Right-left correlation in guinea pig ears after noise exposure

Area of Science:

• Audiology
• Experimental Otolaryngology
• Neuroscience

Background:

• Noise-induced hearing loss is a significant occupational and environmental health concern.
• Understanding the variability of hearing threshold shifts within an animal model is crucial for experimental design.

Purpose of the Study:

• To determine if experimental units in noise-exposure studies should be considered individual ears or whole animals.
• To assess the correlation of permanent threshold shifts between the right and left ears in guinea pigs exposed to noise.

Main Methods:

• Action potential (N1) thresholds were measured at 14 frequencies in both ears of 53 groups of 5 noise-exposed guinea pigs.
• Permanent threshold shifts were analyzed, comparing right and left ear measurements.
• Correlation coefficients were calculated to assess the relationship between ear measurements, with comparisons between impact and continuous noise exposure.

Main Results:

• A high average right-left correlation coefficient of approximately 0.79 was observed, irrespective of noise energy.
• The informative value of measuring the second ear was only 11% of the first, due to the strong correlation.
• Correlation was significantly higher for impact noise compared to continuous noise.
• No correlation was found between skin pigmentation and threshold elevation.

Conclusions:

• Experimental material in noise-exposed animals can be effectively treated as 'ears' due to high interaural correlation.
• The high correlation simplifies experimental design and reduces the need for bilateral measurements in similar studies.
• Impact noise leads to more correlated threshold shifts between ears than continuous noise.