Joshua Goldwyn: Dynamical characteristics of neural coincidence detection in auditory brainstem neurons

Neurons that convey sound information to the brain must process and transmit temporally precise signals.  One physical cue for sound source localization is the interaural time difference (ITD) created by the differences in arrival times of sounds at the two ears.  ITDs are on the order of microseconds, and yet specialized neurons in the auditory brainstem are sensitive to these small timing differences.  Using biophysically-based computational models (Hodgkin-Huxley like models, and similar) of neurons in the auditory brainstem, we identify and isolate dynamical and structural features that enable these neurons to respond with to synaptic inputs with submillisecond precision.  I will describe my work modeling distinct cell types in the mammalian brainstem, as well neurons that perform similar sound localization computations in the brainstem of the barn owl.  The structural profile of how the soma and axon regions of neurons connect, as well as dynamical features of their spiking activity, contribute to the remarkable temporal precision of these cells.  We have also investigated how the structural and dynamical specializations of these neurons may be degraded during periods of hearing loss.  During periods of sound deprivation (as a model for hearing loss), the size and electrophysiology of auditory brainstem neurons can change in-line with homeostatic principles (to increase excitability and activity, in the absence of typical levels of synaptic inputs).    By modeling neural responses to cochlear implant stimulation, we show how such pathological changes to auditory brainstem neurons may hinder sound source localization for users of cochlear implants.