The goal of this project is to understand the cellular pathway basis of prefrontal executive control of memory and motor information, for using past events to guide future action. Due to its strong reciprocal connections with the medial temporal entorhinal (EC) and premotor cortices (PMC), the medial prefrontal anterior cingulate cortex (ACC) is strategically positioned to serve as the interface between 'long-term memory'and 'motor planning'systems. The ACC coordinates activity-thereby gating information flow-within EC and PMC, which have distinctive anatomical circuits with unique network oscillatory dynamics. How the ACC regulates these two areas is largely unknown. While a number of neuromodulators influence cortical network dynamics, this project will focus on acetylcholine (ACh) due to its critical role in learning and memory. The overall hypothesis of this project is tht ACC projection neurons to EC and to PMC possess distinct intrinsic, synaptic, and cholinergic neuromodulatory properties that underlie differential control of their postsynaptic targets. Dr. Medalla will test this hypothesis by combining neuroanatomical tract-tracing with in vitro whole-cell patch-clamp recording and intracellular filling of retrogradely-labeled neurons in slices prepared from adult rhesus monkeys (Macaca mulatta). Structural analyses of neurons from which recordings are obtained will be conducted using high-resolution laser-scanning confocal imaging and electron microscopy of filled dendrites. This project will lead to a better understanding of prefrontal cortical microcircuitry and mechanisms underlying executive control of learning and memory systems, and the misattribution of context and drive for goal-directed action in depression and other mood and anxiety disorders. To date Dr. Medalla's research endeavors have been dedicated to understanding the structural synaptic pathway basis of functional specialization in the primate prefrontal cortex, using tract-tracing and electron microscopic techniques. The proposed project will use Dr. Medalla's experience in neuroanatomy combined with current training in electrophysiological techniques to address some outstanding issues in prefrontal circuitry, under the mentorship of Dr. Jennifer Luebke, one of the few world experts in whole-cell patch clamp in vitro slice recording techniques in primates. The project will also benefit from the support of collaborators, Dr. Alan Peters, a renowned expert in electron microscopy and cortical ultrastructure, and Dr. Douglas Rosene, an expert in primate neuroanatomy. Drs. Michael Hasselmo and Howard Eichenbaum will serve as consultants to this project;their expertise in learning and memory as well as cholinergic modulation of limbic and cortical systems will be invaluable during the implementation of these experiments. In the mentored phase, studies will focus on the intrinsic, firing and resonance properties of ACC projection neurons to EC and PMC, and their modulation by ACh. In the independent phase, studies will address the cholinergic modulation of excitatory and inhibitory synaptic responses and the structure of synapses onto these projection neurons, and the interaction EC and PMC pathways within ACC using dual patch-clamp recording and bi-directional pathway tracing. The work from the proposed studies will provide Dr. Medalla with data for high quality publications as well as preliminary data for formulating a competitive application for an R01, which will be centered on further studies of the structure and function of prefrontal cortical microcircuitry. The work in the proposed studies will be conducted at Boston University, an institution with a rich history of well-established multidisciplinary research in th field of Neuroscience. In particular, the Department of Anatomy and Neurobiology at the School of Medicine is a collaborative scientific environment with a long- standing history of seminal work on the structure and function of the primate brain. The main experiments in this proposal will be conducted in the Luebke Laboratory, located at the heart of the Medical Campus Evans Biomedical Research Center, which is fully equipped for preparation and electrophysiologic recording in acute and organotypic cortical slices and tissue cell cultures. Other aspects of the proposed experiments will be conducted in collaboration with the Rosene Laboratory for primate brain surgery and tissue processing, and the Peters Laboratory for examining tissue under the electron microscope. The confocal imaging for the proposed studies will be conducted in the Biology Imaging Core at the Life Science and Engineering Building, managed by Dr. Todd Blute, equipped with a state-of-the art Zeiss-510 laser-scanning confocal microscope. Through its extensive academic opportunities, resources, and state-of-the art facilities, BU provides an ideal environment for the mentoring and career development of Dr. Medalla, and the execution of the research goals in the proposed project. These resources at BU will facilitate the training of Dr. Medalla to become an expert electrophysiologist and initiate her own independent cutting-edge research program that investigates prefrontal pathway-specific interactions with receptors, channels, and diverse types of inhibitory neurons, using a structure-function framework at the synaptic, cellular and network levels.
The prefrontal anterior cingulate cortex (ACC) serves as an integrator of memory and motor information to enable the use of outcomes from past events to guide future action, but precisely how it does so is unclear. The focus of this study is on the cellular pathway basis of this function, using cutting-edge techniques to characterize the detailed functional and structural properties of identified ACC projection neurons directed to memory- and motor-related cortices in primates.
