrease of short-interval intracortical inhibition (SICI) within the primary motor cortex. However, this decrease is ambiguous, as one would expect greater inhibition during MI to prevent overt motor output. The current study investigated the extent of SICI modulation during MI through a methodological and a conceptual reconsideration of i) the importance of parameters to assess SICI (Exp.1) and ii) the inhibitory process within the primary motor cortex as an inherent feature of MI (Exp.2). Participants performed two tasks: 1) rest and 2) imagery of isometric abduction of the right index finger. Using transcranial magnetic stimulation, motor evoked potentials were elicited in the right first dorsal interosseous muscle. An adaptive threshold-hunting paradigm was used, where the stimulus intensity required to maintain a fixed motor evoked potential amplitude was quantified.To test SICI, we conditioned the test stimulus with a conditioning stimulus (CS) of different intensities. Results revealed an Intensity by Task interaction showing that SICI decreased during MI as compared to rest only for the higher CS intensity (Exp.1). At the lowest CS intensities, a Task main effect revealed that SICI increased during MI (Exp.2). SICI modulation during MI depends critically on the CS intensity. By optimising CS intensity, we have shown that SICI circuits may increase during MI, revealing a potential mechanism to prevent the production of a movement while the motor system is activated.

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“…To do so, we designed a pair of experiments in which we varied the CS intensity and determined the TS intensity required to maintain a fixed MEP amplitude for each condition using an adaptive threshold hunting technique (Awiszus et al, 1999;Fisher et al, 2002;Awiszus, 2003;Samusyte et al, 2018;Vucic et al, 2018). This method has been recently developed in order to overcome the potential limitations of conventional paired-pulse TMS protocols, such as large variability in MEP amplitude and a "floor/ceiling effect" when the observed inhibition leads to complete MEP suppression (Cirillo and Byblow, 2016;Cirillo et al, 2018;Van den Bos et al, 2018). The adaptive threshold-hunting technique provides a new opportunity to extend our understanding of physiological mechanisms underlying intracortical inhibition in healthy subjects and it has been recently shown to be more reliable with shorter acquisition time than conventional SICI techniques (Samusyte et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Unravelling the Modulation of Intracortical Inhibition During Motor Imagery: An Adaptive Threshold-Hunting Study

et al. 2020

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Conventional or threshold-hunting TMS? A tale of two SICIs

Cited by 22 publications

References 49 publications

Short-interval intracortical inhibition as a function of inter-stimulus interval: Three methods compared

Short-interval intracortical inhibition as a function of inter-stimulus interval: Three methods compared

Unravelling the modulation of intracortical inhibition during motor imagery: An adaptive threshold-hunting study

Unravelling the Modulation of Intracortical Inhibition During Motor Imagery: An Adaptive Threshold-Hunting Study

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