Abstract

Objective

Scalp-recorded evoked potentials elicited by applying afferent electrical stimulation at the tragus region of the human external ear have shown inconsistent results. We aim to disentangle discrepant findings and interpretations, and put forward novel physiological explanations on the origin of the vagus nerve somatosensory evoked potentials (VSEP).

Methods

We systematically search and critically appraise in PubMed, Web of Science, and Scielo databases the scientific reports publishing VSEP findings elicited by afferent electrical stimulation at the tragus region from individuals without brain disorders. Eligible studies published from January 2000 to April 2020 were extracted. The following information was identified from each article: number of participants; age; gender; stimulating/recording and grounding electrodes as well as stimulus side, intensity, duration, frequency, and polarity. Information about physiological parameters and neurobiological variables was also extracted. Representative vignettes with novel scalp responses induced by stimulating the tragus were also included to add support to our conclusions.

Results

140 healthy participants were identified from six selected reports. Mean age ranged from 24.3 to 61.5 years. Stimulating and recording aspects were miscellaneous among studies. Scalp responses marked as the VSEP were recorded in 76% of participants, and showed high variability, low validity and poor reproducibility. Age correlated with response latencies. There were not gender differences in scalp response parameters. Cardiovascular function was unaltered by tragus stimulation. Vignettes showed that the VSEP was scalp muscle responses.

Conclusion

VSEP did not fulfil evoked potential guidelines. VSEP corresponded to volume conduction propagating from muscles surrounding scalp recording sites.

中文翻译：

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完整大脑中的迷走神经体感诱发电位：证据状态和一些有代表性的小插曲

摘要

客观的

通过在人外耳的耳屏区域应用传入电刺激引起的头皮记录的诱发电位显示出不一致的结果。我们旨在解决不一致的发现和解释，并对迷走神经体感诱发电位 (VSEP) 的起源提出新的生理学解释。

方法

我们在 PubMed、Web of Science 和 Scielo 数据库中系统地搜索和批判性评估发表 VSEP 发现的科学报告，这些发现是由没有脑部疾病的个体在耳屏区域的传入电刺激引起的。提取了 2000 年 1 月至 2020 年 4 月发表的符合条件的研究。从每篇文章中确定了以下信息：参与者人数；年龄; 性别; 刺激/记录和接地电极以及刺激侧、强度、持续时间、频率和极性。还提取了有关生理参数和神经生物学变量的信息。还包括通过刺激耳屏引起的具有新颖头皮反应的代表性小插曲，以支持我们的结论。

结果

从六份选定的报告中确定了 140 名健康参与者。平均年龄介于 24.3 至 61.5 岁之间。研究中的刺激和记录方面是杂项。76% 的参与者记录了标记为 VSEP 的头皮反应，并表现出高变异性、低效度和差的可重复性。年龄与反应延迟相关。头皮反应参数没有性别差异。耳屏刺激未改变心血管功能。小插图显示 VSEP 是头皮肌肉反应。

结论

VSEP 不符合诱发电位指南。VSEP 对应于从头皮记录部位周围的肌肉传播的体积传导。