Dennis L. Barbour - US grants

[unreadable] DESCRIPTION (provided by applicant): This project addresses our long-term goal to improve our understanding of the mechanisms underlying environmental and communication sound encoding in the mammalian auditory system. Extracting behaviorally relevant information from noisy acoustic signals remains a considerable challenge for engineers of artificial acoustic processing systems, while biological auditory systems seem exquisitely well-suited to such tasks. Understanding the normal encoding of sounds in biological systems will enable us to design more functional artificial sound processors such as hearing aids or hearing-assist devices, as well as to appropriately design auditory neural prostheses intended to interface with malfunctioning human auditory areas. We study common marmosets (Callithrix jacchus) because they are one of the most vocal primate species and because their auditory cortical structure bears considerable similarity to that of humans. Marmoset auditory cortical neurons have been shown to exhibit complex, often nonlinear, responses to wideband sounds such as vocalizations. Most such neurons respond to narrowband sounds only over a relatively narrow range of frequencies. We seek to establish through a series of experiments that neuronal inputs wide- ranging in frequency are responsible for at least some of the previously observed complex responses. The project's research goals will be pursued through the following specific aims: 1) Test the hypothesis that spectral contrast tuning is mediated, in part, by frequencies outside a neuron's classically defined receptive field. Such a finding would provide stronger evidence that these neurons, previously described by the investigator, operate preferentially in conditions of wideband background noise. 2) Test the hypothesis that natural, wideband sounds elicit spikes with more information content than when these sounds are filtered to match the neurons' classical receptive field, particularly for contrast-tuned neurons. Visual cortex neurons exhibit this property, which reveals that the neurons have response properties well-matched to natural visual scenes. If confirmed, these hypotheses would imply that biological auditory systems may be integrating sound energy over a wider frequency range than has been previously estimated. Consequently, artificial systems designed for individuals with hearing loss may be able to exploit these biologically-inspired, wideband coding schemes to ultimately improve these individuals' ability to communicate in real-world situations. This project addresses our long-term goal to improve our understanding of the mechanisms underlying environmental and communication sound encoding in the mammalian auditory system by evaluating how neurons in primate auditory cortex integrate sound energy over a wide range of frequencies. Understanding biological frequency integration may aid engineers in improving auditory prosthesis devices to improving sound encoding in natural everyday environments such as in a noisy room. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): The normal auditory system possesses exquisitely well-adapted processes for extracting behaviorally relevant acoustic signals from the environment, especially under challenging listening conditions such as in the presence of competing signals or background noise. These processes are poorly understood physiologically, however. The objective of this proposal is to understand the neurobiology of a particular auditory processing nonlinearity (auditory spectral contrast tuning) as it relates to noisy vocalization representation in the mammalian auditory system. Aim 1 will involve measuring the sound frequency range that auditory neurons use for making estimates of spectral contrast. This information will prove critical for understanding how contrast tuning is computed biologically. Aim 2 will determine the coding portion of the input/output function for neurons tuned to spectral contrast. The nature of this function will allow inferences to be made about how this particular processing feature is read out by neurons at a later processing stage. Aim 3 will directly test the responses of contrast-tuned neurons to vocalizations embedded in background noise, with the expectation that noisy vocalizations will produce spiking responses in these neurons that carry more information as the amount of noise increases, up to a limit. When completed, this research will result in an improved understanding of a potentially important response property in the central auditory system with potential relevance for engineered noise-reduction systems, which could have great potential for individuals reliant upon a hearing prosthesis for acts of daily living. This project addresses our long-term goal of understanding more clearly how environmental and communication sounds are encoded in the mammalian auditory system under noisy conditions. We will achieve this goal by exploring how particular nonlinear processing features of neurons in primate auditory cortex are created, encode stimulus features and respond to vocalizations degraded by noise. Ultimately, this information may aid in refining algorithms that could allow auditory prosthesis devices such as hearing aids and cochlear implants to function better in everyday noisy environments.

DESCRIPTION (provided by applicant): Project Summary The fields of biology, psychology, and biomedical engineering have generated exciting new advances in the study of neural systems underlying behavior. Individually, these disciplines have individually provided novel insights into brain function and provide opportunities for improved understanding of disorders of the nervous system, healthy and disordered development, and communication. However, the rapid advancement of scientific progress has been limited by the boundaries surrounding the disciplines. Moreover, neuroscientists that are firmly grounded in an array of approaches used by biologists, psychologists, and engineers will best advance new research technologies such as non-invasive functional imaging and neural prosthetics. A training model that is thoroughly interdisciplinary is needed. At Washington University, we have developed such a model: The Cognitive, Computational, and Systems Neuroscience (CCSN) Pathway produces rigorously trained independent investigators that will lead a new generation of scientists who study the brain in truly integrated interdisciplinary investigations. CCSN serves students from the PhD programs in Biomedical Engineering, Psychology, and Neuroscience. The core of CCSN is a two-year curriculum that emphasizes interdisciplinarity, collaboration, and project-based instruction. In the first year, students take courses that bring them up to speed on the core concepts and methods in Cognitive Psychology, Biological Neural Computation, and Neural Systems. In the second year, students participate in two unique courses that have been specially designed as the capstone to the CCSN pathway Advanced CCSN and Project Building in CCSN. Advanced CCSN consists of a series of interdisciplinary case studies in cutting-edge brain science topics. Each topic is presented as a module by a faculty team drawn from the three home programs. Modules include team-based projects and peer review as well as primary source readings and classroom lectures and discussions. Project Building in CCSN is a fully student-driven course. In collaboration with the faculty leader, each student designs an independent interdisciplinary research project. The faculty leader helps them to assemble an interdisciplinary faculty advising team, to whom they present their project multiple times throughout the semester. Faculty advising is complemented by peer advising including written peer review, culminating in a research grant-style project proposal. Surrounding the core CCSN curriculum is a rich penumbra of activities. These are designed to provide intellectual training and to build a cohort of scientists with the identification and social skills necessary to conduct research in interdisciplinary teams. Formal coursework is provided in Mathematics and Statistics of Experimental Neuroscience, and by an intensive mini- course preceding Advanced CCSN. Immersive Encounters with distinguished visiting scientists provide high-intensity exposure to cutting-edge research. In collaboration with the Saint Louis Science Center, CCSN trains students to communicate with the public and helps them build programs and presentations to teach children and adults about the brain and mind. In its initial phases, CCSN has produced cohorts of young brain scientists on the fast track to new discoveries. Evaluations from students, faculty, and an outside advisory team indicate the pathway is on track for continued growth.