Automated TMS hotspot-hunting using a closed loop threshold-based algorithm

Meincke, J.; Hewitt, Manuel; Batsikadze, Giorgi; Liebetanz, David

doi:10.1016/j.neuroimage.2015.09.013

Cited by 36 publications

(29 citation statements)

References 47 publications

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“…Nonetheless, future studies should consider increasing the number of TMS trials in order to improve reliability. Another approach to reduce TMS variability reported by Meincke and colleagues (2016) is using a fully automated hotspot-search procedure based on an algorithm that takes into account the RMT instead of MEP amplitudes [61]. …”

Section: Discussionmentioning

confidence: 99%

Response variability of different anodal transcranial direct current stimulation intensities across multiple sessions

2017

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Background It is well known that transcranial direct current stimulation (tDCS) is capable of modulating corticomotor excitability. However, a source of growing concern has been the observed inter- and intra-individual variability of tDCS-responses. Recent studies have assessed whether individuals respond in a predictable manner across repeated sessions of anodal tDCS (atDCS). The findings of these investigations have been inconsistent, and their methods have some limitations (i.e. lack of sham condition or testing only one tDCS intensity). Objective To study inter- and intra-individual variability of atDCS effects at two different intensities on primary motor cortex (M1) excitability. Methods Twelve subjects participated in a crossover study testing 7-min atDCS over M1 in three separate conditions (2mA, 1mA, sham) each repeated three times separated by 48hrs. Motor evoked potentials were recorded before and after stimulation (up to 30min). Time of testing was maintained consistent within participants. To estimate the reliability of tDCS effects across sessions, we calculated the Intra-class Correlation Coefficient (ICC). Results AtDCS at 2mA, but not 1mA, significantly increased cortical excitability at the group level in all sessions. The overall ICC revealed fair to high reliability of tDCS effects for multiple sessions. Given that the distribution of responses showed important variability in the sham condition, we established a Sham Variability-Based Threshold to classify responses and to track individual changes across sessions. Using this threshold an intra-individual consistent response pattern was then observed only for the 2mA condition. Conclusion 2mA anodal tDCS results in consistent intra- and inter-individual increases of M1 excitability.

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Section: Discussionmentioning

confidence: 99%

Response variability of different anodal transcranial direct current stimulation intensities across multiple sessions

2017

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“…The hotspot is the coil position and orientation on the scalp that allows the TMS-induced magnetic field to best activate the targeted corticospinal neurons (e.g. pyramidal tract neurons controlling the right tibialis anterior muscle), providing the lowest threshold and shortest latency of TMS-evoked responses (Malcolm et al, 2006; Meincke, Hewitt, Batsikadze, & Liebetanz, 2016; Rossini et al, 1994). An increase in TMS-derived motor map area may signify greater cortical excitability, a larger area of functionally-relevant muscle representation, or that the targeted muscle representation can be activated from more remote scalp locations (Butler et al, 2005; Wassermann et al, 1992; Wolf et al, 2004).…”

Section: The Use Of Tms For Studying Lower Limb Musculature Presents mentioning

confidence: 99%

The use of transcranial magnetic stimulation to evaluate cortical excitability of lower limb musculature: Challenges and opportunities

Kesar

Stinear

Wolf

2018

RNN

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Neuroplasticity is a fundamental yet relatively unexplored process that can impact rehabilitation of lower extremity (LE) movements. Transcranial magnetic stimulation (TMS) has gained widespread application as a non-invasive brain stimulation technique for evaluating neuroplasticity of the corticospinal pathway. However, a majority of TMS studies have been performed on hand muscles, with a paucity of TMS investigations focused on LE muscles. This perspective review paper proposes that there are unique methodological challenges associated with using TMS to evaluate corticospinal excitability of lower limb muscles. The challenges include: (1) the deeper location of the LE motor homunculus; (2) difficulty with targeting individual LE muscles during TMS; and (3) differences in corticospinal circuity controlling upper and lower limb muscles. We encourage future investigations that modify traditional methodological approaches to help address these challenges. Systematic TMS investigations are needed to determine the extent of overlap in corticomotor maps for different LE muscles. A simple, yet informative methodological solution involves simultaneous recordings from multiple LE muscles, which will provide the added benefit of observing how other relevant muscles co-vary in their responses during targeted TMS assessment directed toward a specific muscle. Furthermore, conventionally used TMS methods (e.g., determination of hot spot location and motor threshold) may need to be modified for TMS studies involving LE muscles. Additional investigations are necessary to determine the influence of testing posture as well as activation state of adjacent and distant LE muscles on TMS-elicited responses. An understanding of these challenges and solutions specific to LE TMS will improve the ability of neurorehabilitation clinicians to interpret TMS literature, and forge novel future directions for neuroscience research focused on elucidating neuroplasticity processes underlying locomotion and gait training.

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“…Combining nTMS maps with individual MRIs facilitated—as a first step on the way—the analysis of group data in normalized space [15, 26, 27]. Previous nTMS approaches, however, still projected the TMS coil positions as a grid of target points on the brain surface, resembling a plane that covered both gyri and sulci, and did not account for differences in cortex morphology [15, 17–19, 28–30]. To overcome this limitation, we recently proposed a novel projection, interpolation, and coregistration technique for estimating nTMS sites onto the individual anatomy, namely, by following the surface curvature of gyri [31].…”

Section: Introductionmentioning

confidence: 99%

Neuromuscular Plasticity: Disentangling Stable and Variable Motor Maps in the Human Sensorimotor Cortex

Kraus

Gharabaghi

2016

Neural Plasticity

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Motor maps acquired with transcranial magnetic stimulation (TMS) are evolving as a biomarker for monitoring disease progression or the effects of therapeutic interventions. High test-retest reliability of this technique for long observation periods is therefore required to differentiate daily or weekly fluctuations from stable plastic reorganization of corticospinal connectivity. In this study, a novel projection, interpolation, and coregistration technique, which considers the individual gyral anatomy, was applied in healthy subjects for biweekly acquired TMS motor maps over a period of twelve weeks. The intraclass correlation coefficient revealed long-term reliability of motor maps with relevant interhemispheric differences. The sensorimotor cortex and nonprimary motor areas of the dominant hemisphere showed more extended and more stable corticospinal connectivity. Long-term correlations of the MEP amplitudes at each stimulation site revealed mosaic-like clusters of consistent corticospinal excitability. The resting motor threshold, centre of gravity, and mean MEPs across all TMS sites, as highly reliable cortical map parameters, could be disentangled from more variable parameters such as MEP area and volume. Cortical TMS motor maps provide high test-retest reliability for long-term monitoring when analyzed with refined techniques. They may guide restorative interventions which target dormant corticospinal connectivity for neurorehabilitation.

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Automated TMS hotspot-hunting using a closed loop threshold-based algorithm

Cited by 36 publications

References 47 publications

Response variability of different anodal transcranial direct current stimulation intensities across multiple sessions

Response variability of different anodal transcranial direct current stimulation intensities across multiple sessions

The use of transcranial magnetic stimulation to evaluate cortical excitability of lower limb musculature: Challenges and opportunities

Neuromuscular Plasticity: Disentangling Stable and Variable Motor Maps in the Human Sensorimotor Cortex

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