Further Electrophysiological Observations on Auditory Masking and Fatigue

Electrical responses to supra-threshold acoustic clicks are easily observed at the two extreme stations of the auditory nervous system of anesthetized cats: the round window and the auditory cortex. The neural components of the round window response and the cortical potentials have been shown to be particularly sensitive, amplitudewise, to masking noises and to previous exposure to loud sounds. The effects of repeated exposures and the effects of the intensity and duration parameters for given exposures have been investigated. We have also collected data regarding central factors in masking and fatigue. Present results indicate: (1) that the cortical response to supra-threshold clicks delivered to the left ear remains essentially unaffected after the right ear has been exposed to loud sounds; (2) that the cortical response to a click delivered to the left ear is unaffected by a masking noise delivered to the right ear, even if the noise is sufficient to reduce (mask) the neural response to a right ear click stimulus. These results are valid only as long as there is no appreciable acoustic leakage from ear to ear.