Edward G. Jones - US grants

somesthesis;

neurotransmitters; neurophysiology; visceral afferent nerve; neuroanatomy; axon; synapses; cell type; electron microscopy; immunochemistry; histochemistry /cytochemistry; microscopy;

visual deprivation; visual cortex;

Description: The long term objectives of this proposal are to understand the cellular and molecular mechanisms that underlie the capacity of the cerebral cortex to adapt to changes in patterns of input from the peripheral sense organs in adults. These mechanisms probably not only play a role in the fundamental processes involved in the learning of skills and the capacity to make perceptive judgements about the external world but also appear to be involved in the aberrant perceptions that accompany perturbed peripheral sensory input, for example in the case of pain of central nervous origin. The proposed studies, to be carried out in macaque monkeys, involve deprivation of sensory input from the hand and arm by peripheral nerve section or reversible conduction block, and enhanced input by electrical stimulation, the induction of acute arthritis or innocuous tactile, self-stimulation. The hand representation of the first somatosensory area of the cerebral cortex (SI) will be examined by immunocytochemical, receptor binding and in situ hybridization histochemistry to detect changes in gene expression for molecules that form the components of the gamma aminobutyric acid (GABA) and glutamate containing neuronal systems of the cortex. Changes in the representation pattern in Sl that accompany these will be mapped by multiunit recording. The effects of activity-dependent, up-or down-regulation of transmitter related molecules will be assayed by single unit/iontophoretic studies GABA and glutamate agonists and antagonists. A potential underlying basis of activity dependent plasticity, in widespread intracortical terminations of single thalamocortical axons, will be examined in correlative neuroanatomical tracing studies.

The long term objective of this project is to analyze the sequence of changes that lead to the maturation of the neurotransmitter systems of the cerebral cortex during a critical period of postnatal development when the cortex is subject to systemic and peripheral activity-dependent plasticity. Such plasticity appears to depend in large part on the development of normal neurotransmitter function in the cortex. At every stage of this, there are windows of vulnerability during which perturbations can have long lasting consequences. The immediate aims of the project are focused on the somatosensory cortex of mice and on the inhibitory neurotransmitter, GABA and the excitatory neurotransmitter, glutamate. A combination of electron microscopy, immunocytochemistry, axonal transport, receptor autoradiography and in situ hybridization histochemistry will be used in normal animals and in animals subjected to perturbations of facial vibrissae in the critical period to chart changes in synapse distribution and gene expression over time.

This project is focused on the cellular pathology of the schizophrenic brain. The fundamental hypothesis to be explored is that disturbances of neuronal migration and/or preprogrammed cell death in the second trimester of pregnancy will compromise the associative circuitry interconnecting prefrontal and medial temporal cortex and mediodorsal (MD) thalamus. We have observed that interstitial neurons of white matter beneath the prefrontal and temporal cortex are maldistributed in schizophrenia which is compatible with the suggestion that their normal migration to the cortex or their developmentally-regulated death cycle could have been disrupted in the second trimester of pregnancy. A disturbance in cell settling patterns in the cortex could cause a disruption of intrinsic cortical connectivity which is compatible with hypofrontality in schizophrenia and could result in secondary effects in MD and in medial temporal cortex. Neuronal pathology has been reported in both of these brain regions in schizophrenia. This pathology could result in a functional disconnection in the proposed "psychosis" circuitry, a concomitant of which is down regulation of gene expression for transmitter and receptor related molecules. A unique collection of schizophrenic and control brains has been evaluated clinically, collected, matched for age, sex and autolysis time and prepared for analysis by a novel method developed in the last grant period. Anatomical, histochemical, immunohistochemical and in situ hybridization methods will be applied to the targeted brain areas to detect changes in specific cell populations, in components of the inhibitory and excitatory cortical and thalamic circuitry, and in features indicative of disordered neuronal migration or programmed cell death. Specific research aims include: quantify specific neuronal populations in the medial temporal and prefrontal cortex and MD, evaluate the relative densities of immunocytochemically defined afferent fiber systems in the cortex and MD, quantify potential changes in gene expression for transmitter and receptor related molecules, quantify and assess morphology; continue to make prospective clinical evaluations and collect brains of schizophrenic and control subjects.

The long term objectives of this proposal are to understand the cellular and molecular mechanisms that underlie the capacity of the cerebral cortex to adapt to changes in patterns of input from the peripheral sense organs in adults. These mechanisms probably not only play a role in the fundamental processes involved in the learning of skills and the Capacity to make perceptive judgements about the external world but also appear to be involved in the aberrant perceptions that accompany perturbed peripheral sensory input, and in adaptation to central and peripheral nervous injury. The proposed studies, to be carried out in macaque monkeys, involve three principal sets of. experiments. The first set deals with how converging and diverging connections extending from the -thalamus to the somatosensory cortex may facilitate plasticity of representations of the body, but -place constraints upon the extent to which changes can occur. The second set of experiments deals with the issue of whether pre-existing connections within the somatosensory cortex itself are sufficient to permit large scale changes in representational maps after long-term deafferentation or whether it is necessary for new connections to be formed. This set introduces a new model for the studies of cortical plasticity, the face representation, and addresses the issue of whether it is protected" from other parts of the somatosensory cortex by an absence of interconnections. The third set of experiments deals with the normal patterns of gene expression for receptor subunits and other polypeptides that form components of the inhibitory (GABAergic) and excitatory (glutamergic) transmitter systems of the cerebral cortex and thalamus and asks to what extent activity-dependent changes in gene expression for these molecules accompany and/or contribute to representational plasticity. The methods are a combination of anatomical tracing, physiological mapping in normal animals and in animals in which part of the thalamic representation has been selectively lesioned, coupled with immunocytochemistry and in situ hybridization histochemistry, and including a search for novel GABA-A receptor subunit genes.

DESCRIPTION (Verbatim from the Applicant's Abstract): This research is devoted to the development of the corticothalamic system joining the somatosensory area of the cerebral cortex to the ventral posterior nucleus of the thalamus. Corticothalamic fibers far outnumber those of the thalamo-cortical projection, and provide the main pathway for integrating the activities of the cerebral cortex and thalamus in relation to the state of consciousness. However, their developmental history and especially their potential role in organizing the development of the body-specific representation in the thalamocortical projection during the perinatal period has not been examined. The research proposed will examine the growth of individual corticothalamic fibers as they establish their patterns of distribution in the thalamus, during the period when the cortex is itself being innervated by the thalamus. The principle experimental model is a mouse in vitro preparation. Labeling of populations of growing axons will be carried out to establish temporal patterns of innervation and labeling of single axons and their parent cells by intracellular injections of dyes will establish the morphogenetic sequence of cell-type specific projections. The influence of specific growth factors on corticothalamic cell and axon growth will be examined. Physiological methods involving whole cell recording, in vitro, will measure the maturation of corticothalamic function and its interactions with sensory inputs from the skin via various forms of receptors. The synapses and their associated receptors will be identified and quantified using electron microscopic immunocytochemistry. The overall hypothesis is that interactions between corticothalamic fibers and thalamic cells are critical in establishing the fine grain topography that characterizes thalamocortical innervation. This forms a substrate for interactions between thalamus and cortex that underlie changes in conscious state in maturity. It is proposed that developmentally regulated changes in synaptic distribution and the receptors engaged are critical to the normal maturation of these interactions. Defective maturation may be a concomitant of or a basis for certain forms of seizures in young individuals.

mental disorders; nervous system; genome; Mammalia;

The long term objectives of this proposal are to understand the cellular mechanisms that underlie the capacity of the cerebral cortex to adapt to changes in patterns of input from the peripheral sense organs in adults. These mechanisms not only underlie the capacity of the cortex to make perceptive judgments about the external world but appear also to be fundamentally involved in the learning of skills and in relearning them after stroke and other forms of brain injury, as well as in the aberrant perceptions that accompany central and peripheral lesions of sensory pathways. The proposed studies to be carried out in adult macaque monkeys, involve four sets of experiments. All deal with the role of activity dependent changes in cells and their axonal distribution patterns at subcortical and cortical levels of the somatosensory pathways in influencing the representation of the body surface in the somatosensory cortex and seek to determine the relative contributions of these changes to representational plasticity occurring after lesions of peripheral nerves or of spinal cord pathways. The first set of experiments deals with the issue of whether central and peripheral forms of deafferentation result in the same or in fundamentally different transsynaptic changes in the brainstem and thalamus. The second set of experiments deals with the extent to which the two forms of deafferentation lead to withdrawal from the thalamus and from the cerebral cortex of axon terminations of cells subjected to transsynaptic changes, as a mechanism promoting expansion of representations with intact peripheral innervation. The third set of experiments deals with the influence of the two forms of deafferentation on two fundamentally different sets of cells in the thalamus that appear to be engaged in different aspects of thalamocortical integration. The fourth set of experiments deals with the capacity of central and peripheral forms of deafferentation to evoke increased gene expression of growth factors and their receptors, and with the possibility that withdrawal of axons of deprived cells may be accompanied with sprouting of axon terminations of cells with intact innervation in the thalamus and cerebral cortex. The methods to be used are a combination of physiological localization and anatomical tracing of the axons of individual nerve cells, coupled with immunocytochemistry to define cells populations and in situ hybridization histochemistry to define levels of mRNA expression.

neural plasticity; sensory cortex; Primates; animal colony; clinical research;

[unreadable] DESCRIPTION (provided by applicant): This is a revised application for a jointly sponsored Ruth L. Kirchstein Institutional Predoctoral Training Program grant from 40 neuroscientists across 11 academic departments at the University of California, Davis. The goal of the program is to provide a broad training in the fundamental principles of neuroscience for entering students that will lay solid foundations for their specialized research in advanced years and provide them with the broad perspective essential for their establishing successful independent research programs in neuroscience in their future careers. The program will operate under the auspices of the existing interdepartmental graduate program in neuroscience at UC Davis which offers the scope and flexibility needed to meet our training objectives. [unreadable] The Training Program requests support for 6 predoctoral trainees to be selected annually by an Advisory Committee. Trainees will receive one year of support from the grant, typically in their first year. Internal support mechanisms and other extramural grants, that will be meshed with this program, will be used for support of the remaining -3-4 years of advanced training. Trainees will participate in a teaching program especially designed to give exposure to as broad a range of modern neuroscience subdisciplines and technologies as possible including cellular and molecular neuroscinece, neuroanatomy and neurophysiology, neurogenetics, systems neuroscience, cognitive neuroscience, computational neuronscience and modeling, the neurobiology of disease, and central neural mechanisms of behavior. [unreadable] Trainees will receive a rigorous basic training through formal course work, seminars and laboratory rotations and will participate in colloquia in which they will be expected regularly to make oral presentations. Students will thus be well-prepared for their dissertation research and for future, independent careers in basic and disease-related neuroscience research. [unreadable] [unreadable] [unreadable]

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Knowledge of cerebral cortical connectivity in primates is essential for understanding higher brain mechanisms of sensation, perception and cognition and their disorders but connection tracing studies are increasingly uncommon, older studies are accessible only through publications which represent an earlier investigator's interpretation of the data, and access to the original data for re-interpretation is commonly unavailable. Retrieval of archives of experimental material and conversion to an accessible digital form presents considerable logistical and other handicaps. We seek to develop a comprehensive and ongoing archive of material demonstrating cortical and subcortical connectivity in rhesus monkey brains, in which all the histological material from individual experiments is available in its digital form, with a suitable search engine providing open access to all investigators. In this way, original experimental data can be annotated and re-interpreted as newer parcellations of cortical and subcortical structures are made on the basis of accumulating functional and clinical data. The current proposal builds on expertise in constructing high resolution microscopic atlases of primate brain architecture and will create a searchable database of connections of the cerebral cortex in the adult rhesus monkey. A pipeline will be established in which targeted cortical areas in a series of monkeys will be injected with a tracer transported both retrogradely and anterogradely. Digital data about each individual brain will be collected by means of: structural mri;serial imaging of the sectioned blockface as each 40[unreadable]m section is removed during sectioning of the brain;imaging at high resolution of alternate sections through the brain stained for the transported tracer or stained with the nissl stain;warping images of the sections back onto the blockface images of the brain and mris to provide a 3d volumetric dataset for each brain. The searchable database into which the individual datasets will be stored will incorporate a capacity to annotate the dataset from each experimental brain in relation to a standard high resolution digital atlas of the rhesus monkey brain, a capacity for making queries about connections by name or by visual inspection of injected regions or of likely sources of afferents and targets of efferents, a capacity for interoperability with databases of other relevant neuroscience information. The database will also permit incorporation of datasets of connectivity drawn from material in publications and/or existing slide. The result will be a living archive to which data essential for the understanding of the pathophysiology of neurological and neuropsychiatric disorders can continue to be added and queried.