Julie Fudge - US grants

DESCRIPTION: (Applicant's abstract) The ventral ('limbic-related) striatum mediates motivated behavior, and is considered an important anatomic Substrate of psychosis. The amygdala, a prominent limbic structure, links complex sensory stimuli to their emotional significance. One way the ventral striatum can be defined is based on inputs from structuresthat mediate emotional processing the amygdala; orbitomedial prefrontal regions linked to the amygdala, and the dorsal tier dopamine (DA) neurons. The ventral striatal 'shell' is a unique subregion that receives restricted inputs from these structures, and is charactenzed by 1. Relatively low calbindin-Dk28 (CaBP) staining, 2. Multiple cellular ('interface') islands with differential distributions of substance F, enkephalin, acetyicholinesterase (AchE), tyrosine hydroxylase (TH), and D1 mRNA, 3. Regions of precise overlap between amygdaloid afferents and cell clusters associated with specific transmitters, 4. Regions of tight overlap between amygdaloid and cortical afferents. We hypothesize that the caudoventral striatum and adjacent amygdalostriatal area (Astr) is a special part of the ventral 'limbic' striatum that is devoted to temporal lobe inputs, based on similar criteria. The temporal lobes mediate auditory and visual processing, are interconnected with the amygdala, and are a site of abnormalities in schizophrenia. Our preliminary data suggest that, like the ventral striatum, the caudoventral striatum/Astr area: 1. Receives afferents from brain structures mediating emotion: amygdala, specific regions of cortex linked to the amygdala, and the DA neurons. 2. Receives input from a caudal component of the 'dorsal tier' of DA neurons 3. Has a CaBP-poor region, and multiple cellular islands associated with varying distributions of substance F, enkephalin, AchE, TH, and D1 mRNA, similar to that found in the shell. The first goal of these studies is to determine whether the caudoventral striatum/Astr area is part of the ventral striatum based on connectional, cytoarchitectural, and histochemical features. Our second aim is to examine the hypothesis that the amygdala projects to cellular clusters containing substance P and Dl receptor mRNA in the caudoventral striatal/Astr area, and is therfore in a position to activate these transmitter/receptor specific pathways. Our third aim is to determine whether amygdaloid and temporal cortical inputs converge in the caudoventral striatum/Astr area. The results of these studies will provide an anatomic framework for understanding how emotionally significant auditory and visual information is processed in the striatum.

DESCRIPTION (provided by applicant): Structural abnormalities of the amygdala/hippocampal complex are a consistent finding in schizophrenia. In animal models, neonatal damage to the amygdala/hippocampal complex results in adult onset dopamine (DA) dysregulation, another key feature of this illness. Maintaining the integrity of amygdala/hippocampal circuits therefore appears critical to later DA function. We have previously shown that the extended amygdala, a major output region of the amygala and other temporal lobe structures, has broad inputs to the dopamine neurons. This pathway is thus a potential route by which amygdala-hippocampal abnormalities may eventually lead to DA dysregulation. The proposed studies will examine how the amygdala and hippocampus can influence the midbrain DA system through the extended amygdala. The fact that temporal lobe injury results in DA dysregulation only later in development suggests that plastic changes eventually influence DA output. Our preliminary results show that B lymphocyte 2 protein (bcl-2), which protects cells from excitotoxic damage and also has neurotrophic effects, is highly concentrated in specific subregions of the adult primate temporal lobe. Our preliminary results show high concentrations of Bcl-2 positive cells in the extended amygdala, and in subregions of the amygdala and hippocampus associated with schizophrenia. The presence of bcl-2 in specific circuits may help to identify excitatory pathways most susceptible to plastic changes and/or excitotoxic stress in adult animals. The proposed studies will identify temporal lobe circuits that influence DA through the extended amygdala. Specifically we will: 1) identify direct amygdaloid and hippocampal inputs to the extended amygdala-DA pathway, 2) identify indirect hippocampal pathways through the amygdala that influence the extended amygdala, 3) determine whether specific amygdaloid and hippocampal input/output paths contain Bcl-2 immunoreactive cells, 4) determine the extent to which hippocampal inputs overlap amygdala subregions that project to the extended amygdala, and the extent to which this input overlaps inhibitory interneurons and bcl-2-containing cells.

DESCRIPTION (provided by applicant): Symptoms of many psychiatric disorders are exacerbated by stressful life events. The amygdala, which signals the presence of emotionally aversive stimuli and is dysregulated in many psychiatric disorders, has massive outputs to two key nodes of the 'stress circuit': the bed nucleus of the stria terminalis (BNST) and the central amygdaloid nucleus (CeN). Our previous work shows that the BNST and CeN have direct access to the midbrain dopamine system, which is also dysregulated by repeated stress. In this proposal we will use a monkey model to 1) examine the scope and organization of afferent inputs to specific subdivisions of the BNST and CeN, and 2) determine how information channeled through these two key nodes of the stress circuit are positioned to afferently regulate specific DA neurons and their output paths. Heightened stress reactivity is proposed to be a major risk factor for a broad range of mental illnesses, yet little is known of the organization of stress circuitry in primate models. The BNST and CeN form the rostral and caudal poles, respectively, of the central 'extended amygdala', which has been conceptualized as a unified macrostructure involved in responses to stressful stimuli. In rats, specific subdivisions of the BNST and CeN have differential responses to chronic stress, antidepressants, alcohol, and to drugs of abuse, suggesting subdivision-specific input/output paths. Despite the apparent 'symmetrical'organization of the BNST and CeN, dissociations in BNST and CeN responses to various types of stimuli suggest fundamental connectional differences. Our preliminary data in nonhuman primate indicate that while some brain regions send inputs to both BNST and CeN, other afferent systems selectively target only the BNST. This organization suggests that the BNST and CeN play related but separate roles in stress responses, and that there are fundamental differences from the rat model. The DA system is activated by novel and stressful stimuli. Since even mild stress has a significant impact on DA efflux in mesolimbic and mesocortical targets, connections between the BNST and CeN is one direct way aversive stimuli can afferently regulate this system. Our previous studies show that the DA neurons receive input from the BNST and CeN. Here, we propose to 1) more directly examine whether there is a differential afferent influence of the amygdala, hippocampus, and cortex on the BNST and CeN (Aims 1 and 2), and 2) examine how open loop systems from specific amygdaloid nuclei are channeled through BNST and/or CeN subregions to target specific DA neuron/output paths in the same animal (Aim 3). PUBLIC HEALTH RELEVANCE: Stressful life events are channeled through brain regions that regulate motivated behaviors through transmitters such as dopamine. We will examine how brain regions involved in cognition influence stress circuits, as well as specific ways that stress-related information can influence motivated behavior through the dopamine system.

DESCRIPTION (provided by applicant): Integrating social networks through amygdalostriatal paths A longstanding focus of our laboratory is the identification of pathways through the primate amygdala that are positioned to mediate symptomatology of severe mental illnesses. Because emotional dysregulation in psychiatric syndromes is often expressed as maladaptive social function, the proposed studies examine how networks involved in social function interact with 'salience detection' pathways in the amygdala and striatum of the nonhuman primate. Tract tracing studies in nonhuman primate enable more accurate interpretation of neuroimaging results in humans, and are a critical bridge for understanding details of primate brain structure on a cellular level. In this set of studies, we examine two cortical networks that are frequently dysregulated in psychiatric illnesses: the 'salience detection' network (areas 25/32, agranular insula) which monitors internal physiologic states to 'mark' salient cues, and the 'social monitoring' network (areas 24/14/dysgranular cortex), which detects and interprets the meaning and value of others' actions. These networks are often considered physiologically distinct. However, since emotional dysregulation in human illness is frequently expressed in misinterpretation of social cues, integration of 'salience' and 'social monitoring' networks must exist. We propose that specific circuits through the amygdala and striatum are substrates for this integration. Aim 1 will map the boundaries of inputs from 'social-monitoring-associated' cortex in the amygdala, and the resulting organization of outputs to the striatum. In Aim 2, we will place retrograde tracers into novel striatal sectors targeted by 'social' corticoamygdala-striatal path in Aim 1 to determine whether they are defined by direct cortical projections from the social monitoring network. In Aim 3 we will examine the amygdala under higher power, to determine whether converging inputs terminals from nodes of the 'salience' and 'social monitoring' networks predominantly synapse on the same neural population, or on separate subpopulations.

PROJECT SUMMARY Emotional dysregulation and altered dopamine (DA) function occur in many psychiatric disorders. A central goal of our research program has been to understand how the amygdala, a key regulator of emotion, afferently influences DA function at the cellular level in primates. In the previous funding period, we found that amygdala-central extended amygdala (CEA) paths target DA subpopulations that lie mainly outside the ?classic ventral tegmental area (VTA)?, with downstream effects on ?limbic-associative? striatum. The CEA mediates various stress-induced behaviors, and has a high content of neuropeptides, including corticotropin releasing factor (CRF). Stress-induced activation of the CEA and/or manipulation of CRF in the CEA, has downstream effects on DA cells, and precipitates lasting changes in goal-directed responses such as drug seeking, social responses, and compulsive behavior. Very little work has been done on understanding this model in higher primates, in part because of lack of a detailed circuit map at the ?meso- anatomic? level. In mapping the CEA-DA-striatal path in nonhuman primates we found that the CEA has a strong input to parabrachial pigmented nucleus (PBP) and A8 neurons (i.e. DA subgroups outside midline (?classic?) VTA). While usually not a subject of research, these DA neuronal groups are disproportionately expanded in human and nonhuman primates. We also found that 1) the CEA projection is subdivision-specific, 2) CRF is highly expressed in CEA-DA afferent inputs, and, 3) CEA-DA afferent paths are associated with specific efferent paths to striatal regions outside the ?classic? nucleus accumbens. Thus, a CRF-enriched CEA- DA circuit projects largely outside the ?classic (medial) VTA? (mesolimbic) path, to modulate central/caudal ventromedial (?limbic-associative?) striatum. In this proposal, we will examine the on CEA-DA-striatal circuit at a more ?high resolution? level to understand cell-type specific connections to and from the key DA neuronal populations that are involved in the nonhuman primate: the PBP and A8 subgroups. After quanitifying CRF contacts (from all sources) on DA versus non-DA cells (AIM 1a), we will examine 1) the extent to which glutamate, GABA, or both exist in the CEA-DA path, and their co-expression with CRF (AIM 1b), 2) the extent to which the CEA targets DA neurons, non-DA neurons, or both (AIM 2), 3) whether striatal-projecting neurons in the PBP and A8 receive direct CEA contacts (AIM 3).

In primates, the amygdala has a central role in learning and responding appropriately to social behaviors. Difficulty in social function is a feature of many psychiatric disorders, and early social difficulties may be a harbinger of disease onset. In both humans and monkeys, the amygdala matures in parallel with evolving social repertoires during a protracted period from infancy through young adulthood. Surprisingly, almost nothing is known of cellular changes underlying amygdala growth, or correlates with developing social behaviors. This proposal focuses on a unique group of immature neurons found in the postnatal primate amygdala (including human), and their potential for shaping social behavior over development. Importantly, these immature neurons do not exist in rodents. Along with several other groups, we have characterized immature neurons in the primate amygdala, and recently found that they are poised to mature to glutamatergic projection neurons. This finding is buttressed by recent post-mortem human data showing that mature neurons are added to specific amygdala nuclei in neurotypical children. We hypothesize that the path from immature to mature neurons in specific amygdala regions is interrupted by early life stress, and correlates with the development of atypical social behavioral outcomes. Early life adversity in the form of maternal deprivation potently alters social behavior and amygdala function in children and monkeys. We hypothesized that maternal deprivation would alter immature neuron growth trajectories, and recently used microarray analyses to specifically explore the immature neuron cells. We found strong, specific downregulation of genes governing neuroblast differentiation and migration in deprived infants, suggesting maturational disruption by early life events. We also found a correlation between the most strongly affected gene transcript (tbr1), and time spent in typical social behavior across all animals. To begin interpreting these genetic changes, we began to investigate cellular data from the same cohort (fixed hemisphere). Preliminary data suggest a reduced ratio of mature: immature neurons in maternally deprived infants, raising the possibility of slowed or reduced growth of immature neurons. In this proposal, we use archived tissue from two cohorts (infant and adolescent) to more fully explore: 1) cellular changes in immature neurons during transition from infancy to adolescence, 2) how early life stress impacts this trajectory, and 3) associated behavioral consequences. Aim 1: What is the normal trajectory of change in mature-to-immature neuron ratios between infancy and adolescence in normal control nonhuman primates? What cellular features (e.g. cell size, dendritic arborization, protein expression) track this? Does maternal deprivation alter this trajectory? Aim 2: Across all animals in each cohort (infant and adolescent), what neural maturation measures track duration (time spent) in typical social behaviors? Which behavioral developmental trajectories in each cohort are most correlated with typical neural maturation? With atypical neural maturation?