Small dendritic synapses enhance temporal coding in a model of cochlear nucleus bushy cells

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Computational Neuroscience

Background:

• Spherical bushy cells (SBCs) in the anteroventral cochlear nucleus are crucial for auditory processing.
• SBCs receive powerful axosomatic inputs and weaker dendritic inputs from the auditory nerve.
• The precise function of these small dendritic inputs remains largely unknown.

Purpose of the Study:

• To investigate the functional role of small, excitatory dendritic inputs to SBCs.
• To test the hypothesis that dendritic inputs enhance temporal precision through interaction with axosomatic inputs.
• To explore the biophysical mechanisms underlying the influence of dendritic inputs on SBCs.

Main Methods:

• Development of a compartment model of SBCs with stylized and realistic 3-D dendritic structures.
• Simulation of phase-locked dendritic inputs to the SBC model.
• Analysis of model responses to varying dendritic input parameters and frequencies.

Main Results:

• Dendritic inputs caused tonic depolarization and modulated SBC membrane potential at the stimulus frequency.
• Subthreshold dendritic inputs increased SBC excitability and phase-dependently enhanced the efficacy of axosomatic inputs.
• Improved response rate, entrainment at low frequencies, and temporal precision at and above characteristic frequencies were observed.

Conclusions:

• Small excitatory dendritic inputs play a direct role in auditory processing by modulating main inputs.
• These dendritic inputs are a plausible mechanism for enhancing temporal precision and fidelity in central auditory neurons.
• The study provides functional insights into the peculiar morphology of the bushy dendrite.