Abstract
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.
Highlights
Responses of the human somatosensory system to a variety of stimuli have been studied extensively in research and are useful in clinical sensory testing [1]
Subjective ratings of sensations evoked by peripheral ultrasonic neurostimulation Ultrasound (US) can produce both mechanical and thermal bioeffects on tissues [26,27] depending on several factors including the acoustic frequency of US used, the duty cycle of waveforms, the types of transducers used, the peak and temporal-average intensities of US waveforms, the total energy delivered, and different US absorption coefficients for tissues [26,27]
One visual analog scales (VAS) assessed the intensity of a stimulus, while the other VAS assessed the thermal sensation generated by a stimulus
Summary
Responses of the human somatosensory system to a variety of stimuli have been studied extensively in research and are useful in clinical sensory testing [1]. Mechanical stimulation of somatosensory circuits can be achieved through simple punctate stimulation, the application of textured surfaces to the skin, and vibration These stimuli activate different mechanoreceptors of the skin and underlying tissues [2,3,4]. The brain responds to these various stimulus modalities by exhibiting somatosensory-evoked potentials (SEPs), contact heat-evoked potentials (CHEPs) and laser-evoked potentials (LEPs) depending on the stimulation approach used [1,5,6,7]. These evoked potentials (EPs) can exhibit unique spatial and temporal waveform morphologies arising from the different receptor populations and fiber tracts activated. Mechanical stimuli have been demonstrated to preferentially activate primary and secondary somatosensory cortices while thermal and noxious stimulation often activates additional areas including the cingulate and insular cortices [5,8,9,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
