Small Localized Ultrasonic Lesions in the White and Gray Matter of the Cat Brain

The work reported here is a continuation of the study in progress at this laboratory of the effects of accurately controlled doses of ultrasound on the tissue of the central nervous system. Previous publications * were concerned with the production and study of ultrasonically produced lesions in white matter. It was reported that selective lesions of almost any desired shape can be produced at any depth in the brain without affecting any intervening tissue by positioning the focus of a beam of high-frequency sound in the region to be affected. The previous work was restricted to the study of relatively large white-matter lesions produced by irradiating the tissue in a number of positions in an appropriately chosen overlapping pattern of spots. This paper is concerned with the histological study of small lesions produced by irradiating the tissue in a single spot with focused beams. The dosage conditions necessary for producing selective