Catherine Carr
Nervous systems can resolve microsecond time differences. These time differences would seem too small for single neurons to resolve, because neural events occur on a millisecond, rather than a microsecond, time scale. Accurate coding of temporal information is widespread, however, and many theories of sensory biology depend upon the detection of signals that are correlated in time. Mechanisms of time coding have proven to be particularly accessible in the bird's auditory brainstem. Present studies in the Carr laboratory address how time coding arises during the development of the avian auditory system, how timing information is preserved and improved in the CNS, and how temporal coding circuits evolve. The analysis of temporally ordered inputs is integral to processing both sound localization and communication signals such as speech. Many of these studies are collaborative and take advantage of the resources of the NIH and other area research facilities.

Avis Cohen
Dr. Cohen's group focuses on how systems work. The model used is the lamprey and its locomotion. The group combines physiology, anatomy, behavior and modeling to understand how the levels of organization of the animal/environment interact to produce an adaptive motor pattern. They also look at animals with spinal injuries to determine the impact of regeneration on the animals' ability to swim adaptively. They have two global aims in their lab, understanding how systems work, and understanding the potential problems associated with spinal cord regeneration and finding solutions. They have evidence that regeneration in lamprey, while clearly a reality, can easily lead to problems for the animal. They are investigating the origin of these problems. In association with these goals, they develop mathematical treatments of oscillatory and locomotor systems. Some are more abstract mathematical models, some are neural network models, and others are powerful statistical tools for analysis of rhythmic patterns. Recently they have begun to investigate the use of Very Large Scale Integration (VLSI) integrated circuit techniques as a modeling tool. Avis Cohen, aside from her lab research, is one of directors of the annual Workshop on Neuromorphic Engineering at Telluride, Colorado.

Robert Dooling
Dr. Dooling's research examines the perception of complex sounds by birds to understand such phenomena as vocal learning in birds, the return of auditory function following hair cell regeneration, whether speech is special, and the evolution of mechanisms of hearing. The comparative approach seeks to identify both specializations (i.e. unique to a species) as well as the general biological principles which are capable of organizing and maintaining a complex, learned vocal communication system. Species comparisons allow complex behavior to be meaningfully characterized along the dimensions of learned versus innate, open versus closed genetic programs for development, or special versus general perceptual, cognitive, and motor processes maintaining complex behavior in adulthood. Current work is showing, among other things, that birds are specialized for the temporal resolution of complex acoustic signals. Current work is also aimed understanding the genetic hearing abnormality in a strain of canary (the Belgian Waterslager canary) and the effect that peripheral abnormalities (i.e. missing hair cells) has on function and on CNS anatomy and function in different avian species.

William Hall
Professor Hall's research is focused on the use of animal models of communication to understand the neural basis of human language learning. His current work is on the emergence of functional auditory pathways. The overall goal is to elucidate neuroanatomical changes occurring in the forebrain of nestling budgerigars (m. undulatus) which underlies the emergence of auditory-vocal learning ability during early post-hatch development. It is of interest when connections occur between auditory and vocal nuclei, and when connections between vocal control nuclei, which receive auditory input, form with those which project to brainstem nuclei controlling respiratory and syringeal motorneurons. There is now overwhelming evidence that long term changes in neuronal function, such as those which underlie learning and memory, depend on the expression of immediate early gene proteins. We use pathway tracing in conjunction with IEG immunohistochemistry in order to identify the projections of neurons which exhibit expression of specific IEGs at each stage of vocal development.

William Hodos
One of the most enduring mysteries of the avian visual system is the failure to find deficits in various aspects of spatial vision, such as coarse patterns or even visual acuity, after lesions of the thalamofugal visual pathway. We propose to use more sophisticated methods of visual analysis (the contrast sensitivity function) and selective lesions in the visual thalamus to determine the extent to which the thalamofugal pathway is involved in visual performance. A second set of visual pathways, called the tectofugal pathways, terminate in the medial and lateral regions of the ectostriatum. We propose to use stimuli that differ in their spatiotemporal properties to determine whether the medial and lateral regions of ectostriatum are functionally distinct regions. If a double dissociation can be obtained between lesions of medial ectostriatum and lateral ectostriatum using a test that combines high spatial frequency with a low temporal frequency versus a stimulus with a low spatial frequency at a high temporal frequency, we will have demonstrated two functional streams of visual processing that are comparable, at least in certain respects, with those of the primate visual system.

William Jeffery
The laboratory studies the evolution of developmental mechanisms. They use molecular, cellular, and genetic approaches to investigate embryonic development in two animal systems: ascidians and teleost fishes. The teleost Astyanax fasciatus is used to study the evolution of eye development. Astyanax populations living in surface streams are pigmented and have large eyes, whereas those adapted to limestone caves have lost their eyes and pigmentation. The surface and cave Astyanax diverged less than a million years ago. Thus Astyanax is one of the few cases in which the ancestral and derived developmental states are available for comparative analysis in the same species. Genetic studies indicate that many genes are responsible for loss of the eye during cavefish development, and that some of these genes may be different in isolated cave populations. Eye development is initiated in the cavefish embryo, however, the eye arrests later in development and disappears in the adult. They are studying the molecular basis of eye degeneration during cavefish development. They have shown that expression of the Pax-6 and Six-3 genes, which encode transcription factors with key roles in the eye, are modified in the cavefish eye primordium. They have also demonstrated that cavefish lens cells undergo extensive programmed cell death, presumably as a response to down-regulation of these, and other regulatory genes, which has widespread effects on eye development. Current studies are focused on identifying novel genes involved in eye degeneration in Astyanax and determining the effects of introducing functional copies of eye genes into the cavefish embryo.

Cynthia Moss
Dr. Moss's research program is directed at understanding auditory information processing and sensorimotor integration in vertebrates. In her lab, the echolocating bat serves as a model system for a neuroethologically-based study of hearing and perceptually-guided behavior. Work in the lab combines acoustical, psychophysical, perceptual, computational and neurophysiological studies, with the goal of developing integrative theories on brain-behavior relations in animal systems. Behavioral studies focus on the processing of dynamic acoustic signals for the perception of auditory scenes. The aims of this work are to develop a broad understanding of complex signal processing in biological systems and to establish an empirical foundation for integrative models of spatial information processing, the perceptual organization of sound, and adaptive motor behaviors. Neurophysiological studies examine how the brain processes sensory information and how this information is integrated with motor programs to permit perceptually-guided behavior. Current experiments focus on the functional organization of the bat's superior colliculus, a midbrain structure implicated in the coordination of multimodal sensory inputs and goal-directed motor behaviors. Recent results in the lab reveal distinct functional specializations in the superior colliculus that are important for the bat's acoustic orientation by sonar, and these data are used to develop a theoretical framework on the functional role of the mammalian midbrain.

Mary Ann Ottinger
Current research is focused on two areas: 1) the neuroendocrine basis for aging as it impacts reproduction and 2) the effects of endocrine disrupting chemicals on development and reproductive function in birds. In the first area, studies have concentrated on characterizing the process of aging in a Japanese quail model system. Our results have established that neuroendocrine changes that occur as the animal ages trigger a decline in all facets of reproductive function eventually leading to reproductive failure. Fundamental neuroendocrine alterations that accompany the process of aging are similar in mammals and in birds. These data have applications for extending reproductive life span in poultry as well as for captive propagation of threatened avian species. In the second focus area, understanding endocrine, neuroendocrine, and behavioral consequences of endocrine disrupter exposure in birds is critical, especially with the identification of sensitive stages in the life history. Studies are ongoing in the Japanese quail because this species is an excellent model for precocial avian species. Current studies build upon these data to assess the effects of several classes of endocrine disrupters, which have estrogenic activity on development and sexual differentiation.

Arthur Popper
Dr. Popper's research focuses on questions of comparative hearing in vertebrates, with particular interest in the structure and function of the auditory system of fishes. This work involves several different approaches to understanding how fish hear, and how the fish auditory system fits into the scheme of evolution of the vertebrate ear. Current investigations include behavioral investigations of hearing capabilities, mechanisms of sound source localization; and evolution of sensory hair cells in vertebrates. Recently, Dr. Popper and his group have demonstrated that some herring-like fishes can detect ultrasound and that this has evolved for the detection, and avoidance, of echolocating dolphins which are a major predator on these species. A major thrust of work in Dr. Popper's lab is to understand the mechanism of ultrasound detection and the general capabilities at these frequencies as compared to detection at lower frequencies.

Kerry Shaw
The focus of Shaw's research, to explain how new species evolve, involves three facets: the genetic boundaries between populations and species, the forces that promote diversification, and the evolution of behavioral and morphological traits. She studies the cricket genus Laupala, especially the features of mating systems such as acoustical communication and serial spermatophore production, the genetic basis of such traits, and historical replication of sexual selection, the probable cause of speciation. With 37 species endemic to the Hawaiian archipelago, Laupala offers an exceptional model to test hypotheses regarding the role o behavior in speciation.

Todd Troyer
The major focus of Troyer's lab is the development and refinement of bioinformatic tools that allow fine-grained, quantitative analyses of song development. These tools will be used to examine song learning in two closely related species of estrildid finches, focusing on interactions between syllable learning, sequence learning, and the development of the rhythmic structure characteristic of adult song. Analyzing data of this complexity requires the construction of functional models; machine learning and advanced statistical techniques will be used to evaluate the ability of competing models to account for the behavioral data. This behavioral modeling overlaps with the second focus of the lab, combining computational modeling and in vitro neurophysiology to explore the local circuit mechanisms underlying temporal behavior.

David Yager
Hearing in many insects is critical for finding mates, in interactions with competitors, and in detecting approaching predators. Dr. Yager's research focuses on the neuroethology of hearing in the praying mantis, an auditory cyclops with a single ear located in the ventral midline between the last pair of legs. One set of projects in the lab uses neurophysiological and anatomical techniques to study the peripheral and central neural components of this unique auditory system, particularly an identified, giant interneuron. Another goal of the lab is to use developmental and comparative techniques to determine the origin of the mantis ear, possibly as part of a very ancient mechanoreceptive system. How mantises use their hearing remains a puzzle. Because they hear only ultrasound, both lab and field projects are underway to look at interactions between mantises and hunting bats.

Research Interactions and Collaborations among Training Grant Faculty
Already established are numerous collaborations among faculty, students and postdocs in the Neuroethology Training Program. While some include participants in the Comparative and Evolutionary Biology of Hearing Training Program, there are many additional Neuroethology collaborations, and together, they bring exciting research and training opportunities to our graduate students and postdocs.