Ipsilateral contraction increases map area and decreases motor threshold for contralateral hand muscle
Bibliographic record
Abstract
Ipsilateral motor pathways projecting from primary motor cortex (M1) to the distal upper limb exist in humans, and activation of these ipsilateral pathways also facilitate corticomotor excitability of the contralateral homologous muscle. Handedness and biological sex potentially influence the motor cortical representations, however their influence on ipsilateral representations remain largely unexplored. Here, we investigated the effects of ipsilateral contraction on hand motor representation size and excitability, and examined whether these effects were dependent on handedness and/or biological sex. In 80 individuals (40 right-handed, 40-left handed, equal males and females), we performed transcranial magnetic stimulation (TMS) to obtain motor threshold and motor map area of the contralateral first dorsal interosseus (FDI) muscle of each hemisphere, at (1) rest and during (2) ipsilateral FDI muscle contraction at approximately 10% of maximum voluntary contraction. Results showed that ipsilateral contraction increased motor map area and decreased motor threshold within M1. These changes were independent of handedness and biological sex, and similar between hemispheres. Our findings demonstrate that an ipsilateral hand contraction increases the size and excitability of motor representations within ipsilateral M1, and these increases are irrespective of one's handedness and biological sex.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".