Responses elicited from medial superior olivary neurons by stimuli associated with binaural masking and unmasking.

The responses of binaural neurons of the medial superior olive were measured as a function of interaural temporal differences for tones and as a function of signal-to-noise ratio under homophasic and antiphasic masking conditions. The degree of neural response synchrony to the frequency of the signal was related to the degree of behavioral detectability of the signal in the homophasic, but not the antiphasic masking condition. For the antiphasic condition, a decrease in discharge rate resulted from the addition of the signal to the noise, similar to the decrease which occurred when interaural temporal differences were introduced in the tonal stimuli. The results are compatible with a model in which interaural temporal-difference information arriving over monaural afferents in the form of synchronized impulses is mapped into a place code by a neural coincidence-detection device. Several differences were noted between the responses to tones found in the present experiment and those reported by others. These differences were attributed mainly to differences among the experimental procedures in use among the various reporting laboratories.