The binaural interaction component in Rhesus Macaques (Macaca mulatta).

The binaural interaction component (BIC) is a sound-evoked electrophysiological signature of binaural processing in the auditory brainstem that has received attention as a potential biomarker for spatial hearing deficits. Yet the number of trials necessary to evoke the BIC, or its measurability, seems to vary across species: while it is easily measured in small rodents, it has proven to be highly variable and less reliably measured in humans. This has hindered its potential use as a diagnostic tool. Further measurements of the BIC across a wide range of species could help us better understand its origin and the possible reasons for the variation in its measurability. Statistical analysis on the function relating BIC DN1 amplitude and the interaural time difference has been performed in only a few small rodent species, thus is remains to be shown how the results apply to more taxonomically diverse mammals, and those with larger heads. To fill this gap we measured BICs in Rhesus Macaque. We show the overall behavior of the BIC is the same as in smaller rodents, suggesting that the brainstem circuit responsible for the BIC is conserved across a wider range of mammals. We suggest that differences in measurability are likely due to differences in head size.Significance StatementThis article reports measurements of the binaural interaction component (BIC) of the auditory brainstem response in Rhesus Macaques. Comparison with other species reveals that the behavior of the macaque BIC is similar, and, based on data available so far, statistically indistinguishable to previously measured small rodents, suggesting that the brainstem circuit that generates it is largely conserved across all rodents and primates. Differences in the measurability of the BIC are likely due to variation in head size rather than differences in the neuroanatomy.