Noise trauma induced plastic changes in brain regions outside the classical auditory pathway

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Sensory Processing

Background:

• Intense noise exposure effects on the classical auditory pathway are well-studied.
• Limited research exists on noise-induced hearing loss impacts on non-classical auditory brain regions, including the lateral amygdala (LA) and striatum (Str).

Purpose of the Study:

• To investigate and compare noise-induced changes in spontaneous and tone-evoked neural responses in the rat LA and striatum with those in the auditory cortex (AC).
• To understand the functional consequences of noise trauma on neural processing in these brain areas.

Main Methods:

• Rats were exposed to high-frequency octave band noise (10-20 kHz) or narrow band noise (16-20 kHz).
• Spontaneous and tone-evoked responses from multiunit clusters (MUC) in the LA, Str, and AC were recorded and analyzed.
• Neural activity was assessed for changes in firing rates and temporal patterns.

Main Results:

• High-frequency noise exposure caused permanent threshold shifts at high frequencies.
• While auditory cortex (AC) showed elevated spontaneous discharge rates (SR), LA and Str exhibited only slight increases in SR.
• Tone-evoked firing rates were altered in a frequency- and time-dependent manner across all studied brain regions, with significant changes observed in the LA and AC, and generally decreased rates in the Str.
• Temporal firing patterns shifted, becoming sharper and more delayed in the LA, broader in the AC, and more phasic in the Str.

Conclusions:

• High-frequency noise-induced hearing loss significantly alters neural activity in non-classical auditory areas (LA, Str) and the AC.
• Observed changes in low-frequency neural responses and temporal patterns may underlie perceptual alterations like hyperacusis and affect temporal processing.
• This study highlights the broader impact of noise trauma beyond the classical auditory pathway.