Date of Completion

12-26-2017

Embargo Period

12-26-2017

Advisors

Dr. Bin Feng, Dr. Sabato Santaniello, Dr. Martin Han, Dr. Patrick D. Kumavor

Field of Study

Biomedical Engineering

Degree

Master of Science

Open Access

Open Access

Abstract

Ultrasound as a widely used imaging means for medical diagnosis has drawn growing interests as a potential noninvasive neuromodulation strategy. Focused pulsed ultrasound effectively modulates neural encoding and transmission functions especially in the peripheral nervous system (PNS) with unclear mechanism of action, which is further confounded by contradictory experimental outcomes. Lack of convincing experimental methods has hindered our mechanistic understanding of ultrasonic PNS neuromodulation. To address that, we developed a novel in vitro set up to achieve simultaneous single-unit recordings from individual mouse sciatic nerve axon and systematically studied the effect of focused pulsed ultrasound (FPUS) on action potential transmission in individual axons. Unlike previous results that were derived from bulk recordings of compound action potentials (CAP) or evoked muscle forces, our single-unit recordings afford superior spatial and temporal resolution to reveal the subtle but consistent effect of ultrasonic neuromodulation. Our results indicate that, 1) FPUS does not evoke action potentials in mouse sciatic nerve directly at all the tested intensities (spatial peak temporal average intensity, ISPTA of 0.91 to 28.2 W/cm2); 2) FPUS increases the nerve conduction velocity (CV) in both fast-conducting A- and slow-conducting C- type axons with effect more pronounced at increased stimulus duration and intensity; and 3) Effect of increased CV is reversible and cannot be attributed to the change of local temperature. Our results fortify the assumptions of non-thermal mechanisms underlying ultrasonic neuromodulation with low-intensity FPUS and provide with an accurate experimental basis, for the validation of existing hypotheses and models (e.g., NICE, flexoelectricity, soliton) and discovery of any new theorem.

Major Advisor

Dr. Bin Feng

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