John H. Freeman - US grants

DESCRIPTION (provided by applicant): The proposed research project is the continuation of an analysis of developmental changes in the central nervous systems that underlie the ontogeny of eyeblink classical conditioning in rats. The cerebellum and its synaptic connections with the pontine nuclei and inferior olive are essential components of the eyeblink conditioning neural circuitry. The mossy fiber projection from the pontine nuclei to the cerebellum forms the input pathway for the conditioned stimulus (CS) and the climbing fiber pathway from the inferior olive to the cerebellum forms the unconditioned stimulus (US) pathway. The initial findings of this project demonstrate that the ontogeny of eyeblink conditioning is correlated with developmental changes in stimulus-elicited and learning-related neuronal activity in the cerebellum. The input pathways to the cerebellum also undergo significant developmental changes. One of the most striking developmental changes in the input pathways is the development of neural feedback from the cerebellum to the inferior olive. Cerebellar feedback regulates the input pathways and thereby regulates the induction of learning-specific plasticity in the cerebellum. The initial studies suggest that the ontogeny of eyeblink conditioning is due to the development of interactions between the cerebellum, pontine nuclei, and inferior olive. The findings of the initial experiments of this project are promising, but additional studies are required to determine the origins and mechanisms of the aforementioned developmental changes in the cerebellum and its interactions with brainstem nuclei. The first specific aim of the proposed project will examine the anatomical development of the CS and US pathways. The second specific aim will examine the physiological mechanisms underlying the developmental changes in the CS pathway using electrical stimulation of the pontine nuclei, reversible inactivation of the cerebellum and red nucleus, and behavioral methods. The third specific aim will examine the mechanisms underlying the development of the US pathway using electrical stimulation of the inferior olive, pharmacological manipulations of the inferior olive, and behavioral methods. The fourth specific aim will examine developmental changes in the induction of neural plasticity within the cerebellum using in vivo and in vitro neurophysiological techniques. Elucidating the neural mechanisms underlying the ontogeny of eyeblink conditioning may lead to the discovery of general principles concerning the relationship between neural and behavioral development. In addition to the basic research goals of this project, the results of the proposed studies may lead to a better understanding of the functional pathology associated with various developmental disorders that affect the nervous system including fetal alcohol syndrome, exposure to environmental neurotoxins, infantile autism, and Down's syndrome.

[unreadable] DESCRIPTION (provided by applicant): Inhibitory conditioning is a central component of theoretical models of associative learning but its neural basis has not been fully elucidated. Conditioned inhibition is generally thought to be due to the development of an association between a conditioned stimulus (CS) and the omission of an unconditioned stimulus (US). The proposed project will initiate a research program to examine the neural mechanisms of inhibitory classical conditioning. The eyeblink conditioning preparation will be used in these experiments in order to compare the neural mechanisms of inhibitory conditioning with the previously identified neural mechanisms of excitatory conditioning. The experiments of Specific Aim 1 will investigate the role of the cerebellar cortex in conditioned inhibition using excitotoxic lesions, unit recording, and reversible inactivation. In the experiments of Specific Aim 2, pharmacological inactivation will be used to assess the roles of several possible sites within the neural circuitry underlying the acquisition and expression of excitatory eyeblink conditioning in the acquisition of conditioned inhibition. The experiments of Specific Aim 3 will determine whether conditioned inhibition involves neural systems that are distinct from the neural systems that mediate excitatory conditioning. The fundamental importance of inhibitory learning underscores the need to study its neural mechanisms. The proposed research project will provide important initial steps toward determining the neural mechanisms of inhibitory classical conditioning. A successful analysis of the neural mechanisms of inhibitory classical conditioning may lead to the application of this experimental approach to the study of excitatory and inhibitory processes that occur in other learning situations. The results of these studies may also lead to a better understanding of the functional pathology associated with various psychiatric disorders that involve deficits in behavioral inhibition.

DESCRIPTION (provided by applicant): The cerebellum and its connections with other parts of the brain act as functional loops that underlie various aspects of motor control, learning, attention, language, working memory, and emotion. Disruption of these functional loops may be the basis for symptoms of schizophrenia, bipolar disorder, autism, fragile X syndrome, and other disorders. The current proposal is designed to examine sensory inputs to the cerebellum that are necessary for learning and to determine whether the cerebellum sends feedback to these sensory inputs during learning. Pavlovian eyeblink conditioning will be used as the method for assessing cerebellar learning. Previous findings from this project identified the neural pathway necessary for auditory eyeblink conditioning, which includes the medial auditory thalamus (MAT) and its projections to the pontine nuclei. MAT neurons exhibit learning-related changes in activity during eyeblink conditioning that are hypothesized to be driven by feedback from the cerebellum. The first aim of the current proposal is to identify the neural pathway(s) necessary for visual eyeblink conditioning and to determine whether the visual thalamus also shows learning-related activity using reversible inactivation and high-density neuronal recording methods. Aim 2 is to determine whether learning-related activity in the thalamus is driven by the cerebellum or its downstream target nuclei by recording neuronal activity in the thalamus while inactivating the cerebellum and its target nuclei. Aim 3 will investigate the mechanisms underlying cross-modal facilitation of cerebellar learning using high- density neuronal recording methods. Aim 4 is to determine the roles of auditory and visual areas of the cerebral cortex in cerebellar learning using reversible inactivation. The proposed project will significantly increase knowledge about the nature of cerebellar interactions with sensory areas of the brain that underlie associative learning. Findings from this project could be used to develop methods for treating various symptoms caused by pathology in cerebellar interactions with other brain areas.

DESCRIPTION (provided by applicant): The proposed project is designed to examine the neural mechanisms underlying the ontogeny of cerebellar learning using short delay and trace eyeblink conditioning procedures. Previous findings from this projected showed that the ontogeny of delay eyeblink conditioning is highly correlated with developmental changes in the induction of neuronal plasticity within the cerebellum. A substantial body of evidence now indicates that the development of auditory input to the pontine nuclei plays a critical role in the ontogeny of cerebellar learning. The current proposal significantly extends these findings to elucidate the nature of developmental changes in auditory input to the pontine nuclei in Aim 1. It will also test the more general hypothesis that cerebellar learning depends on the development of sensory input to the pontine nuclei, not on the development of cerebellar plasticity mechanisms in Aim 2. That is, the cerebellum is capable of learning early in development but only with early developing sensory systems (olfactory, gustatory, and somatosensory), whereas cerebellar learning emerges later when late developing sensory systems (auditory and visual) are used. The scope of the project will be extended to examine the development of mechanisms underlying trace eyeblink conditioning, a cerebellar learning paradigm that requires the hippocampus and cortical projections to the pontine nuclei (Aim 3). New methods for recording neuronal activity in rat pups with moveable tetrodes will be used to examine the development of thalamic, pontine, and hippocampal activity during eyeblink conditioning. Nothing is known currently about the ontogeny of learning -related activity in the thalamus or hippocampus. Thus, the findings of these experiments will be novel and significant.

? DESCRIPTION (provided by applicant): Memory deficits are found with many neurological disorders and the breakdown of interactions between memory systems can be particularly debilitating. Different memory systems typically combine and interact to influence everyday behavior. The amygdala and cerebellum have traditionally been viewed as essential players in different types of memory, emotional and motor memory, respectively. These memory systems have been viewed as largely independent. However, recent evidence suggests that the amygdala facilitates cerebellar learning. Our preliminary data indicate that reversible inactivatio of the amygdala in rats severely impairs acquisition and retention of eyeblink conditioning, a type of cerebellar learning. Moreover, amygdala inactivation reversibly impairs the development of learning-related neuronal activity in the cerebellum. This proposal is designed to elucidate the mechanisms underlying interactions between the amygdala and cerebellum. Aim 1 is to determine how the amygdala influences cerebellar function during eyeblink conditioning using reversible inactivation of the amygdala and multi-electrode neuronal recording in the cerebellum. Aim 2 is to determine whether or not the amygdala interacts with the cerebellum through the conditioned stimulus input pathway to the cerebellum using reversible inactivation of the amygdala, axonal tracing, electrical brain stimulation, and multi-electrode neuronal recording. Aim 3 is to determine whether or not amygdala memory consolidation is necessary for facilitating cerebellar learning using protein synthesis inhibition and NMDA receptor blockade in the amygdala and multi-electrode neuronal recording in the pontine nucleus. This project would provide an unprecedented analysis of amygdala-cerebellum interactions.

Learning is how organisms adapt to changes in their environment and involves the coordination of neural systems mediating cognition, emotion, and motor control. The major goal of the proposed research program is to elucidate the neural circuit mechanisms underlying interactions between cognitive, emotional, and motor systems during associative learning. Interactions between these neural systems are particularly important because the context and emotional significance of stimuli provide essential information for acquisition and performance of motor responses. The breakdown of interactions between cognitive, emotional, and motor systems in various neurological disorders can therefore have devastating consequences for learned behaviors. The prefrontal cortex, amygdala, and cerebellum play significant roles in cognition, emotional responses, and motor learning, respectively. The proposed research program constitutes a comprehensive analysis of cerebellar interactions with the amygdala and prefrontal cortex during associative motor learning. Our general conceptual framework is that the cerebellum receives inputs from the amygdala and prefrontal cortex via the pons regarding which stimuli are important and when they occur, and the cerebellum then sends error-driven feedback to these forebrain systems to facilitate learning about important events. This conceptual framework takes into account the bidirectional relationship between the cerebellum and the relevant forebrain systems as well as interactions between forebrain systems. Multi-site electrophysiology, pathway-specific optogenetics, and precise behavioral analyses will be combined to investigate circuit-level interactions between the cerebellum, amygdala, and prefrontal cortex during associative learning and extinction (inhibitory learning) training. The proposed studies would significantly advance understanding of the neural circuit mechanisms underlying cerebellar interactions with the forebrain. This would be a substantial contribution to the field because it has been known that the cerebellum must interact with the forebrain in many contexts that are crucial for everyday life such as learning, memory, planning, control of emotions, and communication, but very little is known mechanistically about how the cerebellum interacts with the amygdala and prefrontal cortex.