Fig. 3: Transient hearing loss during adolescence impairs amplitude modulation (AM) depth detection in adulthood.

a Psychometric functions on the first day of perceptual testing for control (Ctrl, n = 12) and hearing loss (HL, n = 14) animals. Threshold was defined as the depth at which d′ = 1 (dotted line). AM depths are presented on a dB scale (re: 100% depth), where 0 dB corresponds to 100% modulation, and decreasing values indicate smaller depths (e.g., see gray depth stimuli visualized below x-axes). Circle indicates the average group detection threshold. b HL animals display significantly poorer AM detection thresholds than controls on the first day of testing (Ctrl: −11 ± 0.5, HL: −8 ± 0.7 dB re: 100%; p = 0.007). The AM detection deficit for HL animals persisted across 10 consecutive testing days. An analysis of covariance (ANCOVA, two-way) revealed the effect of HL alone to be significant (p = 7.6 × 10⁻¹²). Filled circles and lines indicate the group mean ± SEM. Open circles indicate individual data points for the first, middle, and last psychometric testing session to highlight between-subject variability between control and adolescent HL animals. c Perceptual improvement (initial subtracted from final threshold) as a function of initial threshold. Values above the dotted line indicate an improvement in thresholds, whereas values below indicate a worsening of thresholds. Dotted lines indicate fitted linear regressions (R2 = 0.3–34). The slopes (m) of the regression fits were not significantly different from one another (p = 0.8, ANCOVA), whereas the y-axis intercepts were significantly different indicating the average amount of improvement was lower in adolescent-HL animals (p < 0.0001). d The mean improvement from the initial to the final session for each group. Bars and associated error indicate group mean ± SEM. Control animals (n = 12) improved significantly more than transient HL animals (n = 14; ANCOVA, two-way; p = 0.018).