Syllable classification of USV calls in NEXMIF mice. A, Representative calls of each type used in syllable characterization. B, KO animals showed an increase in Simple type calls and a decrease in Complex type calls compared with WT animals at each time point. C, Call syllable classification at P5 shows an increase in short and flat calls and a decrease in modulated and harmonic calls made by KO animals compared with WT animals. D, KO mice made significantly more short and flat calls compared with WT mice and significantly less modulated and multiple jump calls at P7. E, Call syllable classification at P9 shows an increase in short calls and decrease in modulated, multiple jump, and harmonic calls made by KO animals compared with WT animals. (WT, n = 6; KO, n = 5). Data are represented as average ± SEM. *p < 0.05; **p < 0.01. ns, Not significant.