Low Intensity Noise Exposure Enhanced Auditory Loudness and Temporal Processing by Increasing Excitability of DCN

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Sensory Processing

Background:

• Sound stimulation is a common therapeutic approach for tinnitus and hyperacusis.
• Long-term noise exposure is known to alter synaptic and firing properties in the central auditory system.
• The perceptual effects of prolonged low-intensity sound exposure remain unclear.

Purpose of the Study:

• To investigate the impact of moderate-level noise exposure on auditory loudness and temporal processing.
• To evaluate changes in neural activity within the central auditory pathway using c-Fos staining.
• To determine if moderate noise exposure affects auditory brainstem response (ABR) and acoustic startle response (ASR).

Main Methods:

• CBA/CaJ mice were exposed to 83 dB SPL noise for 8 hours daily over two weeks.
• Auditory brainstem response (ABR) was measured to assess hearing thresholds.
• Acoustic startle response (ASR) and gap-induced prepulse inhibition (gap-PPI) were evaluated.
• C-Fos staining was employed to map neural activity in the central auditory pathway, including the dorsal cochlear nucleus (DCN) and caudal pontine reticular nucleus (PnC).

Main Results:

• Two weeks of 83 dB SPL noise exposure did not result in a persistent threshold shift in ABR.
• Noise exposure significantly enhanced the acoustic startle response (ASR) and gap-induced prepulse inhibition (gap-PPI).
• Increased c-Fos expression was observed in the DCN and PnC, indicating heightened neural activity in these auditory brainstem regions.

Conclusions:

• Moderate-level noise exposure can alter auditory temporal acuity without causing a permanent hearing threshold shift.
• The observed changes in ASR and gap-PPI suggest enhanced temporal processing.
• Noise stimulation appears to increase the excitability of auditory brainstem neurons, potentially underlying the altered acoustic temporal processing.