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Title: Investigation of ultrasonic neuro-stimulation effects in peripheral axons
Author: Wright, C. J.
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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Appreciation for the medical and research potential of ultrasound neuromodulation is growing rapidly, with potential applications in non-invasive treatment of neuro-degenerative disease and functional brain mapping spurring recent progress. A full understanding of the mechanical interaction of sound waves and neural tissue could allow tailor-made stimuli to produce different effects or specifically stimulate separate tissue types, adding great value to an already promising technique. Despite this worthy goal, little progress has been made in our understanding of the nature of the ultrasound-tissue interaction. The current study forms part of a long term goal to tackle this issue by isolating and characterising the effects of, and sensitivity to ultrasound for all the different structures found in nervous tissue. A simple, well characterised model of nervous transmission is therefore used along with a tightly controlled acoustic environment so that the characteristics of direct US stimulation effects can be investigated. Experiments are performed that demonstrate the capability of ultrasound to directly stimulate unmyelinted peripheral axons, characterise the stimulus response dynamics and determine the responsible ultrasonic force mechanism. A PCD, unimpeded ultrasound path and wavelet acoustic analysis techniques are used to detect different modes of cavitation with high sensitivity which are then tested for correlation to nerve responses. In the present case, direct ultrasound stimulation of peripheral axonal tissue is found to require either stable or inertial cavitation. The lowest intensity at which stimulation is observed is 25 W/cm2, similar to previous neuromodulatory thresholds found in peripheral nerves. This study therefore represents a significant advance in our understanding of the mechanisms behind the ultrasound neurostimulation phenomenon.
Supervisor: Saffari, N. ; Rothwell, J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available