Table 1.
Test groups and experimental conditions of laterality of loud tone exposure (loud tone always at 13 kHz, 100 dB SPL for 10 min) and background to exposure
| Group | Status of efferent pathways [All pathways intact/All pathways cut/Only crossed pathways cut (leaving intact uncrossed pathways)] | Loud tone exposure laterality | Background to the tone exposure |
|---|---|---|---|
| Groups to establish the basic protective effects of cochlear efferents | |||
| Silence 1 | All pathways intact | Monaural | Silence |
| Silence 2 | All pathways intact | Binaural | Silence |
| Silence 3 | Ear 1: all pathways intact | Binaural | Silence |
| Ear 2: all pathways cut | |||
| Silence 4 | Ear 1: only crossed pathways cut | Binaural | Silence |
| Ear 2: only crossed pathways cut | |||
| Groups to establish that cochlear efferents provide extra protection in noise backgrounds | |||
| Noise 1 | Ear 1: all pathways intact | Binaural | Binaural Noise @ 40 dB SPL |
| Ear 2: all pathways cut | |||
| Noise 2 | Ear 1: all pathways intact | Binaural | Binaural Noise @ 60 dB SPL |
| Ear 2: all pathways cut | |||
| Noise 3 | Ear 1: all pathways intact | Binaural | Binaural Noise @ 80 dB SPL |
| Ear 2: all pathways cut | |||
| Groups to establish the role of uncrossed pathways in extra protection by cochlear efferents in noise background | |||
| Noise 4 | Ear 1: only crossed pathways cut | Binaural | Binaural Noise @ 80 dB SPL |
| Ear 2: only crossed pathways cut | |||
| Noise 5 | Ear 1: only crossed pathways cut | Binaural | Binaural Noise @ 80 dB SPL |
| Ear 2: all pathways cut | |||
| Noise 6 | All pathways intact | Monaural | Monaural Noise @ 80 dB SPL |
| Noise 7 | Ear 1: only crossed pathways cut | Monaural | Monaural Noise @ 80 dB SPL |
| Ear 2: all pathways cut | Monaural | Monaural Noise @ 80 dB SPL | |
