Bats are social organisms that live in large colonies. However, reliance upon echolocation in order to hunt and navigate, means that bats also face pressing acoustic challenges due to overlap with surrounding noise. Bats also possess fine control over the properties of their echolocation pulses. This study's goal was to determine how bats are able to effectively function in large groups despite the interfering noise generated by conspecifics. Mexican free-tailed bats (Tadarida brasiliensis) were exposed to both artificially generated interfering noises and noise generated by conspecifics, and the temporal characteristics of their resulting echolocation calls were analyzed. In addition, bats were given injections of dopaminergic and serotonergic drugs, in an effort to determine which monoamine(s) were capable of altering vocal motor timing and to determine which regions of the brain play a role in regulating the timing of echolocation. I hypothesized that bats would alter the timing of emission of their own echolocation pulses in response to noise, and that drugs affecting the 5HT2A receptor would shift the timing of emission of echolocation pulses. The first part of this dissertation describes a novel temporal alteration behavior that occurs in response to artificially generated intermittent noise, and is characterized by a period of pulse suppression followed by a gradual return to normal call rates. Bats alter the timing of emission of their echolocation pulses to avoid overlap with noise and call within silent periods. The second part of this study investigated whether dopamine or serotonin, or both, could alter the timing of this vocal behavior. The results of this study were inconclusive, although I found some evidence that 5HT2A agonists can produce faster responses. Finally, I show that echolocating bats suppress pulse emission in nearby conspecifics. The resulting decrease in call rate leads to an overall increase in information throughput. This study also demonstrates that bats respond to continuous noise by increasing their call rate, and that the switch between the responses to intermittent noise and continuous noise occurs at a duty cycle of 50% or higher. Overall, this dissertation establishes that bats alter the timing of emission of their echolocation calls in response to noise, and that these mechanisms may be regulated by serotoninergic mechanisms.

No description available.

付記する学位プログラム名: 霊長類学・ワイルドライフサイエンス・リーディング大学院 / 京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20045号 / 理博第4230号 / 新制||理||1609(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 Michael Alan Huffman, 准教授 後藤 幸織, 教授 平井 啓久 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Female mallard ducks (Anas platyrhynchos) exhibit diverse vocalizations. Duck hunters mimic these vocalizations using artificial calls made from hardwoods or plastics. Hardness of these calls and extent to which humans can mimic live mallards using an artificial call were unknown before this study. I compared hardness of 7 species of hardwoods and cast acrylic and found acrylic, cocobolo (Dalbergia retusa), bocote (Cordia alliodora), osage orange (Maclura pomifera), and pecan (Carya sp.) were the hardest materials tested. I also compared acoustic metrics of field recordings of vocalizing female mallards to those of experienced duck callers using calls of these materials equipped with single or double reeds. I found that cocobolo, osage orange, pecan, acrylic, and bocote calls with double reeds were acoustically most similar to female mallards. I recommend that duck call manufacturers use acrylics and harder wood species with single or double reeds, recognizing that double reed calls generally performed superior in this study.

Master of Science / Department of Psychological Sciences / Mary Cain / Novelty-seeking and sensation-seeking are traits implicated in initial drug experimentation and relapse in human populations. To research the neurobiological substrates that are implicated in novelty/sensation-seeking that predispose an individual to drug use, a rodent model was used. Recently, 50 kHz ultrasonic vocalizations (USV) have been identified as indices of affective state and are evoked by several drugs of abuse, specifically when these drugs of abuse have their pharmacological effects in the mesolimbic dopamine path. Secondly, genetic breeding of high and low vocalizers suggests not only are they different in the calling frequency, but also to drug sensitivity, suggesting ultrasonic vocalizations may be a behavioral marker for individual differences in the mesolimbic dopamine circuit. Two sensation/novelty seeking screens and an ultrasonic vocalization screen were used in rats to predict the locomotor and 50 kHz USV response to a low (.3 mg/kg) and high dose (1.0 mg/kg) of amphetamine. Correlation analysis revealed none of the novelty screens were correlated. Simultaneous regression analyses indicated amphetamine dose-dependently increased locomotor activity acutely and chronically but did not increase 50 kHz USV. The USV assessment predicted USV response to amphetamine acutely and chronically but was not dose dependent. No interactions among any predictors were observed. Previous research has dichotomized the novelty/sensation-seeking trait and found significant differences between high and low novelty responders. The current research provides evidence for maintaining continuous individual difference variables, and suggests each screen measures a different trait implicated in addiction.

Much of the research examining emotion induction, regulation, and suppression considers solely the visual modality (e.g., pictures of faces) for emotion elicitation. In reality, emotions are cued, expressed, and interpreted through multiple modalities by employing the extensive use of auditory stimuli in addition to visual stimuli. There have been some recent efforts to offset this imbalance in modality preference by using emotional auditory stimuli alone or in addition to visual stimuli. This project aims to further investigate emotional and autonomic responding to auditory stimuli with the added component of examining differential responding across social (nonlinguistic vocal expression) and non-social auditory (music) emotional stimuli. We found mixed support indicating that our auditory stimuli induced physiological changes compared to a neutral condition. We also found that participants reported experiencing emotions congruent with those expressed by the stimuli. Most interestingly, increased autonomic activation was found in vocalizations compared to music possibly indicating more salient emotional responding to voices expressing nonverbal emotions compared to other types of less social emotional stimuli such as music. We discuss these findings through a lens that is not only interested in these potential differences as being driven by vocalizations, but also the unique nature of musical stimuli. This project presents a novel way to further our scientific understanding of the salience of auditory emotional information and the possible differences and similarities in processing more instinctive vocalizations and instrumental music.

Phocid seals (true seals, Order Carnivora, Family Phocidae) use a diverse array of breeding habitats and strategies, and produce many vocalizations. Therefore, phocids are well suited as subjects for study of reproductive strategies and the role of vocalizations in species mating at sea. However, the amount of information is still limited for aquatically breeding pinnipeds. Using underwater audio and video recordings of Weddell seals (Leptonychotes weddellii) interacting in McMurdo Sound, I compared the frequencies of vocalizations and behaviors of males and females during the mating season. I also investigated differences in these frequencies based on the social context. Finally, I identified patterns of vocalizations and behaviors to help determine the behavioral context of calls and used this information as a basis for considering the degree of ritualization in Weddell seal displays. Mews, growls, knocks, and trills were found to be almost exclusively male-specific. The territorial male produced chirps more often when another male was present in its territory; whereas, mews and growls were more frequent when one or more free-ranging females were present. Several vocal and behavioral padeparture of the territorial male into or from the breathing hole. In the context of an evolutionary-based model of communication, these findings suggest that low-frequency vocalizations and stereotyped displays produced by territorial males may have been favored by sexual selection: they may provide reliable information to females about the fitness of the signaler and influence their choice of mate. They may also help in limiting conflicts between the territorial male and females over access to the breathing hole.

A series of five experiments was conducted to determine whether operant or respondent factors controlled the emission of a particular vocalization ( "Q" ) by human infants 16 to 18 months old. Experiment 1 consisted of a pilot investigation of the effects of an autoshaping procedure on three infants' vocal behavior. All three subjects demonstrated increased emission of the target sound during the CR period. Experiments 2 through 4 attempted to replicate the findings of Experiment 1 under controlled conditions, and failed to do so. Experiment 5a presented infant subjects with a discrete-trial operant procedure (having the identical temporal parameters as the autoshaping procedure used in Experiments 1 through 4) , during which subjects received rewards only after emitting the target sound. All three experimentally naive subjects in this condition emitted the target sounds, and each met an acquisition criterion of 15 successive trials with at least one target response (CR) per trial. Subjects in Experiment 5b were exposed to the autoshaping procedure employed in Experiments 1 through 4; in addition, they were rewarded verbally for emitting the target sound at any time during the session. One of these three subjects increased her rate of target sound emission, but never met the acquisition criterion. The results suggest that vocalizations of subjects in this age range are susceptible to response-reinforcer (operant) manipulations and not to stimulus-stimulus (Pavlovian) associations. This conclusion differs from the findings of previous investigations that used younger infant subjects, suggesting that subject age may be important when conditioning vocalizations. Further research is also recommended to determine the utility of employing autoshaping procedures with humans.

No description available.

<p>This dissertation focuses on two vital challenges in relation to whale acoustic signals: detection and classification.</p><p>In detection, we evaluated the influence of the uncertain ocean environment on the spectrogram-based detector, and derived the likelihood ratio of the proposed Short Time Fourier Transform detector. Experimental results showed that the proposed detector outperforms detectors based on the spectrogram. The proposed detector is more sensitive to environmental changes because it includes phase information.</p><p>In classification, our focus is on finding a robust and sparse representation of whale vocalizations. Because whale vocalizations can be modeled as polynomial phase signals, we can represent the whale calls by their polynomial phase coefficients. In this dissertation, we used the Weyl transform to capture chirp rate information, and used a two dimensional feature set to represent whale vocalizations globally. Experimental results showed that our Weyl feature set outperforms chirplet coefficients and MFCC (Mel Frequency Cepstral Coefficients) when applied to our collected data.</p><p>Since whale vocalizations can be represented by polynomial phase coefficients, it is plausible that the signals lie on a manifold parameterized by these coefficients. We also studied the intrinsic structure of high dimensional whale data by exploiting its geometry. Experimental results showed that nonlinear mappings such as Laplacian Eigenmap and ISOMAP outperform linear mappings such as PCA and MDS, suggesting that the whale acoustic data is nonlinear.</p><p>We also explored deep learning algorithms on whale acoustic data. We built each layer as convolutions with either a PCA filter bank (PCANet) or a DCT filter bank (DCTNet). With the DCT filter bank, each layer has different a time-frequency scale representation, and from this, one can extract different physical information. Experimental results showed that our PCANet and DCTNet achieve high classification rate on the whale vocalization data set. The word error rate of the DCTNet feature is similar to the MFSC in speech recognition tasks, suggesting that the convolutional network is able to reveal acoustic content of speech signals.</p> / Dissertation