Transcranial magnetic stimulation input–output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortex
Measurement of the input–output (IO) curves of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) can be used to assess corticospinal excitability and motor recruitment. While IO curves have been used to study disease and pharmacology, few studies have compared the IO...
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Frontiers Media S.A.
2024-02-01
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| Series: | Frontiers in Human Neuroscience |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fnhum.2024.1310320/full |
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| author | Lari M. Koponen Lari M. Koponen Miles Martinez Miles Martinez Miles Martinez Eleanor Wood David L. K. Murphy Stefan M. Goetz Stefan M. Goetz Stefan M. Goetz Lawrence G. Appelbaum Lawrence G. Appelbaum Angel V. Peterchev Angel V. Peterchev Angel V. Peterchev Angel V. Peterchev |
| author_facet | Lari M. Koponen Lari M. Koponen Miles Martinez Miles Martinez Miles Martinez Eleanor Wood David L. K. Murphy Stefan M. Goetz Stefan M. Goetz Stefan M. Goetz Lawrence G. Appelbaum Lawrence G. Appelbaum Angel V. Peterchev Angel V. Peterchev Angel V. Peterchev Angel V. Peterchev |
| author_sort | Lari M. Koponen |
| collection | DOAJ |
| description | Measurement of the input–output (IO) curves of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) can be used to assess corticospinal excitability and motor recruitment. While IO curves have been used to study disease and pharmacology, few studies have compared the IO curves across the body. This study sought to characterize IO curve parameters across the dominant and non-dominant sides of upper and lower limbs in healthy participants. Laterality preferences were assessed in eight healthy participants and IO curves were measured bilaterally for the first dorsal interosseous (FDI), biceps brachii (BB), and tibialis anterior (TA) muscles. Results show that FDI has lower motor threshold than BB which is, in turn, lower than TA. In addition, both BB and TA have markedly shallower logarithmic IO curve slopes from small to large MEP responses than FDI. After normalizing these slopes by their midpoints to account for differences in motor thresholds, which could result from geometric factors such as the target depth, large differences in logarithmic slopes remain present between all three muscles. The differences in slopes between the muscles could not be explained by differences in normalized IO curve spreads, which relate to the extent of the cortical representation and were comparable across the muscles. The IO curve differences therefore suggest muscle-dependent variations in TMS-evoked recruitment across the primary motor cortex, which should be considered when utilizing TMS-evoked MEPs to study disease states and treatment effects. |
| first_indexed | 2024-03-08T05:13:14Z |
| format | Article |
| id | doaj.art-799baa4579124c58a1d9154aab67c777 |
| institution | Directory Open Access Journal |
| issn | 1662-5161 |
| language | English |
| last_indexed | 2024-03-08T05:13:14Z |
| publishDate | 2024-02-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Human Neuroscience |
| spelling | doaj.art-799baa4579124c58a1d9154aab67c7772024-02-07T05:16:26ZengFrontiers Media S.A.Frontiers in Human Neuroscience1662-51612024-02-011810.3389/fnhum.2024.13103201310320Transcranial magnetic stimulation input–output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortexLari M. Koponen0Lari M. Koponen1Miles Martinez2Miles Martinez3Miles Martinez4Eleanor Wood5David L. K. Murphy6Stefan M. Goetz7Stefan M. Goetz8Stefan M. Goetz9Lawrence G. Appelbaum10Lawrence G. Appelbaum11Angel V. Peterchev12Angel V. Peterchev13Angel V. Peterchev14Angel V. Peterchev15Department of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, United StatesCentre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, UKDepartment of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, United StatesCenter for Cognitive Neuroscience, Duke University, Durham, NC, United StatesDepartment of Electrical and Computer Engineering, Duke University, Durham, NC, United StatesDepartment of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, United StatesDepartment of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, United StatesDepartment of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, United StatesDepartment of Electrical and Computer Engineering, Duke University, Durham, NC, United StatesDepartment of Neurosurgery, Duke University, Durham, NC, United StatesDepartment of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, United StatesDepartment of Psychiatry, University of California, San Diego, San Diego, CA, United StatesDepartment of Psychiatry and Behavioral Sciences, Duke University, Durham, NC, United StatesDepartment of Electrical and Computer Engineering, Duke University, Durham, NC, United StatesDepartment of Neurosurgery, Duke University, Durham, NC, United StatesDepartment of Biomedical Engineering, Duke University, Durham, NC, United StatesMeasurement of the input–output (IO) curves of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) can be used to assess corticospinal excitability and motor recruitment. While IO curves have been used to study disease and pharmacology, few studies have compared the IO curves across the body. This study sought to characterize IO curve parameters across the dominant and non-dominant sides of upper and lower limbs in healthy participants. Laterality preferences were assessed in eight healthy participants and IO curves were measured bilaterally for the first dorsal interosseous (FDI), biceps brachii (BB), and tibialis anterior (TA) muscles. Results show that FDI has lower motor threshold than BB which is, in turn, lower than TA. In addition, both BB and TA have markedly shallower logarithmic IO curve slopes from small to large MEP responses than FDI. After normalizing these slopes by their midpoints to account for differences in motor thresholds, which could result from geometric factors such as the target depth, large differences in logarithmic slopes remain present between all three muscles. The differences in slopes between the muscles could not be explained by differences in normalized IO curve spreads, which relate to the extent of the cortical representation and were comparable across the muscles. The IO curve differences therefore suggest muscle-dependent variations in TMS-evoked recruitment across the primary motor cortex, which should be considered when utilizing TMS-evoked MEPs to study disease states and treatment effects.https://www.frontiersin.org/articles/10.3389/fnhum.2024.1310320/fulltranscranial magnetic stimulationTMSmotor evoked potentialMEPinput–output curveIO curve |
| spellingShingle | Lari M. Koponen Lari M. Koponen Miles Martinez Miles Martinez Miles Martinez Eleanor Wood David L. K. Murphy Stefan M. Goetz Stefan M. Goetz Stefan M. Goetz Lawrence G. Appelbaum Lawrence G. Appelbaum Angel V. Peterchev Angel V. Peterchev Angel V. Peterchev Angel V. Peterchev Transcranial magnetic stimulation input–output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortex Frontiers in Human Neuroscience transcranial magnetic stimulation TMS motor evoked potential MEP input–output curve IO curve |
| title | Transcranial magnetic stimulation input–output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortex |
| title_full | Transcranial magnetic stimulation input–output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortex |
| title_fullStr | Transcranial magnetic stimulation input–output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortex |
| title_full_unstemmed | Transcranial magnetic stimulation input–output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortex |
| title_short | Transcranial magnetic stimulation input–output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortex |
| title_sort | transcranial magnetic stimulation input output curve slope differences suggest variation in recruitment across muscle representations in primary motor cortex |
| topic | transcranial magnetic stimulation TMS motor evoked potential MEP input–output curve IO curve |
| url | https://www.frontiersin.org/articles/10.3389/fnhum.2024.1310320/full |
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