Giant synapses in the central auditory system

Abstract

Giant synapses occur in four nuclei of the auditory brainstem. They are characterized by numerous active zones concentrated on the soma of the postsynaptic neuron and by rapid postsynaptic currents. At these sites, in the ventral cochlear nucleus, the medial and lateral nucleus of the trapezoid body and the ventral nucleus of the lateral lemniscus, faithful preservation of the temporal relation of action potentials to the sound - intercellular precision - is of uttermost importance for neuronal function. The precision of action potential transfer is supported by the largely unimodal integration and by the homogeneity of the single postsynaptic compartment. Due to the much more rapid time constant of the synaptic currents compared to the membrane time constant, membrane capacitance dominates postsynaptic integration, enhancing precision of action potential generation. Taken together, the properties of these giant synapses reduce the temporal jitter of the transmission of information in these auditory circuits.