Research Topics: Learning & Memory
Research Description
The research of Dr. T.W. Berger involves the complementary use of experimental and theoretical approaches to developing biologically constrained mathematical models of mammalian neural systems. The focus of the majority of currentresearch is the hippocampus, a neural system essential for learning and memory functions. The goal of this research is to address three general issues: (1) the relation between cellular/molecular processes, systems-level functions, and learned behavior; (2) the extent of which the functional dynamics of neural systems are altered by activity-dependent synaptic plasticity; (3) the extent to which the essential functions of a neural system can be incorporated within a hardware representation (e.g., VLSI circuitry).
Experimental studies involve the use of extracellular, intracellular, and whole-cell electrophysiological recording techniques, applied in vivo using anesthetized and chronically implanted animals, and in vitro using hippocampal slice preparations. A number of neurobiological issues are being investigated, including: (1) quantifying the signal processing capabilities of hippocampal neurons and the extent to which these capabilities reflect regulation due to feedforward and feedback circuitry vs. intrinsic neuronal mechanisms, such as voltage-dependent conductances or second messenger biochemical systems; (2) the spatio-temporal distribution of activity in neural networks and its dependence on input pattern and network connectivity; (3) the cellular mechanisms underlying changes in the strength of connections among neurons, i.e., synaptic plasticity, and the influence of synaptic plasticity on signal processing characteristics of neurons and the spatio-temporal distributions of activity in networks.
These and other experimental studies are used in conjunction with several different theoretical approaches to develop models of: (1) the nonlinear, input/output properties of single hippocampal neurons and circuits composed of several populations of hippocampal neurons (in collaboration with Dr. V. Marmarelis, Biomedical Engineering, USC), (2) the hierarchical relationship between synaptic and neuronal events (in collaboration with Dr. G. Chauvet, Institute for Theoretical Biology, University of Angers, France), (3) the kinetic properties of glutamatergic receptor subtypes, and (4) adaptive properties expressed by the "hippocampal-like" neural networks implemented with analog VLSI technology (in collaboration with Dr. B. Sheu, Electrical Engineering, USC).
10 Selected Publications:
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Marmarelis VZ,Zanos TP,Berger TW - Boolean modeling of neural systems with point-process inputs and outputs. Part I: theory and simulations. - Ann Biomed Eng [2009] Aug;37(8):1654-67 PubMed
Song D,Chan RH,Marmarelis VZ,Hampson RE,Deadwyler SA,Berger TW - Nonlinear modeling of neural population dynamics for hippocampal prostheses. - Neural Netw [2009] May 22;(): PubMed
Zanos TP,Hampson RE,Deadwyler SE,Berger TW,Marmarelis VZ - Boolean Modeling of Neural Systems with Point-Process Inputs and Outputs. Part II: Application to the Rat Hippocampus. - Ann Biomed Eng [2009] Jun 5;(): PubMed
Hsiao MC,Song D,Berger TW - Control theory-based regulation of hippocampal CA1 nonlinear dynamics. - Conf Proc IEEE Eng Med Biol Soc [2008] ;1():5535-5538 PubMed
Zanos TP,Hampson RE,Deadwyler SA,Berger TW,Marmarelis VZ - Functional connectivity through nonlinear modeling: An application to the rat hippocampus. - Conf Proc IEEE Eng Med Biol Soc [2008] ;1():5522-5525 PubMed
Chan RH,Song D,Berger TW - Tracking temporal evolution of nonlinear dynamics in hippocampus using time-varying volterra kernels. - Conf Proc IEEE Eng Med Biol Soc [2008] ;1():4996-4999 PubMed
Dibazar AA,Yousefi A,Berger TW - A system for move-free and real time monitoring of readiness. - Conf Proc IEEE Eng Med Biol Soc [2008] ;1():4879-4882 PubMed
Lu U,Song D,Berger TW - Nonparametric modeling of single neuron. - Conf Proc IEEE Eng Med Biol Soc [2008] ;1():2469-2472 PubMed
Song D,Hendrickson P,Marmarelis VZ,Aguayo J,He J,Loeb GE,Berger TW - Predicting EMG with generalized Volterra kernel model. - Conf Proc IEEE Eng Med Biol Soc [2008] ;1():201-204 PubMed
Bouteiller JM,Baudry M,Allam SL,Greget RJ,Bischoff S,Berger TW - Modeling glutamatergic synapses: insights into mechanisms regulating synaptic efficacy. - J Integr Neurosci [2008] Jun;7(2):185-97 PubMed
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