Measurement of Focused Ultrasound Neural Stimulation; Somatosensory Evoked Potential at Two Separate Skin Temperatures

Focused ultrasound stimulation (FUS) can induce painful sensations that are measurable as somatosensory evoked potentials [1]. Here we compare FUS neural stimulation to electrical neural stimulation at two different subdermal skin temperatures (baseline ambient temperature at 33 °C and cooled skin at 15.4 °C), over four different pulse duration (400, 450, 500, and 550 ms) on-times. FUS somatosensory evoked potential (USEP) characteristics peaks (P1, N2, P2) obtained at ambient and cooled skin temperatures were not significantly different from each other in latency or amplitude. We observed that at both ambient and cooled skin temperatures resultant evoked potential was time synced to FUS offset and not a specific high temperature threshold. In aggregate, these pilot data suggest dermal FUS neural stimulation is a result of mechanical impacts activating subdermal skin nociceptors that is less dependent on tissue heating.