Modeling cellular mechanisms underlying representations of temporal modulation in the auditory midbrain and thalamus

In animals and humans, temporal processing of acoustic features is critical for perception of species-specific sounds and speech. Time varying sound features are often represented in the early auditory pathway as stimulus-synchronized patterns of neural activity. These representations undergo transformation as they pass from the inferior colliculus (IC) to auditory cortex via the medial geniculate body (MGB). IC responses preserve their synchronized inputs but show much greater firing rate modulation than many of their inputs. How the inputs to IC converge to generate tuned rate and temporal coded response patterns is poorly understood. In the MGB, two different responses are observed: Stimulus-synchronized responses faithfully preserve the temporal coding from its afferent inputs, and Non-synchronized responses, which are not phase locked to in the inputs, represent changes in temporal modulation by a rate code. The cellular mechanisms that produce these segregated responses are also poorly understood. Single compartment neuron models of the IC and MGB were created using MATLAB and NEURON software. The most commonly observed IC response subtypes were recreated, enabling dissociation of inherited response properties from those that were generated in IC (Rabang et al., 2012). The MGB model investigated the role of two differing populations of excitatory inputs, feedforward inhibition, and synaptic plasticity on the generation of either synchronized or non-synchronized responses (Rabang and Bartlett, 2011). Patch clamp recordings from MGB neurons verified synaptic model parameters. Both models recreated in vivo responses and made predictions about the role of inhibition in normal hearing and age-related hearing loss