The brain is a remarkably complex network of neurons, and many functions and dysfunctions of the mind cannot be localized to any particular part of the brain. Further, network activity changes in time at every spatial scale, from molecular dynamics of single synapses to coordinated oscillations across brain areas to circadian rhythms. Distilling spatial-temporal coherent patterns from large scale, noisy measurements is vital to understanding how networks of neurons give rise to behavior.
I am inspired by system-level questions in neuroscience: How can we describe the multi-scale connective topology of brain areas? What functional metrics differentiate a neuronal network before and after learning? To tackle these and related questions, I leverage recent mathematical advances in the fields of dimensionality reduction and compressive sensing.
I am interested in the mechanisms by which cells respond to the extracellular signals as well as the influence of their three dimensional arrangement. Previously, I was involving in the research of tissue engineering of smooth muscle sheet in blood vessels, tissue engineering of cartilage in gelatin/chondroitin sulphate/hyaluronan modified tricopolymer scaffold, and the dose dependent effects of small molecules on porcine chondrocytes. Currently, I am emphasizing on scaling of dendrite arbors and its coordination with underlying substrate in Drosophila sensory neurons.
Animals collect and act on spatially and temporally rich sensory information to move through complex natural environments. My research uses insect flight as a model to understand the role of sensorimotor processing in the control of animal movement. Specifically, I focus on how the nervous system extracts information about an animal’s body dynamics in controlling neuromuscular programs that accomplish agile maneuvers. An open challenge is how these animals detect the dynamics of their own bodies in addition to external sensory cues. In this regard, I am focusing on inertial and gyroscopic sensing in insect flight. I am studying how a flying insect uses this information to produce behavior robust to external disturbances through the interaction between the neurobiology of sensors embedded in sensory structures and the structure’s biomechanics. Achieving a comprehensive understanding of this problem by its very nature requires an interdisciplinary approach, and I use a combination of engineering, neuroscience, and behavioral techniques to address these questions.
Neuroethology and the Role of Chemical Communication
Chemical communication is the oldest sensory system and underlies nearly every critical ecological and evolutionary interaction. My research interests are in chemosensory physiology and ecology, which pertains to understanding the influence of chemical signals on ecological interactions, and the neural basis of behavior. From the spatial scale of a sperm cell, to that of a macroorganism, the ability to locate the source of a chemical cue mediates many fundamental biological processes.
I am broadly interested in understanding the genetic basis of evolutionary processes, specifically the generation and maintenance of phenotypic variation and the maintenance of reproductive isolation during secondary contact between sister species.
My current work focuses on investigating pollinator-mediated reproductive isolation between two species of Mimulus wildflowers native to the Sierra Nevada mountains of California. I am specifically looking at the effect of pigmentation and scent on attraction and visitation by hawkmoths (Sphingidae), which are known to pollinate one species of Mimulus in California (Mimulus aurantiacus).
My research group focuses on the function and the development of song. Our study species is the song sparrow. We study function in the field, via a long-term banding, recording and radio-tracking program combined with field experiments (mostly playback studies). We study development both in the field, where we focus on young males we have banded in the nest or netted during their first summer, and in the laboratory, where we attempt to recreate the key conditions identified in the field studies. Our laboratory song-learning studies use multiple live
Vocal learning in songbirds is an experimentally accessible model system in which to study the neural mechanisms of learning. Juvenile birds memorize song(s) from an adult tutor and then use auditory feedback from their own songs to compare with their memory of the tutor song(s). This comparison guides a process of motor learning; through practice, juvenile birds gradually learn to produce a highly stereotyped song that resembles the tutor song. Extensive research has investigated the underlying neural circuits that are involved in song learning and production. Our lab uses a variety of electrophysiological, anatomical and behavioral approaches to probe the neural mechanisms that mediate song learning and song behavior.
Two main neural circuits have been implicated in song production and learning. The motor pathway descends from forebrain nucleus HVC, which projects to nucleus RA, which then projects to brainstem motor and premotor neurons controlling muscles of the vocal organ, the syrinx, and those of respiration. This pathway is essential for production of song. A second circuit, the anterior forebrain pathway (AFP), arises from HVC as well and projects to the basal ganglia structure area X, which projects to the thalamic nucleus DLM, which projects to a forebrain nucleus LMAN, which projects back to motor pathway nucleus RA. The AFP is essential for vocal learning but not production of previously learned song. Neurons of the AFP exhibit specific responsiveness to auditory information and are therefore well placed to provide the motor pathway with auditory feedback about the quality of the bird's own song.
Our main long-term goal is to understand at the level of neurons, synapses and circuits how song is learned and produced. Our current work falls into several categories:
- Mechanisms of pattern generation in the motor pathway
- Structure and function of the anterior forebrain pathway
- Evolutionary origin of the anterior forebrain pathway in songbirds
- Mechanisms underlying seasonal control of song (in collaboration with Eliot Brenowitz)
Neurons and neuronal networks decide, remember, modulate, and control an animal¹s every sensation, thought, movement, and act. The intimate details of this network, including the dynamical properties of individual and populations of neurons, give a nervous system the power to control a wide array of behavioral functions. We want to know more about neuronal dynamics and networks; about synaptic interactions between neurons; about how neuronal signaling and behavior and control and environmental stimuli are inextricably linked.
My research involves the integration between mechanism and function in animal behavior, with an emphasis on acoustic communication in birds and frogs. The principal current focus is on the song control system in the brains of songbirds. I emphasize a comparative, evolutionary approach to this system, and combine behavioral studies in the field with laboratory techniques in neuroendocrinology, neuroanatomy, molecular biology, and signal analysis. I am currently pursuing three major topics of study in the song system. One concerns the physiological and molecular mechanisms, and the behavioral consequences, of seasonal plasticity observed in the morphology of song regions of the brain. A second topic concerns the recruitment of new neurons to a song nucleus in the forebrain of adult birds, studied from the perspective of its physiological regulation and the influence of environmental factors. The third topic relates to the observation that neurons in song control nuclei receive input from auditory regions, and respond selectively to the presentation of conspecific song. I am investigating the role of song nuclei in the behavioral recognition of conspecific song in the contexts of mate choice and territorial defense.