Dr. Young’s research group studies synapses – the highly specialized contact points in the brain where neurons pass electrical and chemical signals to one another. The human brain consists of approximately 100 billion neurons and makes ~10,000 synaptic contacts per neuron.
Encoding the onset and modulation of sound at the initial stages of auditory processing requires that synapses respond to rapid and large fluctuations in firing rates over variable timescales, superimposed on a broad range of spontaneous activity. Chemical synaptic transmission relies on a limited number of fusion competent synaptic vesicles (SVs) in the presynaptic terminal, termed the readily releasable pool (RRP); thus sound encoding places great demands on the temporal dynamics of SV release and recycling. Critical to the binaural processing of sound is the calyx of Held, a giant axosomatic glutamatergic presynaptic terminal that arises from the globular bushy cells (GBC) in the cochlear nucleus. The calyx preserves temporal fidelity of the afferent spike train in its patterns of SV release to drive postsynaptic spiking in the principal neurons of the medial nucleus of the trapezoid body (MNTB). The MNTB relays these activity patterns as inhibitory inputs to key binaural cell groups. Due to its experimental accessibility the calyx provides unparalleled opportunities to gain insights into presynaptic mechanisms that support the early stages of auditory processing.