Figure 1.

Experimental design and attenuation induced by earplugs. A, EPGap and EPSil animals were earplugged from P11 to P24, while CtGap and CtSil animals were sham-treated. On P24, P27, and P30, silence groups were placed in the ASR testing apparatus for 1 h sessions with no auditory stimuli, while gap groups were exposed to 1 h sessions of bandpass noise with intermittent gaps (the same stimulus set used for gap-PPI testing but without the startle stimulus). On P33, P36, and P39, all groups were behaviorally tested for GDTs in 1 h sessions. Each animal underwent cortical recordings on one of the subsequent 8 d. B, ABR thresholds with and without bilateral earplugs, showing earplug-induced attenuation of ∼15–35 dB. Animals were raised with normal hearing experience, and baseline ABRs were measured at P30. Immediately after baseline recordings, earplugs were inserted bilaterally and ABRs were remeasured. Thresholds were quantified as the lowest level to elicit a visible response. *p < 0.04; ***p < 0.001.