A Closed-Loop Gain-Control Feedback Model For The Medial Efferent System Of The Descending Auditory Pathway

Existing auditory system models focus on the ascending path from the cochlea to the midbrain and auditory cortex. However, there exist several feedback paths connecting different auditory pathway stages from the auditory cortex to the cochlea, referred to as the efferent system. We have implemented a dynamic, closed-loop gain-control system into an existing auditory model to simulate parts of the efferent system. Inputs to this control system are auditory nerve (AN) and midbrain spike rates that encode stimulus level and AN fluctuation patterns, respectively. Data from a previous physiological study shows that midbrain cells with band-enhanced modulation transfer functions have rates that increase over time in response to amplitude-modulated stimuli. This trend does not occur in a model without efferent pathways. We adjusted parameters of the model with efferent control paths so that it could simulate the increasing midbrain rate with the same time constant (~140ms) as physiological data.