Strength of the efferent olivocochlear system modifies the activity of a central auditory nuclei

DI GUILMI, MN, GÓMEZ-CASATI, ME, BOERO, LE AND ELGOYHEN AB

Mar del Plata

Congreso; XXXI Congreso Anual de la Sociedad Argentina de Investigación en Neurociencia; 2017

Sociedad Argentina de Investigaciones en Neurociencia

The auditory system in many mammals is immature at birth but precisely organized in adults. Spontaneous activity in the inner ear comes into play to guide this process. This spontaneous activity is modulated by an efferent pathway that descends from the brain. In this work, we used a mouse model with enhanced medial efferent activity (Chrna9L9?T, KI) to understand the role of the olivocochlear efferent system in the correct establishment of auditory circuits. Wave III of auditory brainstem responses (which represents synchronized activity of synapses within the Superior Olivary Complex) was smaller in the KI suggesting a central dysfunction. In order to analyze this functional observation, we studied the underlying mechanism on brain slices containing the medial nucleus of the trapezoid body (MNTB) where neurons are topographically organized along a medio-lateral axis. Various MNTB physiological properties with a tonotopic organization in WT mice were abolished in the KI. Additionally, slice recordings evidenced synaptic alterations on the MNTB in agreement with the ABR recordings. Our results suggest that medial efferent activity before hearing onset is involved in the refinement of the tonotopic map of the MNTB.