Auditory perception exhibits sexual dimorphism and left telencephalic dominance in Xenopus laevis

Abstract

Sex differences in both vocalization and auditory processing have been commonly found in vocal animals, although the underlying neural mechanisms associated with sexual dimorphism of auditory processing are not well understood. In this study we investigated whether auditory perception exhibits sexual dimorphism in Xenopus laevis To do this we measured event-related potentials (ERPs) evoked by white noise (WN) and conspecific calls in the telencephalon, diencephalon and mesencephalon respectively. Results showed that (1) the N1 amplitudes evoked in the right telencephalon and right diencephalon of males by WN are significantly different from those evoked in females; (2) in males the N1 amplitudes evoked by conspecific calls are significantly different from those evoked by WN; (3) in females the N1 amplitude for the left mesencephalon was significantly lower than for other brain areas, while the P2 and P3 amplitudes for the right mesencephalon were the smallest; in contrast these amplitudes for the left mesencephalon were the smallest in males. These results suggest auditory perception is sexually dimorphic. Moreover, the amplitude of each ERP component (N1, P2 and P3) for the left telencephalon was the largest in females and/or males, suggesting that left telencephalic dominance exists for auditory perception in Xenopus.

Keywords: Auditory perception; Event-related potentials (ERPs); Sexual dimorphism; Telencephalon; Xenopus laevis.

Fig. 1.

Grand average waveforms for different brain regions during playbacks of WN, FS and SF calls, respectively (n=16). Abbreviations: LT and RT, the left and right telencephalon; LD and RD, the left and right diencephalon; LM and RM, the left and right mesencephalon; WN, white noise; FS, fast-slow trill call; SF, slow-fast trill call.

Fig. 2.

Means and standard deviations for the N1 amplitudes evoked by each acoustic stimulus in each brain region for females (A) and males (B), respectively (n=16). Filled stars denote that there were significant differences between different brain areas or different acoustic stimuli (P<0.05). Abbreviations: LT and RT, the left and right telencephalon; LD and RD, the left and right diencephalon; LM and RM, the left and right mesencephalon; WN, white noise; FS, fast-slow trill call; SF, slow-fast trill call.

Fig. 3.

Means and standard deviations for the P2 amplitudes evoked by each acoustic stimulus in each brain region for females (A) and males (B), respectively (n=16). Filled stars and open stars denote that there were significant (P<0.05) and extremely significant (P<0.001) differences between different brain areas, respectively. Abbreviations: LT and RT, the left and right telencephalon; LD and RD, the left and right diencephalon; LM and RM, the left and right mesencephalon; WN, white noise; FS, fast-slow trill call; SF, slow-fast trill call.

Fig. 4.

Means and standard deviations for the P3 amplitudes evoked by each acoustic stimulus in each brain region for females (A) and males (B), respectively (n=16). Filled stars and open stars denote that there were significant (P<0.05) and highly significant (P<0.001) differences between different brain areas, respectively. Abbreviations: LT and RT, the left and right telencephalon; LD and RD, the left and right diencephalon; LM and RM, the left and right mesencephalon; WN, white noise; FS, fast-slow trill call; SF, slow-fast trill call.

Fig. 5.

Electrode placements and 10 s of typical EEG tracings for each channel. The intersection of the three dashed lines in the head of X. laevis denotes the lambda (i.e. the vertex where skull sutures intersect). Abbreviations: LT and RT, the left and right telencephalon; LD and RD, the left and right diencephalon; LM and RM, the left and right mesencephalon. Image adapted from Fan et al. (2018) licensed under https://creativecommons.org/licenses/by/4.0/legalcode CC-BY 4.0 with permission.

Fig. 6.

Waveforms and spectrograms of the three stimuli for a randomly selected stimulus set. (A) WN, white noise; (B) FS, fast-slow trill call; (C) SF, slow-fast trill call. Since the frequency response of the speaker is 0.1–10 kHz, white noise within the same bandwidth is shown.