Authors: Ishita Marwaha¹; Prashanth Prabhu¹
¹All India Institute of Speech and Hearing (AIISH), Mysore
Background: Misophonia involves extreme aversive reactions to specific sounds, potentially reflecting altered central auditory gain. The loudness dependence of auditory evoked potentials (LDAEP) (N1–P2 amplitude slope) serves as an established biomarker of cortical serotonergic function and intensity-dependent loudness processing, but remains unexplored in the context of misophonia. We hypothesized steeper N1–P2 slopes and altered subjective loudness scaling, indicating enhanced cortical gain and compressed dynamic range.
Method: 20 adults (10 controls, 10 misophonia; normal hearing) participated. LDAEP was recorded using 1 kHz tones (40-80 dB nHL) via ER-3A inserts. Vertical montage: Cz/non-inverting, M1&M2/inverting, Fpz/ground. Primary outcome included N1–P2 amplitude slopes. Categorical loudness scaling was performed using a 7-point scale (ISO 2006). Welch’s independent t-tests compared groups, and post-hoc power analysis evaluated effect robustness.
Results: Misophonia demonstrated significantly steeper N1–P2 slopes (M=0.184 μV/dB) vs controls (M=0.129 μV/dB; p=0.008, d=1.79). Categorical loudness scaling revealed a trend towards shallower slopes in misophonia (M=0.072) vs controls (M=0.085; p=0.07, d=0.68). Post-hoc power exceeded 78% for the N1–P2 large effect, confirming that observed differences exceed chance expectation despite the modest sample.
Conclusion: Misophonia manifests enhanced objective cortical gain alongside compressed subjective loudness rating, suggesting dissociated central auditory processing with gain-compression mismatch. This finding positions N1–P2 LDAEP slope as a promising objective biomarker for misophonia diagnosis, though larger replication studies are needed to confirm robustness.
