Ann M. Graybiel - US grants

Many fundamental issues in developing neurobiology relate to the origins and maintenance of modular patterning in the nervous system. Both in the hindbrain and in the forebrain, regulation of multicellular compartments are being found to play an essential role in development and pattern formation. The striatum, the largest subcortical structure of the mammalian forebrain, offers a promising system for studying compartment formation in the forebrain. It contains neurochemically distinct macroscopic compartments, striosomes and matrix, that have different schedules of neurogenesis, connection formation and transmitter-related neurochemical specification. Determining the mechanisms underlying the formation of these striosome/matrix compartments is the core issue addressed by most of the experiments proposed. We propose to test hypotheses about the roles of selective cell-cell adhesion, striatal connection formation, and local antigen expression in the formation of striatal compartments. These experiments will involve some normative studies of developmental marker expression, but most will employ neuronal grafting and organotypic slice cultures. Together, these experiments should not only help to identify conditions leading to compartment formation in the striatum but also help to establish model in vivo and in vitro systems with which the molecular events underlying compartment formation can be identified.

Multiple visual pathways reach the thalamus and cortex in mammals, including primates, and a large set of cortical visual areas together comprise a sizable fraction of the neocortical mantle. In the proposed research we intend to use neuroanatomical tracer methods, histochemistry including immunohistochemistry, ligand binding and lesion techniques in order to achieve four goals. First we propose to determine the main patterns of connectivity of the striate and extrastriate cortical area using the cat as a "model preparation" because of the ease of identifying connectionally distinct extrageniculate thalamic subdivisions by acetylcholinesterase histochemistry and the consequent ease of referring the connections found to know organizations of thalamo-corticothalamic connections. The second goal of the proposed work is to determine whether the cholinesterase activity patterns in the extrageniculate and geniculate thalamic nuclei are indicative of cholinergic pathways, using ligand binding and immunohistochemical methods and lesions and, with the collaboration of Dr. Roffler-Tarlov, biochemical assays of choline acetyltransferase and acetylcholinesterase activity. The third goal is to explore the distribution of cholinesterases in the geniculostriate and extrageniculostriate visual system of Macaque monkeys following on our preliminary observation of discrete laminar and compartmental localization of these enzymes in the lateral geniculate body, striate cortex, pulvinar and extrastriate cortex. We propose to determine further whether these histochemically distinct compartments can be seen in human autopsy specimens of thalamus and cortex, which would provide a natural and direct bridge between the proposed experimental work and work on human brains in health and disease.

The work proposed focuses on interrelated regions of the basal ganglia (striatum and pallidum) and substantia nigra. Diseases of the basal ganglia are debilitating and are associated not only with motor dysfunctions but also cognitive-affective symptoms. The main goal of the proposed work is to gain an understanding of the functional organization of the basal ganglia and its dopamine- containing input systems in the primate and to relate findings from experiments on normal and MPTP-treated primates to observations on postmortem human brains from normal individuals and from persons who suffered premortem extrapyramidal disorders such as Parkinson's disease, progressive supranuclear palsy and Huntington's disease. Experiments are proposed to study the distribution of neurotransmitter-related compounds in the striatum, pallidum and substantia nigra and to relate the chemoarchitecture of these regions to their input-output connections. Special emphasis is to be placed upon the cholinergic and dopaminergic mechanisms of the basal ganglia, on the neuropeptide-containing elements there, and on neuroleptic- related sigma receptor sites insofar as they are related to the dopamine-containing nuclei of the midbrain. Studies are planned to extend these observations by monitoring the effects of in vivo pharmacological manipulations. By coordinating observations in monkey and human, it is hoped that significant progress can be made toward an understanding of the basal ganglia in health and disease.

The work proposed focuses on interrelated regions of the basal ganglia (striatum and pallidum) and substantia nigra. Diseases of the basal ganglia are debilitating and are associated not only with motor dysfunctions but also cognitive-affective symptoms. The main goal of the proposed work is to gain an understanding of the functional organization of the basal ganglia and its dopamine- containing input systems in the primate and to relate findings from experiments on normal and MPTP-treated primates to observations on postmortem human brains from normal individuals and from persons who suffered premortem extrapyramidal disorders such as Parkinson's disease, progressive supranuclear palsy and Huntington's disease. Experiments are proposed to study the distribution of neurotransmitter-related compounds in the striatum, pallidum and substantia nigra and to relate the chemoarchitecture of these regions to their input-output connections. Special emphasis is to be placed upon the cholinergic and dopaminergic mechanisms of the basal ganglia, on the neuropeptide-containing elements there, and on neuroleptic- related sigma receptor sites insofar as they are related to the dopamine-containing nuclei of the midbrain. Studies are planned to extend these observations by monitoring the effects of in vivo pharmacological manipulations. By coordinating observations in monkey and human, it is hoped that significant progress can be made toward an understanding of the basal ganglia in health and disease.

Experiments based on physiologically-guided anatomy in the primate are proposed to help define how cortex related to visuo-oculomotor processing projects to basal ganglia, and how the main output from the basal ganglia to the superior colliculus (the nigrotectal pathway) is integrated with projections to the colliculus from the same areas of cortex. For the eye-movement related cortex, emphasis will be placed on comparing the connections of the classic prearcuate frontal eye field with those of the newly discovered supplementary eye field. We also propose to test whether inferior parietal cortex overlaps with the eye field projections. For the visual cortex, emphasis will be placed on discovering whether areas MT and V4 of the visual cortex project to the same or separate parts of the striatum and superior colliculus. The mosaic structure of the targets of these cortical outputs may be crucial to the further integration as well as to the segregation of these information lines. This issue will be studied by mapping the patchy inputs especially from the eye-field cortical areas and from MT and V4 of extrastriate cortex in relation to each other both in the matrix of the striatum and in the intermediate gray layer of the superior colliculus. The possibility that spatially distant parts of visuo-oculomotor related cortex project to nearby parts of the basal ganglia and superior colliculus thus will be tested. The ultimate goal of this work is to lay the foundation for an understanding of the role of the basal ganglia in visuo-oculomotor processing.

DESCRIPTION: (Applicant's Abstract) Chronic exposure to psychomotor stimulants produces long-term changes in behavior including addiction and sensitized responses to further drug exposure. There is a great need to understand the changes in the central nervous system that occur with repeated drug exposure. A large body of evidence has implicated the striatum (caudoputamen and nucleus accumbens) in these brain effects, together with the midbrain dopamine systems that innervate the striatum. An interesting recent series of studies has demonstrated that exposure to psychomotor stimulants can produce striking effects on the expression of a series of immediate early genes (IEGs) that code for transcription factors. These experimental data are interesting because changes in transcription factor expression could have long-term effects on neuronal function. We propose a series of interrelated experiments to study these changes in expression. We propose to test specific hypotheses under three Aims. In Aim 1, we propose to test the hypothesis that chronic intermittent exposure to cocaine and amphetamine leads to long-term changes in the inducibility of IEGs in the striatum and that these involve down-regulation of IEG expression in the matrix relative to the striosome (patch) compartment. This hypothesis is based directly on preliminary experiments showing increased patchiness in striatal IEG expression following chronic intermittent exposure. To test for long-term effects, IEG expression after prolonged withdrawal periods will also be examined. In Aim 2, we will test the hypothesis that changes in dopamine receptor sensitivity occur with chronic exposure, that glutamate receptor function also is important for changes in IEG expression, and that IEG expression after cocaine and amphetamine treatment will show cross-sensitization. Finally, in Aim 3 we will test the hypothesis that drug-selective IEG expression patterns induced in the striatum by acute cocaine and amphetamine will be present in the squirrel monkey striatum, with amphetamine inducing a striosome-predominant pattern relative to cocaine. Taken together, these experiments will provide critical new data on the systems-level molecular change occurring in the striatum in response to chronic psychomotor stimulant exposure, on the duration of these changes, and on the receptor systems involved in producing these changes. In addition, these experiments will provide new and much-needed data on molecular responses to these drugs in acutely treated non human primates, a critical bridge toward understanding their effects in humans.

DESCRIPTION (Investigator's Abstract): Dysfunctions of the basal ganglia have been implicated in extrapyramidal movement disorders such as Parkinson's disease and Huntington's disease, and the basal ganglia are abnormal in some neuropsyctuatric disorders as well. No clear idea has yet emerged, however, about what neural operations are performed in the basal ganglia. Strong evidence suggests that the functions of the basal ganglia must depend heavily on their cortical inputs, because the neocortex provides most of the inputs that the basal ganglia receive. These inputs enter mainly by way of corticostriatal projections to the striatum, and indirectly via the thalamus. The largest outputs of the basal ganglia in turn link these nuclei, through series of synaptic steps, to the motor, promotor and prefrontal cortex. The basal ganglia thus appear. to receive cortical input, process it under the influence of modulatory inputs (for example dopaminergic) and return it to the frontal lobes (and to some brainstem sites). We propose a coordinated series of experiments in monkeys and rats to study cortical-based ganglia linkages. Specifically, we propose to analyze in detail the sensorimotor cortical projections to the striatum. This sensorimotor system has significant advantages for study: the inputs are strong, they can be identified electrophysiologically by recording and microstimulation in the cortex, they can be mapped rigorously with sensitive tracer methods, and they thus can be analyzed in depth to permit stud of the map-transformations that occur between cortex and striatum. Much of the proposed work on this system (AIMS 1,2 and 4) is to be in squirrel monkey, in which we and others have found a distributed, catchy organization of inputs from primary somatosensory and motor cortex to the putamen. We will attempt to determine the rules of organization of these distributed and modular sensorimotor inputs. A series of studies is also proposed in the rat to attempt delineation of striatal cells activated by the sensorimotor cortex. In these experiments we propose (in AIM 3, with follow-up in the squirrel monkey in AIM 4) to use electrical and chemical stimulation of sensorimotor cortex to activate immediatearly genes in striatal neurons. The gene expression will be used as a cellular-level readout of neural ensembles activated by cortical input in the striatum and its output targets, and the pathways necessary for this activation will be determined. With these two complimentary techniques, our goal is to delineate the organization of corticostriatal sensorimotor maps in sufficient detail to gain insight into the functions of the striatum. The significance of this work is twofold. First, it may help uncover the neural substrates of focal and somatotypically distributed banal ganglia movement disorders. Second, it should help identifying what transformations occur in cortical-basal ganglia loops.

DESCRIPTION (Adapted from applicant's abstract): The striatum is a subcortical structure that is heavily interconnected with the neocortex and that is thought to function in relation to sensorimotor learning, motivation action planning, and habit formation. Neural processing in the striatum is also thought to influence cognitive functions of the frontal lobes, because the main cortically-directed outputs of the striatum lead to the frontal cortex. Prior anatomical work has shown that the striatum has a modular anatomical architecture. The hypothesis to be tested is that the striatum also has a modular functional architecture that can be detected with state-of-the-art ensemble recording methods. The goals of the proposed work are (1) to use tetrode technology to record ensemble activity from the striatum of rats as they perform behavioral tasks designed to engage striatal networks; and (2) to analyze the population neuronal activity recorded to determine whether striatal networks show spatiotemporal patterns of activity and whether these change dynamically as the animals learn. It is hypothesized that patterns of coherent task-related activation will appear across groups of neurons recorded by single tetrodes within a ca. 100 um diameter and groups of neurons recorded by multiple tetrodes separated by 400-500 um. This range of recording space should allow monitoring of neural activity in single anatomical modules (ca. 200-300 um) and across adjoining anatomical modules. It is further hypothesized that task-related activity patterns will change with learning and that additional patterns may appear as animals learn striatum-based tasks. The ultimate objective of this work on the spatiotemporal dynamics of neuronal activity in the striatum is to understand the role of striatal activity in cortico-basal ganglia loop function. This research has potential significance for understanding network activity of complex circuits in a major subcortical structure. This research also has potential significance for clinical work in that it should provide basic science insights into the neural basis of motor and cognitive functions that are disabled in cortico-basal ganglia disorders.

The experiments proposed have as their goal combining gene-based and neurobiology-based methods to advance understanding of the fundamental neurobiology of the nigrostriatal system and its particular disruption in Parkinson's disease. Our proposed approach is to develop and implement studies of striatal ensemble activity in the mouse, with the immediate aim of studying transgenic mice generated by our colleagues in the Center, and with the long-term goal of taking advantage of the extraordinary opportunities to examine the fundamental molecular and neurologic bases of parkinsonian disorders by studying mice reengineered to over or under express genes implicated in parkinson's disease. We propose to use two methods to record ensemble activity in the mouse striatum, both based on our ongoing work in the rat. First, we propose to use multiple tetrode assemblies to record simultaneously from striatal neurons as mice undergo training on procedural learning tasks. Second, we propose to monitor the striatal induction of immediate-early genes (IEGs) by local cortical microstimulation and by dopamine receptor agonist treatments, and by combinations of these treatments. For each of these two methods of ensemble activity recording, we then propose to study the effects on the activity of localized striatal dopamine depletion. Based on work from our own and other laboratories, we hypothesize that such dopamine deletion will produce disruption of neuronal coding of procedural tasks by striatal neurons, and disruption of corticostriatal transmission. Finally, we propose to use these functional assays to test transgenic mice produced by members of the Center to examine the neurobiologic consequences of expressing human alpha-synuclein in the mouse (Hyman), and of deletion or mutation of the torsin A gene in transgenic mice (Breakefield). These experiments should significantly advance understanding of the neurobiology of nigrostriatal function and specific gene-based changes in this function in murine models designed to discover the pathogenesis of Parkinson's disease.

Ras proteins are key regulators of growth and differentiation, but recently have also been implicated in learning and memory functions in the brain. Rap proteins inhibit Ras signaling through the MAP kinase pathway or, via B-Raf, also can activate MAP kinase. Thus Rap and Ras proteins may have antagonistic or complementary functions in cells. Guanine nucleotide exchange factors (GEFs) can activate Rap and Ras proteins. Many Ras GEFs, but until the work described, only Rap GEF, have been identified. We have discovered new families of brain-enriched genes that code for Ras-superfamily GEFs and second messenger binding motifs. We proposed to concentrate on the calcium and diacylglycerol- regulated GEFs, CalDAG-GEFs, which are highly enriched in the striatum. We have found that CalDAG-GEFI activates Rap1, whereas CalDAG-GEFII activates Ras, as also reported by Ebinu et al., 1998. Ca2+ and DAG both augment this activation. CalDAG-GEFI and CalDAG-GEFII are both strong expressed in the projection neurons of the striatum and they co-exist in many if not most of these neurons. This co-expression may provide a mechanism by which calcium and DAG signaling can be coordinated or switched from Rap1 to Ras activation, depending on the CalDAG-GEF engaged. Ras is involved in the neuroplasticity underlying learning and memory, and we hypothesize that Rap1 may be as well. To test this broad hypothesis, we propose to examine the CalDAG-GEFs in cellular and systems-level experiments using binding assays, mutational genetic approaches, distribution and cellular localization studies, assays for CalDAG-GEFI and II coupling to glutamate and dopamine neurotransmitter systems, and tests of learning and memory and other neurologic function in transgenic and knockout mice lacking CalDAG-GEF function. The health- related significance of this work rests in the fact that the second messenger molecules for which the novel proteins have binding motifs are essential for normal brain function and for plasticity and memory. Understanding these novel second messenger signaling molecules will therefore bring insights to understanding fundamentally important brain functions and will help in elucidating brain disorders.

DESCRIPTION (Adapted from applicant's abstract): The basal ganglia have been strongly implicated in the control of saccadic eye movements on the basis of clinical and experimental studies. Oculomotor defects occur in patients with extrapyramidal disorders such as Parkinson's and Huntington's disease, and lesions or inactivation of the striatum and other basal ganglia nuclei can produce such defects experimentally. The oculomotor zone of the striatum is centered in the caudate nucleus. This nucleus projects to the substantia nigra, pars reticulata (SNr), which in turn projects to the superior colliculus. Evidence suggests that this circuit is a release circuit for saccades. The oculomotor zone has been investigated intensively with conventional single unit recording methods in highly over-trained macaques. The results of these experiments suggest that single units in the oculomotor zone of the caudate nucleus have response properties that resemble those in saccade-related regions of the frontal cortex, including the frontal eye field (FEF), the supplementary eye field (SEF) and the dorsolateral prefrontal cortex (DLPFC). These include responses in visually guided and memory-guided tasks and in sequential saccade tasks. Nothing is yet known, however, about the ensemble activity of saccade-related neurons in the oculomotor zone of the striatum (OMZ-S), or its cortico-basal ganglia loops with the FEF, SEF and DLPFC. Nor is it known how activity is modulated in the oculomotor zone and its associated cortical loops as monkeys acquire procedural learning tasks, behavior thought to be a core function of the basal ganglia. We hypothesize that during learning neurons in the oculomotor zone of the striatum will show progressively more task-related activity and that during the overtraining period population-level coding will emerge in this oculomotor zone. We further hypothesize that temporally coordinated patterns of activity will emerge in cortico-basal ganglia loops during learning and that these will be detectable using chronic multi-unit recording methods. We propose experiments based on preliminary studies to record chronically in 1-2 week bouts from initially naive macaques as they learn procedural saccade tasks. Using multiple tetrodes, stereotrodes and conventional electrodes, we Propose to study multi-unit neural activity in the oculomotor zone of the striatum during acquisition (Aim 1), to study the functional local network architecture of the oculomotor zone during performance (Aim 2), and to study activity in cortico-basal ganglia loops with simultaneous ensemble recordings in the oculomotor zone of the striatum together with the FEF, SEF and DLPFC (Aim 3). The results obtained will have significance for understanding forebrain oculomotor control circuits and for understanding oculomotor defects in extrapyramidal disorders.

DESCRIPTION (provided by applicant): The basal ganglia are centrally involved in the etiology of neurologic disorders such as Parkinson's disease and in the motor and cognitive functions that are affected in these disorders. The basal ganglia are also implicated in neuropsychiatric disorders, such as obsessive-compulsive disorder, that are closely related to and often co-morbid with anxiety disorders and depression. It is of great importance to the field of mental health to understand how the basal ganglia could contribute to such a range of brain disorders. The basal ganglia are also central to habit formation and to the neural mechanisms underlying addictive behavior. We propose a series of coordinated studies to test specific hypotheses about cognitive and action-directed functions of the basal ganglia in such habitual and repetitive behaviors. We have developed a behavioral model that allows rats to initiate voluntary movements, and to make a "decision" whether to execute one or another movement pattern in order to receive reward. Our preliminary data indicate large-scale plasticity in striatal neuronal firing patterns during procedural learning. These patterns occur as a shift occurs behaviorally from "exploration" to "exploitation" as a result of learning. We now propose to record neuronal activity in the striatum, with multi-electrode chronic recording methods, as rats perform reward-based tasks that will vary in complexity and in task parameters related to reward anticipation in order to analyze specific properties of striatal plasticity. We propose to record both spike activity and local field potential activity and to approach data analysis focusing on three specific hypotheses. Through these studies, we aim to elucidate functional properties of basal ganglia activity during learning and the plasticity of this activity during learning. Together, the proposed studies will help to clarify the function of cortico-basal ganglia loops implicated in neurologic and neuropsychiatric disorders. Understanding how patterns of activity are acquired in these brain circuits is directly relevant to understanding how abnormal patterns of activity could be laid down. Such analyses of neuroplasticity in the basal ganglia are thus relevant to work on a range of human disorders, including Parkinson's disease, Huntington's disease, Tourette syndrome and related OC- spectrum disorders. We thus believe that the proposed work is important for the mission of the NIMH, which is to understand, prevent and cure mental illness.

Parkinson's disease (PD) and Parkinson's-spectrum disorders produce both motor and cognitive impairments. We propose to examine behavioral disturbance of each type, impairmen t of procedural learning and development of L-dopa induced dyskinesias, and the striatal neural plasticity that may under lie them in rodent models of PD. We will combine multi-disciplinary methods that we and members of our Center have extensive experience with: behavioral observation using systematic rating scales, training on procedural tasks in a T-maze, chronic neuronal ensemble neuronal recording with tetrodes, analysis of immediate early gene expression, microarray gene assays and laser capture microscopy (collaboration With Project 4), and introduction of alpha-synuclein mutations (collaboration with Project 1 and extra-Center collaborations). We have carried out extensive preliminary studies and formed three functional Aims based on highly promising findings, in Aim 1, we propose to test whether plasticity in task-related neuronal activity in the dorsolateral striatum during a procedural learning in a T-maze will be abnormal in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions restricted to the area around the recording sites, in Aim 2, we propose to study the effects of alpha-synuclein overexpression on learning-related neuronal plasticity in the stdatum. We will use rats injected with viral vectors carrying mutant or normal forms of alpha-synuclein and engineered mice expressing alpha-synuclein mutations. Both of these Aims, animals will receive chronic intermittent L-dopa treatment either during or after acquisition of the learning task to test the effects of dopamine replacement therapy on learning and neuronal activity. In Aim 3, we propose to examine L-dopa induced dyskinesias in rats with 6-OHDA lesions. We will measure the activation of immediate early genes in the striosomes and in the matrix and will correlate the expression patterns with behavioral dyskinesias. We will also perform gene assays using laser-dissected striosome and matrix tissues to measure differential compartmental distributions of downstream genes in relation to dyskinesias. The results of these experiments will yield important knowledge about neural mechanisms underlying two forms of striatal plasticity implicated in parkinsonian syndromes: that related to procedural learning and that leading to the development of L-dopa induced dyskinesia in PD and related movement disorders.

[unreadable] DESCRIPTION (provided by applicant): Clinical data strongly implicate the basal ganglia, including the striatum, in the control of saccadic eye movements. For example, saccade deficits occur both in Parkinson's disease and in Huntington's disease. Experimental evidence also points to the critical role of the striatum and basal ganglia circuits in oculomotor control. The striatum has prominent saccade-related activity, and this region receives projections from oculomotor-related areas of the neocortex including the frontal eye fields, the supplementary eye fields and the caudal dorsolateral prefrontal cortex. The oculomotor zone of the striatum itself projects to the substantia nigra pars reticulata which in turn projects to, and inhibits the superior colliculus and inhibits saccades thereby. This basal ganglia pathway is used as a prime example of the release functions of the basal ganglia. We propose an experimental program to study in Maccaca mulatta the response properties of the oculomotor striatum and oculomotor cortical areas during learning and subsequent performance of a series of tasks including visually-guided sequential saccade tasks. We have developed chronic, multi-electrode recording methods for use as macaques perform a battery of saccade tasks. We will test 3 hypotheses in 3 Aims. In Aim 1, we hypothesize that many of the response properties of neurons in the oculomotor zone of the striatum and corresponding cortical regions are built up by experience. We will record during acquisition of a defined set of tasks to test this hypothesis. In Aim 2, we hypothesize that sequence-selective activity will occur in the basal ganglia as macaques perform reaching tasks. To test this hypothesis, we will train macaques on a touch screen reaching task under ocular fixation. In Aim 3, we hypothesize that spontaneously produced sequences of saccades will be represented in the brain by sequence-selective activity. We will test these hypotheses by recording from multiple electrodes implanted in the striatum and cortex as macaques perform saccade and arm reaching tasks. We aim to maximize the usefulness of the data collected for understanding oculomotor control exerted by these highly clinically important pathways in health and disease. The basal ganglia are critical for normal movements including sequential movements. Repetitive movement disorders are a hallmark of basal ganglia dysfunction. Our goal is to illuminate mechanisms disordered in these disabling human conditions. [unreadable] [unreadable]

This project focuses on the functional implications of low-frequency rhythms in the basal ganglia and neocortex. The collaborative effort involves four groups: Kopell, (Boston University), Moore (Massachusetts Institute of Technology), Graybiel (Massachusetts Institute of Technology) and Boyden (Massachusetts Institute of Technology). The project is the first collaborative research effort of the newly formed Cognitive Rhythms Collaborative (CRC), a group of Boston Area faculty members from Boston University, Massachusetts Institute of Technology, Massachusetts General Hospital Martinos Center for Biomedical Imaging, Brandeis University and Tufts University. The aims of the CRC, which fosters research and training, are to map the spatio-temporal structure of brain dynamics and connect these dynamics to brain function. This is the first project to try to understand from basic electrophysiology the growing literature suggesting that the low frequency brain rhythms are critical for both attention and learning, and that interactions among brain structures such as the basal ganglia and neocortex are central for such functions. The project makes use of the electrophysiology skills of the Graybiel lab, which is focused on the dynamics of the basal ganglia, and those of the Moore lab, focused on the neocortex, to understand the flow of information between the cortex and the basal ganglia during learning and attention. This collaboration is enriched by new molecular biology technology developed by the Boyden group. This technology, in which cells can be activated and inactivated by light, provides powerful new techniques for figuring out circuits by looking at effects of perturbations, even in behaving animals. The experimental work is guided by modeling ideas from the Kopell and Moore labs, and the output of the modeling can be tested almost immediately by the labs for quick feedback and changes. This CRC project exemplifies a new and transformational way of doing science, bridging the boundaries of disciplines and institutes to facilitate cutting edge research at the forefront of interdisciplinary endeavors.

DESCRIPTION (provided by applicant): As we repeat goal-directed behaviors, these behaviors often become habitual and so routine that we can perform them almost without thinking. This capacity to form habits is very valuable in our normal lives. When we can operate in a habitual mode, we free up cognitive resources. The process by which goal-directed behaviors become habitual has attracted great interest among basic scientists and also among physicians, because when this habit-process goes awry, behavioral problems can emerge. In neuropsychiatric disorders in which repetitive behaviors are predominant symptoms, habit forming may be in overdrive. When we lose the ready facility to form habits, thoughts and actions may lose part of the fundamental organization that normal routines confer on our behavior. The goal of the proposed work is to identify the circuit-level neural mechanisms that underlie this transition from deliberative behavioral performance to a habitual mode of performance in which the behavior continues to be performed without reference to the original goal. It is known that parts of prefrontal cortex and the striatum are necessary for habit formation, but how they act to allow the behavioral shift to habitual behavior still are not understood. We have recorded neural activity in the prefrontal cortex and striatum simultaneously through the entire process of habit formation from early acquisition to the over-training period when the habit becomes ingrained. We have found that as the shift from goal-directed to habitual behavior occurs, there are remarkable changes in the firing patterns of neurons both in different parts of the striatum and in the prefrontal cortex. We now propose experiments to determine how these regions interact and whether there are 'controller' regions by perturbing or silencing individual zones as rats form habits, in order to understand how this network of brain regions bring about shifts between flexible goal-directed behavior and less flexible habitual behavior. Disturbances in the balance between flexibility and fixity of behavior are critical in a number of neurologic and neuropsychiatric disorders ranging from Parkinson's disease to obsessive-compulsive disorder to psychosis. Thus, the experiments proposed are directly related to the mission of the NIMH to understand, prevent and cure mental illness.

DESCRIPTION (provided by applicant): The purpose of this study is for a team of chemical engineers, materials engineers and neuroscientists at MIT to develop a combined micro-cannula and deep brain electrical stimulation device for the treatment of anxiety and mood disorders. Anxiety and mood disorders are common and debilitating disorders that afflict millions of Americans. The emerging thought is that these disorders are actually rooted in disruptions in activity across neural circuits, as opposed to defects in any one region. Current treatments comprising oral and i.v. administration of therapeutics are too coarse, both spatially and temporally, to appropriately attenuate the dynamic activity across neural circuits. Our goal is to develop an implantable micro-cannula device that is capable of simultaneous infusion of multiple therapeutics, as well as electrical stimulation and real time chemical sensing. This device will be micro-fabricated in such a way as to be minimally invasive, yet durable enough to be scaled to non-human primate use. The combination of precise anatomical targeting and diverse stimulatory (electrical & chemical) capabilities should improve our ability to modulate activity across specific neural circuits with the appropriate kinetics. This proposal, and the assembled research team, combines the varied fields of micro-fabrication, materials engineering, chemistry, biology and neuroscience. Our specific goals are summarized as follows: 1) Design for failsafe delivery of neuro-modulatory therapeutics. This aim will ensure that the desired doses are delivered accurately and reproducibly. 2) Evaluate methods of improving the structural integrity and biocompatibility of the device via metal deposition and chemical functionalization. Neuro-stimulatory electrodes have been shown to lose function over prolonged periods of implantation due to gliosis. Our proposed studies will develop a method for prolonging device function by retarding gliosis. 3) Refine the peripheral components (reservoir, pump and tubing) to be a stand-alone unit suitable for chronic implantation. This will increase the utility of the proposed device, as well as represent an important step towards clinical usage. 4) Demonstrate behavior change in animal (non-human primate) models of anxiety and mood disorders by delivering stimulation (electrical & chemical) via the proposed device. 5) Demonstrate that the behavioral change is a result of modulating neural circuit activity by the proposed device. Our aim is to, demonstrate the failsafe function of the device in vivo and investigate its capability to ameliorate anxiety and mood disorder based behaviors via precise spatiotemporal control. In a final step we plan to develop feedback based activation of the device by real time sensing of pathological activity. This represents an important step towards clinical usage where anxiogenic stimuli are frequently unknown and un-predictable.

The basal ganglia lie at the critical interface between movement and motivation. The striatum, the largest structure of these deep-lying structures, is a hub for inputs from the overlying neocortex and is a main distributor of output to other parts of the brain via basal ganglia output nuclei. This system is implicated in a large range of neurological and neuropsychiatric disorders. It is modulated by neuromodulators, including by dopamine from the midbrain, deficient in Parkinson's disease. The dorsal striatum, the focus of this proposal, receives dopamine-containing input from the pars compacta of the substantia nigra (SNc). This nigrostriatal circuit degenerates in Parkinson's disease, and is a major controller of both motor behavior and responses to reinforcement and to motivational control. Our goal in the proposed research is to elucidate the physiology and anatomy of this system, focusing on critical questions related to these control mechanisms. First, our preliminary work suggests that the organization of the striatum into anatomically distinct compartments, the striosomes and surrounding matrix, is crucial in terms of behavior. Striosomes receive selective input from a restricted set of motivation/mood/emotion-related neocortical regions and are a main origin of the striatal projection to the SNc dopamine-containing neurons so important for mood and motor control. This evidence suggests special functions for striosomes, but what these functions are is not clear. Our preliminary and recent work suggests, however, that striosomes may be specialized for cost-benefit decision-making, in which costs and benefits presented in any situation have to be weighed in order for us to act. This kind of decision-making is critical for survival and, moreover, is disturbed in a number of neuropsychiatric conditions. We propose in Aim 1 to use state-of-the-art physiological and imaging methods in novel genetically engineered mice to test the hypothesis that striosomes underlie such decision-making. Second, our preliminary work has shown a remarkable anatomical organization of the striosome-SNc connection, suggesting that striosomes could exert powerful control over dopamine-containing SNc neurons. We propose to examine this system with novel combinations of optogenetic and physiological experiments combined with anatomy (Aim 2). Third, despite mounting evidence that striosome-matrix organization is a fundamentally important organizing property of the striatum, how this organization relates to the clinically critical division of the striatal output pathways into direct and indirect movement-control pathways is not understood. We aim to fill this gap by using specially engineered mice allowing direct testing of this relationship in physiological, imaging and behavioral experiments. Disturbances in the balance between cost and benefit in decision-making and movement control are critical in a number of neurologic and neuropsychiatric disorders ranging from Parkinson's disease to obsessive-compulsive disorder to psychosis. Thus, the experiments proposed are directly related to the mission of the NIMH to understand, prevent and cure mental illness.