Virginia Tech Carilion Research Institute and School of Biomedical Engineering and Sciences, Virginia Tech, Roanoke, Virginia, United States of America.
PLoS One. 2012;7(12):e51177. doi: 10.1371/journal.pone.0051177. Epub 2012 Dec 4.
Peripheral somatosensory circuits are known to respond to diverse stimulus modalities. The energy modalities capable of eliciting somatosensory responses traditionally belong to mechanical, thermal, electromagnetic, and photonic domains. Ultrasound (US) applied to the periphery has also been reported to evoke diverse somatosensations. These observations however have been based primarily on subjective reports and lack neurophysiological descriptions. To investigate the effects of peripherally applied US on human somatosensory brain circuit activity we recorded evoked potentials using electroencephalography and conducted functional magnetic resonance imaging of blood oxygen level-dependent (BOLD) responses to fingertip stimulation with pulsed US. We found a pulsed US waveform designed to elicit a mild vibration sensation reliably triggered evoked potentials having distinct waveform morphologies including a large double-peaked vertex potential. Fingertip stimulation with this pulsed US waveform also led to the appearance of BOLD signals in brain regions responsible for somatosensory discrimination including the primary somatosensory cortex and parietal operculum, as well as brain regions involved in hierarchical somatosensory processing, such as the insula, anterior middle cingulate cortex, and supramarginal gyrus. By changing the energy profile of the pulsed US stimulus waveform we observed pulsed US can differentially activate somatosensory circuits and alter subjective reports that are concomitant with changes in evoked potential morphology and BOLD response patterns. Based on these observations we conclude pulsed US can functionally stimulate different somatosensory fibers and receptors, which may permit new approaches to the study and diagnosis of peripheral nerve injury, dysfunction, and disease.
周围感觉回路已知对不同的刺激模式有反应。传统上能够引起感觉反应的能量模式属于机械、热、电磁和光子领域。也有报道称，应用于外周的超声波（US）能够引起不同的感觉。然而，这些观察结果主要基于主观报告，缺乏神经生理学描述。为了研究外周应用 US 对人类感觉大脑回路活动的影响，我们使用脑电图记录诱发电位，并进行功能磁共振成像（fMRI），以记录脉冲 US 刺激指尖时血氧水平依赖（BOLD）反应。我们发现，设计用于引起轻微振动感觉的脉冲 US 波形可靠地触发了具有明显波形形态的诱发电位，包括一个大的双峰顶点电位。用这种脉冲 US 波形刺激指尖也会导致大脑中与感觉辨别相关的区域出现 BOLD 信号，包括初级感觉皮层和顶叶岛盖，以及涉及分层感觉处理的区域，如脑岛、前中扣带皮层和缘上回。通过改变脉冲 US 刺激波形的能量分布，我们观察到脉冲 US 可以有区别地激活感觉回路，并改变伴随诱发电位形态和 BOLD 反应模式变化的主观报告。基于这些观察结果，我们得出结论，脉冲 US 可以功能性地刺激不同的感觉纤维和感受器，这可能为外周神经损伤、功能障碍和疾病的研究和诊断提供新的方法。
