Laser interferometric measurements of basilar membrane vibrations in cats using a round window approach

Our earlier basilar membrane measurements in cats were made through a hole in the cochlear wall. Drilling the hole invariably produced extensive cochlear damage even when the drills were designed to be extremely quiet. Mechanical tuning curves obtained in these damaged cochleas agree closely in shape with those shown by Evans and Wilson [Science 190, 1218–1222 (1975)]. A round window approach was adopted to eliminate drilling. Cochleas were opened without producing any bleeding by the use of a microcautery. Round window cochlear microphonics and tone pip N1 responses showed that the damage produced to the cochlea was reduced to a minimum. Basilar membrane measurements in these cochleas will be shown.