Figures and data
Click-evoked ABRs appear and gradually mature after hatching in zebra finches.
(A) ABR recording setup. (B) Used sound stimuli. Red, phase inverted signal. (C) Representative, 95 dB SPL click-evoked ABR ante- (black) and post-mortem (red). (D) Representative ABRs to 95 dB SPL clicks at tested DPH timepoints. The first negative peak (I) and the following trough are designated as wave I. Noise RMS is determined from the red area and signal RMS from the blue area. (E) Percentage of animals that exhibited a detectable (S/N > 2) click-evoked ABR. (F) Detection thresholds were measured with a set of clicks with decreasing 5 dB SPL steps. Arrow indicates the determined threshold for this 8 DPH example. (G) Average click thresholds at different DPH ages. Orange box indicates heat whistle playback levels used in previous studies (Katsis et al., 2018). Red box indicates in vivo heat whistle levels at 10 cm distance (Anttonen et al., 2025). (H) Click-evoked ABR wave I amplitude and (I) latency over SPL. Age groups are color-coded in D-I. Shaded areas in H-I = s.e.m.
Sound frequency sensitivity matures over postnatal development.
(A) Representative ABRs to 1 kHz and (B) 8 kHz tone burst stimuli over postnatal development. (C) Zebra finch ABR thresholds obtained with tone bursts (solid lines) and with tone pips (dashed line). Dotted line displays a behavioural threshold reported by Okanoya and Dooling (1987). Shaded areas = s.e.m. The level of heat whistle playbacks used in previous studies (Katsis et al., 2018) (orange box) and the level of in vivo heat whistles at 10 cm distance (Anttonen et al., 2025) (red lines) are just on or below the adult hearing threshold.
Intense sound stimulation induces zebra finch eggs to vibrate at very low velocities.
A Setup used to measure sound induced vibrations of eggs. B Average (N=5) vibration velocity transfer function of a zebra finch egg during a 94 dB SPL sound sweep between 0.25-to-10 kHz. Gray area marks the standard deviation. Green and red areas display the frequency windows related to the best hearing sensitivity of zebra finches and to heat whistles, respectively. C The average egg vibration velocities induced by a 94 dB SPL sounds at frequencies associated with song (green) and with heat whistles (red). Error bars = s.d. D The average egg vibration velocities caused by 67 dB SPL sounds plotted together with thresholds for human (Håkansson et al., 1985) and mouse bone conduction hearing (Chhan et al., 2017) and for human vibrotactile threshold at 0.2 kHz (Mountcastle et al., 1972).
Development of tone burst-evoked auditory brainstem responses.
(A) Percentage of animals displaying tone burst-evoked ABRs at 95 dB SPL. Gray bars indicate animals with S/N < 2. Exact number of animals is displayed above the bars. (B) Changes in tone burst-evoked ABR wave I amplitude and (C) latency over postnatal development. Frequencies are color coded as displayed below the figure. Shaded areas in B,C = s.e.m.
Tone pip-evoked auditory brain stem responses in adult zebra finches.
(A) Representative AC-ABR evoked by a 95 dB SPL, 1 kHz tone pip recorded from an adult zebra finch. (B) Percentage of adult zebra finches showing tone burst-evoked ABRs at 95 dB SPL between 0.25 and 8 kHz. Gray bars indicate responses with S/N < 2.
Statistics for click-evoked auditory brainstem response thresholds.
Statistics for click-evoked auditory brainstem response thresholds.
Statistics for click-evoked auditory brainstem response amplitudes.
Statistics for click-evoked auditory brainstem response latencies.
Statistics for tone burst-evoked auditory brainstem response amplitudes.
