Eclipse ep25

The Auditory Brainstem Responses (ABRs) of the rats were recorded under anesthesia with 45 mg/kg ketamine hydrochloride (Ketalar^®, Zentiva, İstanbul, Turkey) and 5 mg/kg xylazine hydrochloride applied intraperitoneally to both groups. The ABR recordings were obtained with 50 dB nHL click stimuli, which were applied using insert earphones and subcutaneous needle electrodes. During the tests, the active electrode was placed at the vertex, reference electrode was placed at the ipsilateral mastoid, and ground electrode was placed on the back of the rats. We recorded 500 sweeps for each test and employed a 0.3–3.0 kHz filter. All recording was performed using an Eclipse EP25 (Interacoustics, Denmark). The latency of wave V and interpeak wave latency of waves I–V were analyzed for both ears.

ABR was used to evaluate the involvement of the auditory pathway and was obtained while the subject was sitting comfortably in a soundproof room. Recording was performed with an Interacoustics Eclipse EP25 (Interacoustics AS, Drejervaenget 8, DK-5610 Assens, Denmark) with a 21-stimuli-per-second click rate, in an analysis window of 12 ms. Further details regarding ABR are explained in the Supplementary Materials. Assessment of PTA at octave frequencies between 125 and 8000 Hz was performed using frequency-modulated tones in a standard soundproofed booth. Assessment was performed through an auricle audiometer (Otometrics, Taastrup, Denmark) connected to TDH39 headphones (see Supplementary Materials). Speech perception in quiet was assessed with balanced sentence lists from the Italian Speech Audiometry [57 (link)], with the speech signal at 65 dB SPL presented at 0° to the participant’s head. The score ranges from 0 to 100%. Speech perception in noise was evaluated using the Matrix tests [58 (link)] adapted in Italian (see Supplementary Materials).

ABR tests were conducted using the Eclipse EP25 platform (Interacoustics, Denmark) with insert earphones (3A, Etymotic Research, US). Alternating short-duration clicks with a repetition rate of 19.3 Hz were used as stimuli. Parameters for the test are detailed.

Previously, we showed that the suprathreshold amplitude of ABR responses is associated with the thickness of temporal and parietal cortices (Delano et al., 2020 (link)). For this reason, in this study, we included the measurement of suprathreshold ABR waves I and V. We used an Eclipse EP25 with research licensed equipment (Interacoustics™^®, Middelfart, Denmark) to elicit ABR. The stimuli were broadband clicks delivered through E-A-RTONE™ 3A inserts earphones, with an intensity of 80 dB nHL, and a duration of 100 μs. We used high pass 100 Hz filters and low pass 3,000 Hz filters. Responses were recorded using active electrodes placed on both mastoids and on the forehead (reference or non-inverting), and a ground electrode was secured over the right brow. Waves I to V were identified from two averages of 2,000 repetitions. The amplitudes of waves I and V were defined from the peaks of the respective waves and the negative troughs that followed, and latency from peaks. Amplitude and latency of wave V were measurable in all subjects, while wave I was identified in 109/116 (93.9%) of the cases. When waves I were missing (with detectable wave V), they were imputed with the lower observed value for the amplitude of wave I and the greater observed value for the latency of wave I (Delano et al., 2020 (link)).