Heterosynaptic Modulation of Motor Cortical Plasticity in Human
Bibliographic record
Abstract
Inductions of long-term potentiation (LTP) and depression (LTD) are modulated if they are preceded by a priming protocol, in a manner consistent with metaplasticity. Depotentiation refers to reversal of LTP by a subsequent protocol that has no effect by itself. Paired associative stimulation (PAS) at interstimulus interval of 25 ms (PAS25) and 10 ms (PAS10) produces spike timing-dependent LTP-like and LTD-like effects in human primary motor cortex. Continuous theta burst stimulation (cTBS) with 600 pulses produces an LTD-like effect, whereas cTBS with 150 pulses (cTBS150) has no effect by itself. We investigated whether cortical plasticity induced by PAS can be modulated by heterosynaptic inputs of cTBS150. PAS25 and PAS10 primed and followed by cTBS150 were compared withPAS25 and PAS10 alone. Motor evoked potential (MEP) amplitude, recruitment curve, and intracortical circuits including short-interval intracortical inhibition (SICI), long-interval intracortical inhibition (LICI), intracortical facilitation, and short-latency afferent inhibition were measured before and after the interventions. After PAS25 alone, MEP amplitude increased while intracortical circuits did not change. A priming cTBS150 enhanced the effects of PAS25 with further increase in MEP amplitude and led to reduction in SICI and LICI. PAS25 followed by cTBS150 led to reduced MEP amplitude and increased LICI and SICI. Both priming and following cTBS150 reversed the LTD-like effect produced by PAS10 with little change in intracortical circuits. We conclude that cortical plasticity induced by PAS and cTBS interacts in a heterosynaptic and bidirectional manner. The order of the interventions determines whether the underlying mechanisms are related to metaplasticity or depotentiation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.004 |
| 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) | 0.000 | 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 teacher head, 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".