Richard D. Mooney - US grants

The overall goal of the proposed research is to determine the pathway(s) by which visual information is transmitted to the superior colliculus (SC) neurons that innervate nuclei which, in turn, control head and eye movements. The sensory information that deep layer, SC cells send to medullary and spinal structures is thought to be critically involved in orienting and attentional behavior. However, the visual input pathways for these SC neurons have not been defined. Previous physiological and light microscopic experiments have suggested several potential sources of critical visual input to deep layer output cells in the rodent SC. Superficially directed dendrites of deep layer neurons may receive retinal input and/or synapses from the axon collaterals of visually responsive superficial layer cells. Alternatively, direct retinal projections to the deep laminae and/or axonal projections from the superficial to the deep layers might provide the necessary visual input for these cells. We will combine anterograde transport, intracellular horseradish peroxidase injection, and electron microscopic techniques to determine which of these potential pathways actually exist in the hamster's SC. We will then combine electrophysiological recording with reversible inactivation techniques to determine which of the pathways defined in the electron microscope provide(s) the necessary visual input to deep layer output cells.

The overall goal of the proposed research is to determine the pathway(s) by which visual information is transmitted to the superior colliculus (SC) neurons that innervate nuclei which, in turn, control head and eye movements. The sensory information that deep layer, SC cells send to medullary and spinal structures is thought to be critically involved in orienting and attentional behavior. However, the visual input pathways for these SC neurons have not been defined. Previous physiological and light microscopic experiments have suggested several potential sources of critical visual input to deep layer output cells in the rodent SC. Superficially directed dendrites of deep layer neurons may receive retinal input and/or synapses from the axon collaterals of visually responsive superficial layer cells. Alternatively, direct retinal projections to the deep laminae and/or axonal projections from the superficial to the deep layers might provide the necessary visual input for these cells. We will combine anterograde transport, intracellular horseradish peroxidase injection, and electron microscopic techniques to determine which of these potential pathways actually exist in the hamster's SC. We will then combine electrophysiological recording with reversible inactivation techniques to determine which of the pathways defined in the electron microscope provide(s) the necessary visual input to deep layer output cells.

The overall goal of the proposed research is to determine the pathway(s) by which visual information is transmitted to the superior colliculus (SC) neurons that innervate nuclei which, in turn, control head and eye movements. The sensory information that deep layer, SC cells send to medullary and spinal structures is thought to be critically involved in orienting and attentional behavior. However, the visual input pathways for these SC neurons have not been defined. Previous physiological and light microscopic experiments have suggested several potential sources of critical visual input to deep layer output cells in the rodent SC. Superficially directed dendrites of deep layer neurons may receive retinal input and/or synapses from the axon collaterals of visually responsive superficial layer cells. Alternatively, direct retinal projections to the deep laminae and/or axonal projections from the superficial to the deep layers might provide the necessary visual input for these cells. We will combine anterograde transport, intracellular horseradish peroxidase injection, and electron microscopic techniques to determine which of these potential pathways actually exist in the hamster's SC. We will then combine electrophysiological recording with reversible inactivation techniques to determine which of the pathways defined in the electron microscope provide(s) the necessary visual input to deep layer output cells.

DESCRIPTION: (adapted from the applicant's abstract). A central goal of neurobiology is to identify the cellular mechanisms that enable animals to memorize novel stimuli and learn new behaviors. This project seeks to forge a link between the cellular and the behavioral aspects of learning by studying the synaptic properties of neurons within the avian brain that mediate the acquisition and production of learned songs. The goal of this study is to determine whether certain forms of long-lasting synaptic modification that can be observed in vitro provide the cellular mechanism for avian song learning. To further understand whether synaptic modification within the song system underlies avian vocal learning, experiments will test whether song system synapses can be strengthened through certain patterns of activation, whether this capacity is developmentally restricted, and whether acoustical isolation and castration, both of which lengthen the period of song learning, also lengthen the period in which synaptic modification can occur. This project will also examine the effects of acoustical isolation on the kinetics of N-methyl-D-aspartate(NMDA) receptor-mediated excitatory postsynaptic currents (EPSCs) within three forebrain song control nuclei, since NMDA receptors mediate several forms of synaptic plasticity within the vertebrate central nervous system, and because maturational changes in the kinetics of NMDA receptors are delayed in some developmentally plastic systems by sensory deprivation. Whole-cell voltage clamp recordings will be made in an in vitro brain slice to characterize the properties of NMDA-EPSCs within the song control circuit during development in both normal birds and in acoustical isolates. As a prelude to these experiments, the role of glutamatergic transmission in several forebrain song control nuclei will be described. A related set of experiments will examine the effects of steroid hormones on synaptic properties of the song system. Steroid hormones play a key role in ending vocal plasticity.Androgens "crystallize" song, transforming the structurally variable juvenile song to the acoustically stereotyped song of the adult. The final set of experiments will examine the effects of castration and androgen treatment on synaptic transmission within the song system, especially on NMDA receptor mediated transmission, and on the tonic level of inhibition, again using an in vitro brain slice preparation.

Our application's objective is to understand how the brain processes learned communication sounds. Auditory neurons in the avian song control nucleus HVc are highly selective for the bird's own song. This proposal seeks to discover the origins of song-selective auditory responses exhibited by HVc neurons. Three features of song-selectivity motivate the search for its neural substrate. First, song-selectivity arises through auditory experience. Therefore, finding where these responses first emerge within the songbird's brain will guide us to the site where auditory experience alters neural function. Second, song-selectivity affords a powerful system to examine the biophysics of combination sensitivity, a process relevant to the auditory processing of human speech. Third, song-selectivity is likely to facilitate song perception. In short, discovering the neural mechanisms of song selectivity can illuminate how auditory experience shapes behaviorally-relevant neural sensitivity to learned communication sounds. The specific aims seek 1) to discover the nature of local contributions to song-selectivity in HVc; 2) to determine whether extrinsic sources provide song- selective information to HVc; and 3) to locate these extrinsic sources, if they exist. In vivo intracellular recordings will be used to record from identified HVc neurons to reveal the pattern of subthreshold inputs underlying song-selective responses. Whether presynaptic neurons providing song-selective subthreshold input onto HVc neurons are local or extrinsic to HVc will be explored by reversibly inactivating the HVc local circuit, then measuring whether song-selective subthreshold responses persist. To localize extrinsic sources of song-selective input to HVc, we will use spike-triggered averaging techniques in vivo, and we will use focal glutamate stimulation and intracellular staining in vitro to better understand the source and function of monosynaptic inputs onto identified HVc neurons. In short, we will combine in vitro and in vivo techniques to address the origins of song-selective responses in HVc, with the aim of understanding learned communication.

These experiments address how respiratory and telencephalic afferents shape the activity of vocal motorneurons used for learned vocalizations. In those few vertebrate species where vocal learning occurs, such as humans and songbirds, the telencephalon plays a critical role in modulating respiratory- vocal interactions within the brainstem. In songbirds, a prominent role for the telencephalon in respiratory-vocal integration is suggested by a major projection from the nucleus robustus archistriatalis (RA), the sole output of the telencephalic vocal control network, to vocal (i.e., syringeal) motorneurons in the tracheosyringeal portion of the nucleus hypoglossus (NXIIts) and to medullary regions that house respiratory premotor neurons as well as neurons that project upon NXIIts. Songbirds constitute the system of choice in which to study how telencephalic activity influences respiratory-vocal integration, especially with respect to vocal learning, because: 1) avian song learning occurs during early development in a manner resembling human speech development, 2) the avian and mammalian brainstems are highly homologous and 3) unlike mammals, the vocal neuron pool is spatially separate from, rather than being embedded in, respiratory regions of the medulla. We propose to examine telencephalic-respiratory-vocal interactions at the cellular and synaptic levels. These intracellular electrophysiological and anatomical studies are essential because although much is now known about telencephalic and vocal muscular activity as it relates to birdsong, there remains a deficiency in our knowledge of the synaptic and intrinsic electrophysiology of syringeal motorneurons, especially with respect to their respiratory and telencephalic afferents. The collaborative effort proposed here will unite classical anatomical approaches with in vitro and in vivo intracellular electrophysiological techniques to 1) characterize the electrophysiological and morphological properties of vocal motor and respiratory neurons in the songbird, 2) directly search for the means by which respiratory-related neurons and vocal motor neurons synaptically interact and 3) examine the function of telencephalic inputs to syringeal motorneurons, and how these descending inputs both modulate and are gated by respiratory activity.

DESCRIPTION (provided by applicant): The long-term goal of this research is to analyze neural mechanisms that underlie vocal learning. The goals of this proposal are to understand both motor and auditory codes for learned vocalizations. This proposal relates to the R21 purpose by applying a new and highly innovative chronic recording method to study neural activity in a novel model species especially well suited to address the nature of auditory-vocal integration. Auditory-guided vocal learning, as occurs in humans and songbirds (but few other taxa), requires neural integration of auditory and vocal activity. One model for the neural basis for auditory-motor integration is that single neurons at the apex of the auditory-vocal motor pathway encode specific features of the vocal gesture and also respond to the resulting sound that this gesture elicits. This proposal seeks to study single neuron activity in the telencephalic nucleus HVc of the awake, behaving swamp sparrow, a songbird that produces several different vocalizations made up of categorically distinct elementary units (i.e., song notes) that are shared to varying degrees among the song types in an individual's vocal repertoire. The first Aim is to record the activity of individual identified HVc neurons in a swamp sparrow as it sings several song types, two or more of which share a note in common. The hypothesis to be tested is that HVc remotor neuron activity correlates with individual notes but not note sequences. The second Aim is to compare the activity of individual identified HVc neurons during singing and again, then the bird's various song and note types are played back to it through a speaker. The hypothesis to be tested is that for a single HVc premotor neuron the premotor activity and auditory response corresponds to the same common vocal unit (i.e., a note). This project also will provide pilot data for future experiments designed to study how premotor and auditory activity change during vocal learning, and to test the role of HVc's auditory activity in the perception of learned vocalizations. This project can help identify neural mechanisms important to audition guided vocal learning, and thus may yield insight into neural mechanisms for speech learning, perception and production.

DESCRIPTION (provided by applicant): Our objective is to analyze at the synaptic level how sensory and motor representations of learned vocalizations propagate and are transformed in basal ganglia pathways of the songbird. The songbird is an essential model for exploring auditory-vocal interactions akin to those underlying human speech, because birdsong and speech require auditory feedback and involve basal ganglia pathways. The songbird brain contains a well-defined circuit for singing and song learning, including a basal ganglia pathway essential to audition-dependent song plasticity and perception. An anatomically dedicated and electrophysiological identifiable pool of neurons in the pallial nucleus HVC (HVCx neurons) is the putative source of song-related auditory and motor activity in the basal ganglia pathway. Here we seek to explore how HVCx neurons synaptically signal their basal ganglia targets during singing and auditory presentation of the same song. This proposal's overarching goals are to test in adult songbirds whether: 1) inhibition onto HVCX neurons disinhibits the output of the basal ganglia pathway, 2) HVCx cells transmit temporally similar patterns of activity during singing and song playback, and 3) altered sensory feedback disrupts this sensory-motor similarity. The clinical significance of this proposal is two-fold. First, by using intracellular recordings in the anesthetized bird and extracellular recordings from identified neurons in the freely behaving animal, the proposed experiments will provide unusual insight into synaptic processing of behaviorally salient patterns of activity in basal ganglia pathways. Second, an increasing body of research including an analysis of heritable dyspraxias, stuttering, spontaneous vocalization in Tourette's syndrome and dysarthria in Parkinson's disease, points to an important role for the basal ganglia in human speech. Therefore, this research will illuminate generalized aspects of sensorimotor processing in the basal ganglia, while revealing specialized aspects of auditory-vocal processing in basal ganglia pathways important to vocal learning and maintenance.

[unreadable] DESCRIPTION (provided by applicant): A long-standing hypothesis holds that memory formation involves structural changes in synapses. Indirect evidence shows that dendrites, dendritic spines, and axons in the central nervous system can grow and retract under a variety of different conditions. Recent advances in imaging technology, such as multiphoton microscopy, have made it possible to directly image morphological changes in vitro and in vivo, but it has proven difficult to link these changes to the actual process of learning. This is due to the inaccessibility of brain areas involved in the learning process (such as the hippocampus) and to difficulties in identifying the synapses that are involved in learning. The overall aim of this proposal is to use the mouse olfactory system to determine whether changes in dendritic architecture accompany the formation of long-term memories. The formation of olfactory memories requires the olfactory bulb, whose location makes it very accessible for high-resolution imaging studies. Using genetically engineered mice in which specific neuronal populations are labeled with fluorescent markers, multiphoton imaging of neuronal dendrites over hours, days, and weeks will be used to determine the stability of dendrites in the adult brain. Animals will then learn an odorant discrimination task, and imaging will be used to investigate the extent to which learning the task results in dendritic alterations. To begin to address possible mechanisms involved in dendritic remodeling, a preparation will be developed in which learning can be induced while animals are anesthetized, which will allow real-time observations and manipulations of circuits in the bulb. These experiments will determine whether structural changes are a requisite for long-term memories. Understanding the cellular changes that accompany the formation of memories is critical for understanding how normal memory formation takes place, and in uncovering mechanisms that can be targeted for intervention in the many disorders of memory, both in normal aging and in pathological conditions such as Alzheimer's disease. [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): The ability to detect and interpret communicative vocalizations is fundamental to human interaction. Identifying brain circuits and mechanisms that support vocal perception is essential for treatment of the broad array of pathologies that affect speech comprehension, such as aphasic stroke, autism and developmental dyslexia. Most of these conditions involve damage or dysfunction in the auditory cortex, indicating that this structure plays an essential role in vocal perception. Disappointingly, the cortical circuit mechanisms that underlie the perception of communicative vocalizations and the role of auditory cortex in selecting appropriate behavioral responses remain enigmatic. The goal of this proposal is to integrate optogenetic, electrophysiological and behavioral methods to resolve the synaptic properties of cortical circuits that enable vocal recognition and to test the role of the auditory cortex in mediating auditory-guided behavior. This goal requires a model animal that relies on vocal communication, is suitable for high-resolution electrophysiological analysis of neural circuitry, and is amenable to genetic tools for manipulating brain activity. Mice are highly social mammals that use vocalizations to communicate, and are accessible to cutting edge techniques for precisely dissecting the synaptic organization and function of the auditory cortex. Female mice are selectively drawn towards cries of isolated pups, simplifying assessment of vocal perception and its relation to neural activity. Moreover, the mouse auditory cortex contains a region (UF) specialized for the detection of sounds in the acoustic frequency range of pup cries, thus narrowing the search for vocal perception circuitry. Despite these critical advantages, little is known about the functional synaptic properties of the mouse auditory cortex and how these properties serve vocal recognition. Our proposal takes advantage of newly created lines of genetically modified mice that express a light-sensitive ion channel in restricted subsets of cortical neurons. Expression of this channel protein allows one to precisely manipulate neural activity, and thus to ascertain detailed synaptic connections between UF and surrounding auditory cortical regions that we hypothesize may support vocal recognition. Furthermore, we will functionally assess whether activity in the UF circuit is necessary and sufficient for releasing vocalization-evoked locomotor behavior in female mice. This approach to examining the mechanisms of vocal perception in the mouse model offers several crucial benefits that extend well beyond the scope of the biology of vocal communication in mice, and are directly relevant to the concept of the R21 mechanism specifically and NIH's health mission generally. First, the proposal features the development of innovative approaches to probing cortical circuitry that will be readily applicable to a wide range of systems. Second, because the mouse cortex shares much of its cell type diversity and basic synaptic microcircuitry with the human cortex, our results are almost certain to reveal general principles of auditory spectral integration that will directly enrich our understanding of human auditory cortical function. Finally, development of a mouse model of social vocal communication will open new avenues of research for our group as well as many others, allowing analysis of how genetic disorders that alter cortical synaptic architecture interfere with social cognition and communication. Identifying the neural mechanisms that support vocal perception is germane to treatment of pathologies that affect speech comprehension, such as aphasic stroke, autism and developmental dyslexia. The auditory cortex plays an essential role in vocal perception, but the cortical mechanisms that underlie vocal recognition and the role of cortical circuits in auditory-guided behavior remain unresolved. Therefore, this proposal's goal is to develop and integrate genetic, electrophysiological and behavioral approaches in mice to assess how synaptic circuits in auditory cortex enable vocal recognition and to test their role in mediating auditory-guided behavior. [unreadable] [unreadable] [unreadable]

For many vertebrate animals, the capacity to learn certain skills is greatly enhanced during a time in juvenile life referred to as a sensitive period. What happens to the juvenile brain as the young animal learns a new skill? Conversely, what properties of the juvenile's brain favor learning? This project seeks answers to these questions. The goal of this project is to use a high resolution, laser-powered microscope to visualize individual nerve cells in the brain of a living songbird. The nerve cells to be imaged play an important role in singing, a vocal behavior that resembles human speech in that both are products of imitative learning. By re-imaging the same nerve cell over hours, days and even weeks, and precisely monitoring the vocal learning process, the investigator will examine whether vocal learning involves structural changes at the connections, or synapses, linking together these nerve cells. The investigator predicts that synapses will be less stable at the onset of the sensitive period but that they will rapidly stabilize as the bird begins to imitate the song of another bird. The significance of this project is three-fold. First, it can assess whether enhanced structural plasticity characterizes sensitive periods for learning. Second, it can identify the structural changes that occur during the learning of a complex vocal behavior. Third, it will train young scientists in cutting edge experimental methods at the high school, doctoral and postdoctoral level.

DESCRIPTION (provided by applicant): Sensory feedback - sensory activity generated in response to one's own movements - enables us to learn complex athletic and musical skills. Sensory feedback also enables learning of complex social skills, including speech, language and other culturally transmitted behaviors. In addition to sensory feedback, the cultural transmission of behavior depends on sensory experience of a behavioral model afforded by another individual. Despite the central importance of culturally transmitted behaviors to normal human function, how these two types of experience act in the brain to enable behavioral learning remains poorly understood. The overarching aim of this proposal is to use high resolution imaging methods combined with genetic and physiological methods to study how experience of a behavioral model and sensory feedback affect the properties of neural circuits essential to the learning and execution of complex, culturally transmitted motor sequences. The significance of the proposed research to the NIH mission is four fold. First, this research is relevant to understanding how electrical stimulation and genetic methods can be used to manipulate sensory feedback signals important to learned behaviors. Second, this research can improve our understanding of how loss of sensory input affects the function of sensorimotor circuits that control learned behaviors. Third, these studies can inform the design of artificial neural circuits that in the future are likely to provide a therapeutic avenue to restore brain function. Fourth, by examining the effects of instructive experience on sensorimotor circuits in the naive juvenile, these studies can identify features of the developing nervous system that facilitate learning.

DESCRIPTION (provided by applicant): The action potentials measured by an extracellular electrode are the tip of a computational iceberg, beneath which operates a vast electrochemical signaling system involving fast neurotransmitters, neuromodulators, hormones, the receptors that bind these signaling molecules, and the intrinsic membrane properties of the neurons in which these receptors reside. Consequently, the extracellular electrodes commonly used to study neural activity in freely behaving animals are blind to a wide spectrum of brain activity. This insensitivity limits our understanding of the neural mechanisms underlying normal brain function and also limits insights into disordered neural activity that underlies neurological and neuropsychiatric diseases. Surmounting this limitation requires technology that can overcome the formidable challenge of obtaining intracellular recordings from neurons in the brain of a freely behaving animal. This proposal seeks to overcome this challenge by accomplishing three Specific Aims: 1) To develop a miniature microdrive in which the intracellular electrode can be rapidly loaded and flexibly positioned over the brain surface. 2) To miniaturize the size and mass of the drive so that a mouse can readily carry at least two devices, facilitating an assessment of functional connectivity between neurons and brain areas. 3) To make intracelular recordings in the auditory cortex of freely behaving mice as they process auditory stimuli in conditions that are known to strongly modulate auditory responses. The refinement of this technology will be widely beneficial to the neuroscience community and its application in the mouse will open the door to analyzing how disordered neural activity underlies diseases. ! PUBLIC HEALTH RELEVANCE: This proposal seeks to develop a miniature intracellular recording device that can be used to make highly sensitive recordings of neural activity in freely moving animals. Development of this technology can provide a powerful tool for elucidating neuronal activity that enables normal brain function and disordered neuronal activity underlying diseases. !

Some of the most remarkable behaviors, including speech, musical, and athletic performance, depend on the brain's ability to precisely represent and control the timing and order of elementary movements. How the brain accomplishes this feat is largely unknown. This project will identify how the brain encodes the vocal elements and sequences used in learned vocal communication. To accomplish this goal, state of the art high-resolution optical imaging and electrical recording methods will be used to measure neural activity in animals as they engage in vocal learning and communication. This project will determine how populations of interconnected neurons that are necessary to vocal communication encode vocal elements and sequences. Accomplishing this goal is essential to understanding the neural basis of communication and also has other important potential benefits, including the ability to diagnose and ultimately repair brain pathologies that impair perception or movement, and to design machines that emulate these processes. This project will advance our understanding of neural mechanisms that enable the production and perception of complex, sequential behaviors, train professional scientists at the doctoral and postdoctoral levels, and enrich the science curriculum of high school students both locally and nationally.

The intellectual merit of this project is that it will shed light into fundamental cellular processes by which the brain encodes complex learned behaviors. This project's goal is to understand how the brain encodes syllables and syllable sequences in birdsong, a complex learned vocal behavior. The study will focus on how syllables are represented by spatiotemporal patterns of activity in populations of sensorimotor neurons important to vocal communication. Resolving this problem is an essential step to understand the neural basis of vocal communication. This project blends leading edge methods, including multiphoton calcium imaging of neuronal population activity and intracellular recordings and genetic manipulations in singing birds, to explore the synaptic, cellular, and circuit mechanisms that encode learned vocalizations. Until now, it has been impractical to interrogate how the brain encodes sensory and motor representations of such complex behaviors with cellular and synaptic resolution.

DESCRIPTION (provided by applicant): Auditory sensations reflect a mixture of self-generated sounds, such as those created when we speak or play a musical instrument, and sounds arising from other sources, such as a blaring siren. Distinguishing between these two classes of stimuli is a major challenge that the auditory system must overcome to generate stable auditory percepts and facilitate auditory-guided behaviors. Evidence from a wide variety of sensory systems, including the auditory system, indicates that harnessing a copy of a motor command signal to modulate sensory processing in a movement-dependent manner facilitates this distinction. Although such motor-sensory interactions are widespread in the auditory system, motor cortical modulation of auditory cortical activity is thought to be important to higher-order auditory function necessary to communication. Moreover, dysfunction of cortical corollary discharge machinery is speculated to underlie auditory hallucinations characteristic of psychoses. Despite their postulated role in normal and disordered audition, the synaptic and circuit mechanisms underlying interactions between the motor and auditory cortices remain enigmatic. Here we propose to integrate genetic, synaptic, circuit, and behavioral methods in the mouse to map the structure and function of circuits that convey motor-related signals to the auditory cortex and to test the role of these circuits in auditory cortical processing. The propose experiments will delineate the structural and functional properties of cortical circuitry that facilitates normal auditory function during self- generated movements, including vocalization. The significance of the proposed research to the NIH mission is four-fold. First, this research can inform how the nervous system mediates normal hearing during self- generated movements; this ability is essential to speech comprehension and learning, and also is fundamental to the learning and execution of complex skills, including musical performance. Second, dysfunction of this motor to auditory interaction at the cortical level is thought to drive auditory hallucinations; a synaptic characterization of this interaction is a necessary step to understand the genesis of these pathologies and to ultimately design appropriate therapies. Third, an understanding of how motor circuits modulate hearing may provide insights into how these circuits can be manipulated either through perceptual training or direct manipulation of neural activity to facilitate auditory comprehension in the face of hearing loss. Fourth, analyzing the properties of these corollary discharge circuits in the absence of hearing, as also proposed here, can provide insights into how the brain reorganizes in response to deafness.

Neurons in the ventral tegmental area (VTA) play a key role in motor learning, and neurological diseases that affect VTA neurons or their targets in the basal ganglia (BG) severely disrupt behavior. Notably, much of our understanding of how the VTA functions in motor learning has relied on paradigms that employ external reward or punishment and involve relatively slow and simple behaviors, such as lever pressing or licking. In contrast, many of our most complex and valued behaviors, such as speech and musical expression, can be learned without external reinforcement, suggesting that their learning is internally reinforced. Further, internally reinforced behaviors such as speech or musicianship require highly complex and rapid motor sequences and are more readily acquired during juvenile sensitive periods. How the VTA interacts with the BG to mediate complex forms of internally and externally reinforced auditory-motor learning remains unknown. Here we propose to identify how the VTA and BG interact to mediate different forms of auditory-motor learning using a novel combination of intersectional genetic methods to selectively ablate VTA neurons, microdialysis, calcium imaging and optogenetic manipulation of VTA terminals and BG neurons combined with rapid and temporally precise behavioral manipulations. These approaches will be used to test the hypothesis that the VTA functions as a ?critic? that evaluates auditory feedback and instructively modifies BG premotor activity, which in turn drives internally and externally reinforced auditory- motor learning. Resolving how VTA-BG circuits mediate these forms of learning are critical issues for understanding motor plasticity in health and disease. In fact, speech pathologies typify various diseases that affect VTA-BG circuitry, while mutations that disrupt dopamine-mediated signaling in the BG also impair vocal learning. Therefore, the proposed research can shed light on the neural circuit mechanisms that enable complex internally and externally reinforced behavioral learning while also revealing how dysfunction in these circuits interferes with the learning and execution of communicative behaviors.

Project Summary An inability to form and maintain social bonds typifies a wide range of neuropsychiatric and neurodevelopmental disorders. These social deficits stem in large part from impaired expressive and receptive vocal communication skills. Surprisingly, exactly how vocal communication promotes social affiliation is not well understood, in part because the underlying neural circuits remain poorly described. Here we propose the use of a novel genetic approach to selectively tag neurons that are active during social encounters that elicit vocalizations. We will combine this innovative method with in vivo imaging, electrophysiology, chemical and optogenetic perturbations of neural activity, and behavioral measurements to identify neural circuits that facilitate expressive and receptive aspects of vocal communication in the service of social affiliation. In Aim 1, we will test the idea that a specific subpopulation of neurons in the midbrain periaqueductal gray (PAG) is required for male and female mice to produce vocalizations used during their social interactions. In Aim 2, we will manipulate the activity of these PAG neurons to suppress or augment vocalization, allowing us to test the idea that these vocalizations promote social affiliation. In Aim 3, we will test the idea that prefrontal cortical (PFC) neurons that provide input to PAG vocalization neurons are important in regulating vocalization as a function of social context. In Aim 4, we will either reversibly silence or image PFC neurons that provide input to the PAG to test the idea that they play a role in generating affiliative social responses in males and females listening to a vocalizing individual. These studies will identify the neurons and circuits that gate vocalization during social encounters and promote social affiliation in response to these acoustic signals. This research will also build the foundation for future studies that explore how these circuits are affected in mouse models of neuropsychiatric disorders characterized by social communication and affiliation deficits, such as autism spectrum disorder and schizophrenia.

Abstract This application seeks support for early stage training of doctoral students in the neurosciences at Duke University. The goal of this comprehensive, broad-based, interdisciplinary Neurobiology Training Program (NBTP) is to train top-level neurobiologists for research-oriented positions in academia, industry, and related arenas. The application seeks funding for 6 predoctoral trainees each year, typically 3 in their first year and 3 in their second year. Richard Mooney, PhD directs the program in concert with the NBTP Steering Committee comprising select faculty and students. Preceptors are drawn from many departments across the School of Medicine, the School of Engineering and the College of Arts and Sciences and represent a broad diversity of fields including molecular, cellular, circuits, systems, computational, translational and cognitive neuroscience. Preceptors include scientists with long and distinguished records of achievement as well as recently recruited, talented young faculty. A large applicant pool - approaching close to 200 candidates per year - permits recruitment of a talented, diverse class of ~7 new students each fall. Close to half of the matriculants will be supported in their first two years by the Duke Graduate School, which enables the program to pull from international as well as domestic pools. Students undergo extensive training including demanding coursework addressing the depth and breadth of fundamental and translational neuroscience, including experimental design, technical implementation, data analysis, and interpretation. Required course work emphasizes molecular and cellular neuroscience; circuits and systems neuroscience; the neurobiology of disease; quantitative, statistical and computational neuroscience methods; scientific writing; written and oral presentation; teaching and career development. Their thesis committees and the Program Steering Committee carefully monitor students' progress throughout the entire period of graduate training. Students in our program are expected to obtain their doctoral degree within 5 to 6 years and to publish original research articles stemming from their doctoral studies. Upon completion of postdoctoral fellowships and clinical training (where applicable), we expect that our graduates will secure tenure-track faculty positions in research institutions, obtain neuroscience-related jobs in industry, use their neuroscience training to practice medicine, and teach and train the next generation of neuroscientists at the graduate and undergraduate levels. The Training Program makes extensive efforts to recruit and retain students from underrepresented groups. The goal of the program is to train a new and diverse generation of scientists equipped with the knowledge, imagination and insight needed to cross disciplinary boundaries in search of a new and deeper understanding of the basis of nervous system function in health and disease.