Figure 1.
ABR thresholds for click and tone pip stimuli are not altered by maternal experience.
A) Averaged click-evoked auditory brainstem responses (ABRs) (500 presentations per stimulus intensity). All traces are labelled with corresponding absolute stimulus intensity on the y-axis and a black dot denotes the threshold stimulus intensity. ABR peak numbers are labelled with roman numerals. The black horizontal bar on the x-axis denotes the duration of the stimulus. B) ABR thresholds for all stimuli. Dots represent ABR thresholds for individual animals with the middle horizontal bar representing the mean and error bars representing the 95% confidence interval.
Table 1.
Click-evoked ABR peak latencies measured 20 dB above each animal’s threshold.
Table 2.
Click-evoked ABR interpeak latencies measured 20 dB above each animal’s threshold.
Figure 2.
Click-evoked ABR latencies for specific peaks are significantly shorter for mothers than pup-naive females, with cocarers more similar to mothers.
A) Latency to peak I at different absolute sound intensities (latency intensity function, LIF) and B) at 20 dB above ABR threshold. C) LIF for peak II and D) peak II latency at 20 dB above ABR threshold. E) LIF for interpeak latencies between peaks IV and V. No data points are shown for 39 and 44 dB SPL as this peak was not consistently present in all animals at lower stimulus intensities. F) interpeak latencies between peaks IV and V at 20 dB above auditory brainstem response threshold. LIFs in A), C) and E) show means with error bars denoting SEM. Dots in B), D) and F) show individual latencies for each animal with the middle bar representing the mean and error bars denoting 95% confidence intervals. Asterisks indicate statistical significance at p<0.010 in B) and p<0.013 in D) for the indicated post-hoc comparisons, using the Sidak adjusted alpha level.
Figure 3.
Shorter click-evoked ABR latencies in mothers represent a genuine shift towards faster processing.
A) Peak I and B) peak II latencies, and C) IV–V interpeak latencies as a function of age, measured 20 dB above each animal’s threshold. For these peaks, which differed significantly between pup-naive females and mothers, pup-naive females did not show any age-related latency shift. Trend lines refer to pup-naive points only. r2 for all panels is <0.001. Data points for mothers and cocarers are all below these trend lines.
Figure 4.
Maternal experience significantly influences tone pip-evoked ABR peak latencies.
A) Representative averaged traces from individual animals in response to tone pips at different frequencies (500 presentations per stimulus intensity). The black dot to the left of the y-axis denotes the threshold stimulus intensity. Peak I is labelled in each auditory brainstem response with the exception of 80 kHz as we were unable to identify a Peak I latency at this frequency. B) Distributions of latencies for all animals combined. Latencies measured 10 dB above each animal’s threshold. Bin width = 0.02 ms C) Effects of pup-care experience on peak I latencies. Dots show individual latencies for each animal with the middle horizontal bar representing the mean, and error bars denoting 95% confidence intervals. Asterisk indicates significance at the p<0.01 for the indicated post-hoc comparison.
Table 3.
Tone-evoked peak I ABR latencies measured 10 dB above each animal’s threshold.
Figure 5.
Time course and efficacy of hormone manipulation.
A) Timeline of estradiol treatment and auditory brainstem response recordings in relation to the mouse pregnancy and maternal care timeline. B) Change in mass from the beginning of estradiol treatment to the end verifies the expected reduced weight-gain from elevated estradiol levels. Middle bars represent the means; error bars represent 95% confidence intervals.
Figure 6.
Maternal profile of estradiol does not significantly affect ABR peak latencies.
A) Auditory brainstem response (ABR) latencies in response to click stimuli at 20 dB above threshold, at time point ABR3 (∼3 weeks after implant removal). The specific peaks shown are those that differ between mothers and pup-naïve females in the maternal study. B) ABR latencies in response to tone pip stimuli at 10 dB above threshold, at time point ABR3 (∼3 weeks after implant removal). Diamonds represent individual animals with the middle bar representing the mean. Error bars represent 95% confidence intervals.
Table 4.
Estradiol effects on click-evoked ABR latencies measured 20 dB above each animal’s threshold.
Table 5.
Estradiol effects on click-evoked ABR interpeak latencies measured 20 dB above each animal’s threshold.
Table 6.
Estradiol effects on tone-evoked peak I ABR latencies measured 10 dB above each animal’s threshold.