Functional Development of Principal Neurons in the Anteroventral Cochlear Nucleus Extends Beyond Hearing Onset

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Developmental Neuroscience

Background:

• Auditory information is processed by cochlear hair cells and auditory nerve fibers.
• Bushy cells (BCs) and stellate cells (SCs) in the cochlear nucleus process distinct sound features.
• Understanding in vivo functional development of these neurons is crucial for mouse models.

Purpose of the Study:

• To characterize the maturation of spontaneous and acoustically evoked activity in BCs and SCs.
• To investigate the developmental timeline of auditory processing from hearing onset to young adulthood in mice.
• To compare the maturation processes of BCs and SCs in the auditory pathway.

Main Methods:

• Single-unit juxtacellular recordings were performed in anesthetized CBA/J mice.
• Recordings spanned from hearing onset (P12) to young adulthood (P30).
• Functional properties including hearing sensitivity, characteristic frequency, firing rates, dynamic range, temporal response, and latency were assessed.

Main Results:

• Hearing sensitivity and characteristic frequency (CF) range were largely adult-like by P14 in both BCs and SCs.
• BCs showed further maturation of physiological features up to P18, including firing rate and temporal coding.
• SCs exhibited prolonged development of excitatory responses up to P30, with acoustically evoked inhibition present from hearing onset.

Conclusions:

• Maturation of auditory processing in BC and SC pathways involves distinct mechanisms at the first central synapses.
• The development of auditory processing in these parallel streams may be influenced by early auditory experience.
• Distinct developmental trajectories of BCs and SCs contribute to specialized sound feature processing in the auditory system.