Electrogenic NMDA receptor signaling enhances binaural responses in the adult brainstem

Abstract

In sensory systems the neuronal representation of external stimuli is enhanced along the sensory pathway. In the auditory system, strong enhancement of binaural information takes place between the brainstem and the midbrain, however the underlying cellular mechanisms are unknown. Here we investigated the transformation of binaural information in the dorsal nucleus of the lateral lemniscus (DNLL), a nucleus that connects the binaural nuclei in the brainstem and the inferior colliculus in the midbrain. We used in vitro and in vivo electrophysiology in adult Mongolian gerbils to show that NMDARs play a critical role in neuronal encoding of stimulus properties in the DNLL. While NMDARs increase firing rates, the timing and the accuracy of the neuronal responses remain unchanged. NMDAR mediated excitation increases the information about the acoustic stimulus. Taken together, our results show that NMDARs in the DNLL enhance the auditory information content in adult mammal brainstem.

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