Behavioral Auditory Function After Transection of Crossed Olivo-Cochlear Bundle in the Cat: I. Pure-tone Threshold and Perceptual Signal-to-noise Ratio

Abstract

The feline subjects were behaviorally conditioned to respond to pure tone signals at different frequencies based upon the avoidance conditioning procedure. After the transection of crossed olivo-cochlear bundle, the pure tone threshold (250–14 000 Hz) was not altered. Neither was any alteration found in the measurement of the perceptual signal-to-noise ratio at the levels of 30, 50, and 70 dB above the subjects' pure tone thresholds. Morphological confirmation of the brain stem and cochlear end organs demonstrated that proper surgical lesions had been made and there had been subsequent degeneration of the efferent nerve endings around the outer hair cells; especially in the basal coils. It is concluded, therefore, that the absence of the crossed olivo-coch-lear bundle has no effect on the behavioral measurement of pure tone thresholds and perceptual signal-to-noise ratio in the cat.