Time and intensity coding at the hair cell's ribbon synapse


  • Paul Albert Fuchs

    1. The Cochlear Neurotransmission Laboratory, Center for Hearing and Balance, Department of Otolaryngology – Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21286, USA
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  • This report was presented at The Journal of Physiology Symposium on The Senses, San Diego, CA, USA, 22 October 2004. It was commissioned by the Editorial Board and reflects the views of the authors.

Corresponding author P. A. Fuchs: 521 Traylor Building, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205-2195, USA. Email: pfuchs@jhmi.edu


The activity of individual afferent neurones in the mammalian cochlea can be driven by neurotransmitter released from a single synaptic ribbon in a single inner hair cell. Thus, a ribbon synapse must be able to transmit all the information on sound frequency, intensity and timing carried centrally. This task is made still more demanding by the process of binaural sound localization that utilizes separate computations of time and intensity, with temporal resolution as fine as 10 μs in central nuclei. These computations may rely in part on the fact that the response phase (at the characteristic frequency) of individual afferent neurones is invariant with intensity. Somehow, the ribbon synapse can provide stronger synaptic drive to signal varying intensity, without accompanying changes in transmission time that ordinarily occur during chemical neurotransmission. Recent ultrastructural and functional studies suggest features of the ribbon that may underlie these capabilities.