Both crossed and uncrossed efferent pathways protect the cochlea from loud sound-induced TTSs in nondamaging noise backgrounds that can exacerbate the sound-induced TTS
| Comparison groups/treatments3-a | ANOVAF and p values (Interaction = group × frequency interaction) | t test type3-b and df3-c | Frequency range with significant differences3-d and parameters of significance | |
|---|---|---|---|---|
| A. In ears with non-functional efferent pathways, noise backgrounds exacerbate loud tone-induced TTS, depending on noise intensity | ||||
| Silence 3 OC− | Noise 1 OC− | Group F= 0.33; p = 0.59 | ||
| (noise = 40 dB SPL) | InteractionF = 0.74; p = 0.76 | |||
| Silence 3 OC− | Noise 2 OC− | Group F = 131, p < 0.001 | Two-tail, df = 9 | 12, 13, 16–28 kHz; t always > 2.5; p generally < 0.005 |
| (noise = 60 dB SPL) | Interaction F = 8.02; p < 0.001 | |||
| Silence 3 OC− | Noise 3 OC− | Group F = 22.69; p < 0.001 | Two-tail, df = 8 | 12, 13, 16–28 kHz;t always > 2.5; p generally < 0.01 |
| (noise = 80 dB SPL) | Interaction F = 4.92;p < 0.001 | |||
| Noise 1 OC− | Noise 2 OC− | GroupF = 104.3; p < 0.001 | One-tail, df = 8 | 13, 16–28 kHz; t always > 2.3; p generally < 0.005 |
| (noise = 40 dB SPL) | (noise = 60 dB SPL) | InteractionF = 4.37; p < 0.001 | ||
| Noise 2 OC− | Noise 3 OC− | Group F = 5.91; p < 0.05 | One-tail, df = 11 | 10, 22–28 kHz; t always > 1.9; p < 0.05 |
| (noise = 60 dB SPL) | (noise = 80 dB SPL) | Interaction F = 1.73; p < 0.05 | ||
| B. In efferent-intact ears, noise backgrounds do not exacerbate the TTS caused by a loud tone | ||||
| Silence 3 OC+ | Noise 1 OC+ | Group F = 0.33; p = 0.59 | ||
| (noise = 40 dB SPL) | Interaction F = 0.74; p = 0.74 | |||
| Silence 3 OC+ | Noise 2 OC+ | Group F = 1.297;p = 0.28 | ||
| (noise = 60 dB SPL) | InteractionF = 0.99; p = 0.47 | |||
| Silence 3 OC+ | Noise 3 OC+ | Group F = 0.49; p = 0.5 | ||
| (noise = 80 dB SPL) | Interaction F = 0.403; p = 0.4 | |||
| C. The cochlear protection from loud sound-induced TTS in noise backgrounds is attributable to both crossed and uncrossed efferent pathways | ||||
| Noise 4 (COC−) | Noise 3 OC− | Group F = 34.22; p < 0.001 | One-tail, df = 14 | 9–28 kHz;t always > 2.04; p generally < 0.005 |
| (noise = 80 dB SPL) | (noise = 80 dB SPL) | Interaction F = 8.1;p < 0.001 | ||
| Noise 4 (COC−) | Noise 3 OC+ | Group F = 7.02; p < 0.02 | One-tail df = 12 | 12–18 kHz; t always > 2.1; p always < 0.05 |
| (noise = 80 dB SPL) | (noise = 80 dB SPL) | InteractionF = 2.08; p < 0.01 | ||
| Noise 5 COC− | Noise 5 OC+ | Group F = 1093; p < 0.001 | One-tail, df = 4 | 9–28 kHz; t always > 2.7;p generally < 0.0005 |
| (noise = 80 dB SPL) | (noise = 80 dB SPL) | Interaction F = 25.44; p < 0.001 | ||
↵F3-a All Noise groups were tested binaurally with the loud tone in a noise background. OC+ = all olivocochlear efferent pathways were intact to that group/treatment ears, OC− = all efferent pathways were lesioned, and COC− = only the crossed efferent pathways lesioned (leaving uncrossed efferent pathways intact).
↵F3-b t tests were performed when the ANOVA indicated significant differences.
↵F3-c Degrees of freedom.
↵F3-d Frequencies for which tvalues were significant at α = 0.05 (i.e., p at least < 0.05).