Mark A. Bee - US grants

0107304
Bee
The International Research Fellow Awards Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.
This award will provide twenty-four months of support to Dr. Mark A. Bee to work with Dr. Georg M. Klump at the University of Oldenburg in Bremen, Germany on the mechanisms of auditory scene analysis in the European Starling.
The purpose of this research is to gain a greater understanding of the underlying neural mechanisms of auditory scene analysis, which is the organization of sounds into perceptual representations of the events that produced the sounds. The PI will study the neural basis of auditory scene analysis in the starling, a songbird that is an excellent model system of behavioral and neurobiological studies of auditory perception. He will use a methodological approach in which microelectrodes are chronically implanted into the starling's auditory cortex and neural responses to acoustic stimuli are recorded from awake, unrestrained birds via radiotelemetry. These experiments will identify areas of the auditory forebrain where different forms of auditory scene analysis occur and how these areas accomplish this complex task. The results will increase our understanding of the mechanisms of auditory scene analysis, contribute to a better understanding of human language acquisition and the evolution of hearing and potentially lead to the development of better hearing aids and voice-recognition-based computer-user interfaces.
Dr. Klump, formerly of the University of Technische Universitat Munchen, is a leading expert in the study of comparative audition and hearing in birds, and is the PI on a grant held by eight research groups in the Munich area focussing on the mechanisms of auditory scene analysis.

[unreadable] DESCRIPTION (provided by applicant): Project Summary: Natural selection for the ability to assign perceived sounds to their correct sources in the environment was a major force driving the early evolution of the vertebrate auditory system. Consequently, we share with non-human vertebrates many of the basic mechanisms responsible for sound source segregation. These mechanisms function in solving the familiar "cocktail party problem" of perceiving speech in the presence of multiple talkers. The users of hearing aids and cochlear implants usually find that their devices provide little or no improvement in speech perception in loud social environments. The long-term goal of the proposed research is to integrate behavioral and electrophysiological experiments in a lower- vertebrate model to achieve a better understanding of the basic signal processing strategies by which vertebrate auditory systems segregate vocal communication signals in noisy social environments. Frogs are a superb model for investigating sound source segregation because reproductive behaviors in this group are mediated by the perception of vocal signals (mating calls) in noisy social aggregations (breeding choruses). That is, frogs must solve their own cocktail-party-like problem to successfully reproduce. This project addresses two specific aims using well-established methods to elicit behavioral responses from female gray treefrogs (Hyla versicolor) to male mating calls: 1. Identify acoustic properties that promote auditory stream segregation of overlapping vocal signals. The working hypothesis for this aim is that differences in fundamental frequency and other acoustic properties of mating calls allow the frog auditory system to segregate the temporally overlapping vocal signals of nearby calling males in a chorus into separate auditory streams. 2. Identify mechanisms for segregating target signals from biologically realistic masking noise. The working hypotheses for this aim are that (i) spatial separation between target signals and "chorus- shaped" noise leads to spatial unmasking and (ii) frogs experience a release from masking by "listening in the dips" of chorus-shaped noise maskers with the modulation statistics of a real chorus. Relevance: A better understanding of how vertebrate auditory systems achieve sound source segregation in noisy social aggregations will lead to advances in the design of hearing prosthetics that improve the ability of the hearing impaired to navigate social interactions in a noisy world. Results from this study, and future related projects that will integrate behavior with electrophysiological methods, are expected to generate new and deeper insights into the mechanisms of sound source segregation in a lower vertebrate model that has evolved to contend with a well-known animal equivalent of the cocktail party problem. [unreadable] [unreadable] [unreadable]

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

In humans and other animals, acoustic communication often takes place in large social groups or "networks" comprising multiple signalers and receivers. In such environments, the background noise generated by simultaneously signaling individuals can impair or "mask" the perception of signals by intended receivers. Auditory masking, in turn, can lead to communication errors. In humans, such errors commonly lead to the misunderstanding of speech in noisy social settings. This project tests the hypothesis that receivers possess psychological mechanisms that function to ameliorate the negative impacts of masking noise by exploiting predictable features of the noise itself. This hypothesis will be tested using frog communication as a model. During their breeding season, male frogs aggregate in choruses and produce loud advertisement calls to attract females. The objectives of the project are to understand how female frogs exploit acoustic features of the noise of a chorus (i) to better recognize the mating calls of their own species, (ii) to discriminate among the calls of their own species and different species, and (iii) to discriminate between preferred and non-preferred males of their own species. The project integrates current paradigms in animal behavior and hearing research and could transform the way research on receiver psychology and communication networks informs the study of human hearing, speech perception, and auditory neuroscience. More broadly, the project will engage the public in the process of scientific inquiry and discovery through the development of a new multi-media exhibit on frogs at a natural history museum and the involvement of citizen scientists in the collection of raw data. The project will also enhance undergraduate and graduate education by developing new project-based learning exercises, a writing-enriched curriculum, and by training graduate students from multiple underrepresented groups in science.

DESCRIPTION (provided by applicant): The broad aim of this research is to better understand the mechanisms of sound source perception. A critical aspect of perceiving distinct sound sources in multi-source environments is the auditory system's ability to separate sounds of interest from other overlapping sounds and background noise. Hearing aids and cochlear implants often provide their users little benefit when it comes to segregating multiple sound sources. Similarly, computer algorithms for automated speech recognition (ASR) also have persistent difficulty segregating multiple sources. A major goal of auditory neuroscience is to uncover the neural mechanisms that perform sound source segregation. A better understanding of these mechanisms, in turn, can lead to biologically-inspired improvements in hearing prosthetics and ASR algorithms. Though seldom stated explicitly in hearing research, the logic of this biomimetic approach is based on evolutionary thinking: the aim is to understand how natural selection has already solved problems of sound source segregation in living organisms. Naturally, most of this work is done using mammalian models because their auditory systems are most similar to those of humans. The project proposed here employs similar logic based on the premise that evolution is well known for finding diverse solutions to common problems in different animal lineages. The long-term goal of the proposed research is to increase knowledge about the mechanisms of sound source segregation by integrating perceptual and neurophysiological experiments in a lower vertebrate model (frogs) with a unique auditory system and an evolutionary history of solving difficult problems of source segregation. This project uses well-established methods to investigate how female tree frogs segregate the mating calls of individual males from the overlapping signals of other males and the general din of noise in a large breeding chorus. The problems that frogs encounter (and solve) when communicating in noisy social aggregations share many similarities with the human cocktail party problem. Three specific aims will investigate the spectral, temporal, and spatial cues that promote sound source segregation. Aim 1 (spatial release from masking) will investigate how the frog auditory system exploits spatial separation between signals and noise to achieve a release from auditory masking. Aim 2 (masking release in modulated noise) will investigate a form of masking release that depends on a listener's ability to exploit temporal fluctuations in background noise levels. Aim 3 (auditory stream segregation) will investigate the perceptual segregation of two overlapping calls. By investigating these aims in frogs, this project is expected to generate insights into the potential diversity of neural mechanism by which evolution has solved problems of source segregation. Hearing prosthetics and computer algorithms for automated speech recognition perform poorly in environments with multiple competing sound sources. A better understanding of how evolution has solved this type of sound source segregation problem in a diversity of animal models could lead to further biologically-inspired technological advances. Results from this study, and future related projects that will integrate behavior with neurophysiological methods, are expected to generate new and deeper insights into the neurosensory mechanisms of sound source segregation in a lower vertebrate model system that evolved to vocally communicate in noisy, multi-source environments.

Humans and other animals often communicate acoustically in noisy social environments. These environments present serious challenges to effective communication when multiple individuals signal simultaneously. A fundamental goal of auditory neuroscience is to understand how nervous systems group together the different sounds produced by one source in the presence of multiple competing sources. This research investigates auditory grouping in an animal model that communicates acoustically in large social groups and has a unique auditory system. The work uses behavioral assays and neural recordings to study how anurans (frogs and toads) use frequency cues to group the discrete sound elements comprising communication signals. Preliminary studies suggested that use of frequency cues by anurans is supported by two mechanisms, one similar to that of mammals and birds and one resulting from the unique physiology of anuran inner ears. Further study will investigate these mechanisms at various levels of the anuran auditory system. It is expected that low levels of the auditory system will use mechanisms similar to those that have been observed in other animals, but that there will be two distinct variations, again reflecting the anuran ears' unique physiology. At higher levels of the auditory system, a new mechanism is expected to manifest which combines frequency cues with temporal cues to produce a neural "readout" of the perceptual state of the animal. This research will contribute to a broader and more general understanding of how auditory systems perceive acoustic communication signals in noisy environments. Such data are essential for understanding the potential diversity of ways that evolution may solve common problems in diverse groups of animals. This basic biological knowledge, in turn, could one day benefit people with impaired hearing. The project also integrates research with the training and teaching of undergraduate and graduate students and additionally will foster an international collaboration.

Human and animal behavior is guided by continuous and often complex sensory input. Nervous systems must parse this input stream and bind together those pieces corresponding to actual objects in the environment. As an illustration, consider the command to STOP. The human visual system effortlessly binds an octagonal shape with red coloration into a unified visual percept that elicits stopping behavior. Likewise, different sounds in the spoken word "stop" become bound into an auditory percept that also elicits stopping behavior. Efforts to understand how nervous systems solve these so-called "binding problems" have advanced the fields of cognitive and computational neuroscience. By comparison, much less is known about how nonhuman animals create bound percepts that correspond to the variety of things of interest to animals (e.g. prey, predators, mates, communication signals). Hence, important knowledge gaps remain concerning the brain mechanisms that allow animals to solve binding problems. This project integrates behavioral and electrophysiological experiments to uncover general mechanisms of auditory perceptual binding in an animal model for which vocal communication in noisy social environments is key to successful reproduction. This research is important because basic knowledge of neurosensory mechanisms that enable animals to solve auditory binding problems could benefit society by helping to improve hearing prosthetics and speech recognition systems, which perform poorly in noisy acoustic scenes. This research will also lead to answering new questions about how neural systems shape the evolution of communication behaviors. In addition, the project will create research experiences for a minimum of 15 undergraduates, advance the training of a postdoctoral scholar, and integrate research and teaching with public outreach aimed at elementary school kids in a large metropolitan area.

The project investigates auditory binding in green treefrogs (Hyla cinerea), a well-known animal model in studies of hearing and sound communication. Aim 1 uses behavioral experiments to identify cues that promote auditory binding. Two experiments will test the hypothesis that synchronous onsets/offsets, common spatial origin, and harmonic relatedness function to bind together separate parts of the frequency spectrum of vocalizations analogous to formants in human vowel sounds. Aim 2 involves electrophysiological recordings from single neurons in the auditory midbrain to identify neural correlates of auditory binding. Three experiments will test the hypothesis that changes in the responses of neurons sensitive to spectral combinations correlate with changes in the behavioral decisions made in response to manipulations of the auditory binding cues from Aim 1.

Humans are not the only animals that recognize familiar individuals. In fact, many animals can recognize their social partners. However, we still know little about the sensory and learning processes by which animals come to recognize familiar individuals and how this behavior evolves. This project uses playback experiments in the wild to compare the processes by which frogs learn to recognize their neighbors. By comparing the behavior of two closely-related frog species that differ in this ability but share a recent evolutionary ancestor, the project will also test how recognition behavior evolved. This project will provide an international experience for undergraduate students, and create materials for both a course at the University of Minnesota and a public museum exhibit at Kaieteur National Park in Guyana.

Male Golden Rocket Frogs recognize and respond less aggressively to the calls of familiar territorial neighbors, while male Kai Rocket Frogs show no evidence of recognition. This project uses habituation-discrimination experiments with natural and synthetic calls to compare the perceptual basis of neighbor recognition in these two species. In the first experiment, the ability of males of both species to discriminate between the calls of different individuals will be examined to test the hypothesis that neighbor recognition evolves by narrowing the specificity of learned social categories. In the second experiment, synthetic calls, in which acoustic properties can be manipulated independently, will be used to test the hypothesis that male golden rocket frogs discriminate between the calls of different individuals using the most reliable acoustic cues of identity.