Epidermal Electrode Technology for Detecting Ultrasonic Perturbation of Sensory Brain Activity
Stanley Huang, Jonathan A. N. Fisher, Meijun Ye, Yun-Soung Kim, Rui Ma, Marjan Nabili, Victor Krauthamer, Matthew R. Myers, Todd P. Coleman, Cristin G. Welle
IEEE Transactions on Biomedical Engineering 2018 · 10.1109/tbme.2017.2713647
Abstract
Objective We aim to demonstrate the in vivo capability of a wearable sensor technology to detect localized perturbations of sensory-evoked brain activity. Methods Cortical somatosensory evoked potentials (SSEPs) were recorded in mice via wearable, flexible epidermal electrode arrays. We then utilized the sensors to explore the effects of transcranial focused ultrasound, which noninvasively induced neural perturbation. SSEPs recorded with flexible epidermal sensors were quantified and benchmarked against those recorded with invasive epidural electrodes. Results We found that cortical SSEPs recorded by flexible epidermal sensors were stimulus frequency dependent. Immediately following controlled, focal ultrasound perturbation, the sensors detected significant SSEP modulation, which consisted of dynamic amplitude decreases and altered stimulus-frequency dependence. These modifications were also dependent on the ultrasound perturbation dosage. The effects were consistent with those recorded with invasive electrodes, albeit with roughly one order of magnitude lower signal-to-noise ratio. Conclusion We found that flexible epidermal sensors reported multiple SSEP parameters that were sensitive to focused ultrasound. This work therefore 1) establishes that epidermal electrodes are appropriate for monitoring the integrity of major CNS functionalities through SSEP; and 2) leveraged this technology to explore ultrasound-induced neuromodulation. The sensor technology is well suited for this application because the sensor electrical properties are uninfluenced by direct exposure to ultrasound irradiation. Significance The sensors and experimental paradigm we present involve standard, safe clinical neurological assessment methods and are thus applicable to a wide range of future translational studies in humans with any manner of health condition.
Abstract via europepmc.
Exposures
Exposure 1: Focused ultrasound perturbation of frontal lobe (40, 100 or 300 pulses)
Target: frontal lobe — “the frontal lobe”
Device: Sonic Concepts · Sonic Concepts · H102 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 1,100 | ✓✓✓ |
| Pulse duration (ms) | 10 | ✓✓✓ |
| Pulse repetition frequency (Hz) | not reported | ⚑ |
| Duty cycle (%) | not reported | |
| Sonication duration (s) | not reported | ⚑ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | simulationsingle value | |
| In-situ pressure (kPa) | not reported | ⚑ |
| In-situ Isppa (W/cm²) | 85 | ✓✓✓⚑ |
| In-situ Ispta (W/cm²) | not reported | |
| Pressure, domain unspecified (kPa) | 4,000 | ✓✓✓⚑ |
Pulse train of 1.1 MHz sinusoidal pulses, each of duration 10 ms, followed by an off time of 200 ms; 40, 100 or 300 pulses per animal.
Flags from extraction
exposures[0].timing.pulse_repetition_frequency_hz— PRF and duty cycle not stated; only 10 ms pulses with a 200 ms off time.exposures[0].timing.sonication_duration_s— Only pulse counts (40/100/300) given; no total duration.exposures[0].unspecified_domain.pressure_kpa— 19 MPa peak positive pressure at the focus (converted to kPa); domain (water vs head) not clearly stated.exposures[0].in_situ.isppa_w_cm2— Intensity of about 85 W/cm2 computed from simulated RMS pressure 1.6 MPa by plane-wave relation, just inside the skull; paper does not label it as pulse-average, and the figure does not obviously match 1.6 MPa RMS.exposures[0].in_situ.pressure_kpa— Simulated RMS pressure of 1.6 MPa given, not a peak pressure, so not entered.