Guangzhan Fang

Acoustic Analysis of the Advertisement Calls of the Music Frog, Babina daunchina

Abstract The acoustic structure of 18 male advertisement calls of the “music frog” (Babina daunchina), indigenous to the Emei mountain area of Sichuan province in southwest China was analyzed. Previous results showed that Babina typically call from within hidden burrows made by the males and must rely strongly on acoustic information for mate choice. Functioning ecologically as nests, burrows are used for mating, egg-laying, and pre- and postembryonic development. Male Babina calls are spectrally and temporally complex consisting of a sequence of 3–8 notes. Each note consists of a stack of frequency bands, which are nearly integer multiples of the fundamental residue. For all calls the fundamental frequency of successive notes increases monotonically. Moreover, there is a negative correlation between the lowest harmonic (F0) value of the first call note and the increments in fundamental frequency between notes in the same call, implying that constraints exist in the production mechanism. Hierarchical cluster and multidimensional scaling analysis of 29 temporal and spectral call parameters indicate that most of the variance between calls and between males is accounted for by three clusters of call features. The first includes 19 tightly correlated temporal and modulation features including note durations and modulation patterns and total call duration. The second cluster includes the successively increasing fundamental frequencies of the call notes and may reflect that individual males can alter fundamental frequency from call to call. The third cluster includes the dominant frequency bands in calls and may reflect the filter properties of each males burrow.

Electroencephalogram bands modulated by vigilance states in an anuran species: a factor analytic approach

Dramatic changes in neocortical electroencephalogram (EEG) rhythms are associated with the sleep–waking cycle in mammals. Although amphibians are thought to lack a neocortical homologue, changes in rest–activity states occur in these species. In the present study, EEG signals were recorded from the surface of the cerebral hemispheres and midbrain on both sides of the brain in an anuran species, Babina daunchina, using electrodes contacting the meninges in order to measure changes in mean EEG power across behavioral states. Functionally relevant frequency bands were identified using factor analysis. The results indicate that: (1) EEG power was concentrated in four frequency bands during the awake or active state and in three frequency bands during rest; (2) EEG bands in frogs differed substantially from humans, especially in the fast frequency band; (3) bursts similar to mammalian sleep spindles, which occur in non-rapid eye movement mammalian sleep, were observed when frogs were at rest suggesting sleep spindle-like EEG activity appeared prior to the evolution of mammals.

Circadian Rhythm of Calling Behavior in the Emei Music Frog (Babina daunchina) is Associated with Habitat Temperature and Relative Humidity

Generally, the function of vocalizations made by male anurans are to attract females or defend resources. Typically, males vocalize in choruses during one or more periods in a twenty-four-hour cycle, which varies, however, among species. Nevertheless, the causal factors influencing circadian variations of calling patterns in anuran species are not clear. In this study, male chorus vocalizations were monitored in the Emei music frog (Babina daunchina) for 17 consecutive days during the breeding season, while its habitat air temperature and relative humidity in the course of experiments were measured as well. The results revealed that the circadian calling patterns were characterized by two periods of peak vocalization, which were observed from 0500 h to 0700 h and from 1300 h to 2000 h, while the lowest activity period was found from 2100 h to 2200 h. Both calls/h and notes/h were positively correlated with air temperature and negatively with relative humidity. Overall, our data indicate that the Emei music frogs (B. daunchina) could regulate their vocal activities based on the changes of physical micro-environment (e. g., temperature or humidity) to maximize reproductive success.

The biological significance of acoustic stimuli determines ear preference in the music frog

ABSTRACT Behavioral and neurophysiological studies support the idea that right ear advantage (REA) exists for perception of conspecific vocal signals in birds and mammals. Nevertheless, few studies have focused on anuran species that typically communicate through vocalization. The present study examined the direction and latencies of orientation behaviors in Emei music frogs (Babina daunchina) produced in response to six auditory stimuli emitted by a speaker placed directly behind the subjects. The stimuli included male advertisement calls produced from within burrow nests, which have been shown to be highly sexually attractive (HSA), calls produced from outside burrows, which are of low sexual attractiveness (LSA), screech calls produced when frogs are attacked by snakes, white noise, thunder and silence. For all sound stimuli except the screech, the frogs preferentially turned to the right. Right ear preference was strongest for HSA calls. For the screech and thunder stimuli, there was an increased tendency for subjects to move further from the speaker rather than turning. These results support the idea that in anurans, right ear preference is associated with perception of positive or neutral signals such as the conspecific advertisement call and white noise, while a left ear preference is associated with perception of negative signals such as predatory attack. Highlighted Article: Right ear advantage is demonstrated behaviorally in an anuran through an orientation task, which shows that differences in bio-significance induce variable responses, suggesting orientations are affected by mating strategy and emotion processing.

Mating signals indicating sexual receptiveness induce unique spatio-temporal EEG theta patterns in an anuran species.

Female mate choice is of importance for individual fitness as well as a determining factor in genetic diversity and speciation. Nevertheless relatively little is known about how females process information acquired from males during mate selection. In the Emei music frog, Babina daunchina, males normally call from hidden burrows and females in the reproductive stage prefer male calls produced from inside burrows compared with ones from outside burrows. The present study evaluated changes in electroencephalogram (EEG) power output in four frequency bands induced by male courtship vocalizations on both sides of the telencephalon and mesencephalon in females. The results show that (1) both the values of left hemispheric theta relative power and global lateralization in the theta band are modulated by the sexual attractiveness of the acoustic stimulus in the reproductive stage, suggesting the theta oscillation is closely correlated with processing information associated with mate choice; (2) mean relative power in the beta band is significantly greater in the mesencephalon than the left telencephalon, regardless of reproductive status or the biological significance of signals, indicating it is associated with processing acoustic features and (3) relative power in the delta and alpha bands are not affected by reproductive status or acoustic stimuli. The results imply that EEG power in the theta and beta bands reflect different information processing mechanisms related to vocal recognition and auditory perception in anurans.

Right ear advantage for vocal communication in frogs results from both structural asymmetry and attention modulation

Right-ear/left-hemisphere advantage (REA) in processing species-specific vocalizations has been demonstrated in mammals including humans. Two models for REA are typically proposed, a structural model and an attentional model. These hypotheses were tested in an anuran species, the Emei music frog (Babina daunchina) in which females strongly prefer male calls produced from inside mud-retuse burrows (high sexual attractiveness or HSA calls) to those produced in open fields (low sexual attractiveness or LSA calls). Isochronic playbacks were used to control for attention to stimuli presented to either the left or right sides of female subjects while electroencephalogram (EEG) signals were recorded from the left and right midbrain and telencephalon. The results show that relative EEG power in the delta band declined while those of the alpha and beta bands increased with time in the left but not the right midbrain. Since the anuran midbrain receives auditory information derived primarily from the contralateral auditory nerve, these results support the idea that REA occurs in frogs because communication sounds are processed preferentially in the left midbrain. Furthermore, though differences in the dynamic changes of the delta, alpha and beta bands in the left midbrain between acoustic stimuli were not statistically significant, these changes were stronger during the playback of HSA calls toward which females tend to allocate greater attentional resources. These results imply that REA in frogs results from the combined effects of structural asymmetry and attention modulation.

Electroencephalographic signals synchronize with behaviors and are sexually dimorphic during the light-dark cycle in reproductive frogs

Male frogs behave differently from females during the breeding season, particularly with respect to courtship displays and in response to mating signals. In search of physiological correlates of these differences, the present study measured changes in baseline electroencephalogram (EEG) power output within four frequency bands in the telencephalon and mesencephalon, together with changes in locomotor activity as a function of the light–dark cycle in male and female Emei music frogs (Babina daunchina) at the reproductive stage. Previous studies have shown that male vocal activity varies both seasonally and daily in this species and that females use male advertisement calls to locate and select mates. The present results show that both EEG and locomotor activity exhibit highly correlated circadian patterns with peaks around light onset and offset. Importantly, during the reproductive stage, statistically significant sex differences in EEG output across brain regions during the light and dark phases were found indicating that sexual dimorphism exists for EEG activity which may underlie sexually specific information processing and behavioral activities.

Long-range correlations of different EEG derivations in rats: sleep stage-dependent generators may play a key role

For the electroencephalogram (EEG), topographic differences in the long-range temporal correlations would imply that these signals might be affected by specific mechanisms related to the generation of a given neuronal process. So the properties of the generators of various EEG oscillations might be investigated by their spatial differences of the long-range temporal correlations. In the present study, these correlations were characterized with respect to their topography during different vigilance states by detrended fluctuation analysis (DFA). The results indicated that (1) most of the scaling exponents acquired from different EEG derivations for various oscillations were significantly different in each vigilance state; these differences might be resulted from the different quantities and different locations of sleep stage-dependent generators of various neuronal processes; (2) there might be multiple generators of delta and theta over the brain and many of them were sleep stage-dependent; (3) the best site of the frontal electrode in a fronto-parietal bipolar electrode for sleep staging might be above the anterior midline cortex. We suggest that DFA analysis can be used to explore the properties of the generators of a given neuronal oscillation, and the localizations of these generators if more electrodes are involved.

Sound Classification and Call Discrimination Are Decoded in Order as Revealed by Event-Related Potential Components in Frogs

Species that use communication sounds to coordinate social and reproductive behavior must be able to distinguish vocalizations from nonvocal sounds as well as to identify individual vocalization types. In this study we sought to identify the neural localization of the processes involved and the temporal order in which they occur in an anuran species, the music frog Babina daunchina. To do this we measured telencephalic and mesencephalic event-related potentials (ERPs) elicited by synthesized white noise (WN), highly sexually attractive (HSA) calls produced by males from inside nests and male calls of low sexual attractiveness (LSA) produced outside of nests. Each stimulus possessed similar temporal structures. The results showed the following: (1) the amplitudes of the first negative ERP component (N1) at ∼100 ms differed significantly between WN and conspecific calls but not between HSA and LSA calls, indicating that discrimination between conspecific calls and nonvocal sounds occurs in ∼100 ms, (2) the amplitudes of the second positive ERP component (P2) at ∼200 ms in the difference waves between HSA calls and WN were significantly higher than between LSA calls and WN in the right telencephalon, implying that call characteristic identification occurs in ∼200 ms and (3) WN evoked a larger third positive ERP component (P3) at ∼300 ms than conspecific calls, suggesting the frogs had classified the conspecific calls into one category and perceived WN as novel. Thus, both the detection of sounds and the identification of call characteristics are accomplished quickly in a specific temporal order, as reflected by ERP components. In addition, the most dynamic ERP patterns appeared in the left mesencephalon and the right telencephalon, indicating the two brain regions might play key roles in anuran vocal communication.

Changes in electroencephalographic power spectra associated with reproductive status in frog

Electroencephalogram (EEG) waveforms reflect the summed slow potentials generated by cortical neurons and can therefore be used to infer functional processes. In many species, individuals in the reproductive stage are more active and sensitive to species-typical stimuli than those in the nonreproductive stage. In the present study, changes in EEG power spectra were examined with respect to reproductive status in the music frog, Babina daunchina. The results indicated that in the reproductive stage, (1) power spectra of all EEG oscillations except for theta were significantly higher than in the non-reproductive stage; (2) for delta, significant increase of the power spectrum only appeared in the right hemisphere; and (3) the brain exhibited leftdominance of EEG spectra in the telencephalon and right-dominance of EEG spectra in the mesencephalon, providing evidence of lateralization of function. It is likely that sex hormone differences in the reproductive stage mediate these phenomena, through expression of their receptors, transcriptional regulatory elements, in specific regions of the forebrain and midbrain.