Origin of muscle action potentials evoked by transcranial magnetic stimulation in cats.

PAPER pubmed Neurological research 1995 Animal study Effect: unclear Evidence: Low

Read original paper → PMID: 8622805 Evidence Lab

Abstract

We studied the effects of transcranial magnetic stimulation on ipsilateral and contralateral forelimb extensor muscles in anesthetized cats. A magnetic stimulator, operating at 100% intensity, was used through a circular coil, which was placed tangentially over the midline scalp. Bilateral activation of extensor muscles was readily obtained in all animals. The onset latencies were 7.3 +/- 1.1 and 7.07 +/- 0.8 msec for the contralateral and ipsilateral muscles, respectively. The amplitude of muscle response was unstable in magnitude, nevertheless, it did not show any significant difference between the two sides. The latency of response for ipsilateral and contralateral muscles was similar, which suggests simultaneous activation of motor pathways servicing forelimb muscles. Lesioning or ablation of the motor cortex and decerebration at mid-colliculi level did not abolish the evoked responses elicited at high intensity magnetic stimulation. Stereotactic electrical stimulation of the vestibular nuclei complex was performed, and satisfactory ipsilateral motor responses were obtained. Subsequently, a stereotactic radiofrequency lesion was made at the vestibular nuclei complex, with morphological confirmation. After this lesion, the motor evoked potentials (MEPs) were significantly diminished in amplitude. This finding strongly suggests that the generator of the MEPs resides in the brainstem, mainly at the vestibular nuclei complex.

AI evidence extraction

At a glance

Study type

Animal study

Effect direction

unclear

Population

Anesthetized cats

Sample size

—

Exposure

transcranial magnetic stimulation (TMS)

Evidence strength

Low

Confidence: 74% · Peer-reviewed: yes

Main findings

High-intensity transcranial magnetic stimulation elicited bilateral forelimb extensor muscle responses in all animals with similar onset latencies on both sides. Lesioning/ablation of motor cortex and decerebration did not abolish responses, while a radiofrequency lesion of the vestibular nuclei complex significantly diminished MEP amplitude, suggesting a brainstem (vestibular nuclei complex) generator for these MEPs under the conditions tested.

Outcomes measured

Forelimb extensor muscle activation (ipsilateral and contralateral)
Onset latency of muscle responses
Amplitude of motor evoked potentials (MEPs)
Effect of motor cortex lesion/ablation and decerebration on evoked responses
Effect of vestibular nuclei electrical stimulation and radiofrequency lesion on MEP amplitude

Limitations

Sample size not reported in abstract
Exposure parameters beyond '100% intensity' and coil placement are not quantified (e.g., pulse characteristics/field strength)
Animal, anesthetized preparation may limit generalizability

View raw extracted JSON

{
    "study_type": "animal",
    "exposure": {
        "band": null,
        "source": "transcranial magnetic stimulation (TMS)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Anesthetized cats",
    "sample_size": null,
    "outcomes": [
        "Forelimb extensor muscle activation (ipsilateral and contralateral)",
        "Onset latency of muscle responses",
        "Amplitude of motor evoked potentials (MEPs)",
        "Effect of motor cortex lesion/ablation and decerebration on evoked responses",
        "Effect of vestibular nuclei electrical stimulation and radiofrequency lesion on MEP amplitude"
    ],
    "main_findings": "High-intensity transcranial magnetic stimulation elicited bilateral forelimb extensor muscle responses in all animals with similar onset latencies on both sides. Lesioning/ablation of motor cortex and decerebration did not abolish responses, while a radiofrequency lesion of the vestibular nuclei complex significantly diminished MEP amplitude, suggesting a brainstem (vestibular nuclei complex) generator for these MEPs under the conditions tested.",
    "effect_direction": "unclear",
    "limitations": [
        "Sample size not reported in abstract",
        "Exposure parameters beyond '100% intensity' and coil placement are not quantified (e.g., pulse characteristics/field strength)",
        "Animal, anesthetized preparation may limit generalizability"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "transcranial magnetic stimulation",
        "motor evoked potentials",
        "cats",
        "brainstem",
        "vestibular nuclei",
        "forelimb extensor muscles",
        "latency",
        "radiofrequency lesion"
    ],
    "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract/metadata and may be incomplete or incorrect. This content is for informational purposes only and is not medical advice.

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