Dynamic changes in level influence spatial coding in the lateral superior olive.

It is well established that the responses of binaural auditory neurons can adapt and change dramatically depending on the nature of a preceding sound. Examples of how the effects of ensuing stimuli play a functional role in auditory processing include motion sensitivity and precedence-like effects. To date, these types of effects have been documented at the level of the midbrain and above. Little is known about sensitivity to ensuing stimuli below in the superior olivary nuclei where binaural response properties are first established. Here we report on single cell responses in the gerbil lateral superior olive, the initial site where sensitivity to interaural level differences is established. In contrast to our expectations we found a robust sensitivity to ensuing stimuli. The majority of the cells we tested (86%), showed substantial suppression and/or enhancement to a designated target stimulus, depending on the nature of a preceding stimulus. Hence, sensitivity to ensuing stimuli is already established at the first synaptic station of binaural processing.