Does temporary inhibition of the human primary motor cortex alter resting and isometric handgrip exercise‐mediated sympathetic neural responses?
Bibliographic record
Abstract
Resting muscle sympathetic nerve activity (MSNA) is elevated in stroke patients with damage encompassing the primary motor cortex (M1) and during single‐pulse, inhibitory transcranial magnetic stimulation (TMS) protocols over M1 in healthy participants. These findings suggest a suppressive role of M1 on resting levels of MSNA. It is currently unclear whether inhibition of M1 alters resting and/or exercise‐mediated sympathetic activity in humans. We tested the hypothesis that temporary inhibition of the contralateral hand region of M1 would exaggerate resting and isometric handgrip exercise (IHG)‐mediated MSNA. 12 (7♀) young, healthy (23±3 years, 25±3 kg•m −2 ) participants were instrumented for recordings of fibular MSNA (microneurography), heart rate (HR, electrocardiography), and non‐invasive blood pressure (BP, Portapres®). These measures were collected at rest, during 2 minutes of IHG (35% maximum effort) and 2 minutes of post‐exercise ischemia (PEI). This protocol was repeated under the following theta burst TMS (TBS) conditions: Sham (no TBS), continuous TBS (cTBS, Inhibitory) and intermittent TBS (iTBS, Facilitatory). Sham was always performed first followed by randomly assigned cTBS and iTBS conditions. Compared to Sham (30±7 bursts•100 heartbeats −1 ), MSNA burst incidence was higher (p<0.02) five minutes following cTBS (42±13 bursts•100 heartbeats −1 ) but unchanged (p=0.49) after iTBS (30±12 bursts•100 heartbeats −1 ). Resting HR and mean arterial BP (MAP) recorded during Sham were unchanged (all, p>0.51) following iTBS and cTBS. From rest, MSNA increased (p<0.05) after IHG (38±9 bursts•minute −1 ) and remained elevated following PEI (37±8 bursts•minute −1 ) during the Sham condition. Furthermore, HR and MAP responses peaked (both, p < 0.01) after 2‐minutes of IHG but returned to resting levels following PEI. These MSNA and cardiovascular responses to IHG and PEI were not different (all, p>0.37) in the cTBS and iTBS conditions. In conclusion, temporary inhibition of the hand region in M1 via cTBS produced a transient sympathoexcitation but did not alter resting HR or MAP. Neither facilitatory (iTBS) nor inhibitory (cTBS) stimulation protocols altered IHG‐mediated sympathetic or cardiovascular reflex responses. These findings warrant future investigation aimed at determining whether cTBS protocols can reduce resting MSNA in patient populations characterized by exaggerated sympathoexcitation (e.g., resistant hypertension, ischemic stroke). Support or Funding Information Support provided by: Canadian Foundation for Innovation: Leaders Opportunity Fund
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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".