Reversible Effects of Ultrasound on Spinal Reflexes

Abstract

Introduction This investigation is one of 3 studies^1,2 undertaken so explore the potentialities of high-intensity ultrasound in experimental neurology. Recently there has been increasing interest in this field. Techniques have been developed for producing lesions of constant size and shape at selected sites in the central nervous system.^3-6 Less attention has been paid to the effects of ultrasound on functioning neural circuits. Concurrent studies on the peripheral nerves of frogs¹ and cats² show that focused ultrasound will block axonal conduction reversibly or irreversibly, depending upon dosage. The smallest axons, the delta fibers and the C fibers, are most sensitive to irradiation. In these experiments a segment of the cat's spinal cord was irradiated with ultrasound; the effects of the irradiation on the transmission of reflexes through that segment were followed oscillographically, and histological studies were carried out on the irradiated tissue. Spinal reflexes, elicited and recorded