Douglas A. Baxter, Ph.D.
- Adjunct Faculty, Professor, Research, Neurobiology & Anatomy
Cellular And Network Processes Underlying Behavior And Behavioral Plasticity
A set of fundamental issues in neuroscience concerns the neural mechanisms underlying behavior and behavioral plasticity (e.g., learning). It is generally believed that the ability of the nervous system to generate behaviors arises from the organization of neurons into circuits and that the functional capabilities of these circuits emerge from the interactions among the intrinsic biophysical properties of individual neurons, the pattern of synaptic connections among these neurons and the physiological properties of the synaptic connections. To adapt to an ever changing environment, the performance of these neural circuits must be modified, either by feedback occurring during the behavior or by previous experience.
Our laboratory uses two approaches, one computational and the other experimental, to investigate how neural circuits are organized, what principles underlie their function, and the consequences of sensory inputs and of modulatory influences.
Empirical studies utilize the marine mollusc Aplysia, which has a relatively simple nervous system with large, identifiable neurons that are accessible for detailed anatomical, biophysical and biochemical analyses. Computational studies utilize a program entitled “Simulator for Neural Networks and Action Potentials (SNNAP)”, which is a general-purpose tool for the rapid development and simulation of realistic models of neurons and neural networks. Currently, we are examining two neural circuits, one mediating a defensive withdrawal reflex and another mediating feeding behaviors. Such analyses of relatively simple neural circuits can contribute substantially to an understanding of basic principles that underlie functions of more complex neural systems.
Neural circuit mediating the tail/siphon withdrawal reflex. B: Intracellular recordings of an action potential in a sensory neuron (SN) and the resulting excitatory postsynaptic potential in PI-4. C: Computer simulation of the synaptic connection between SN and PI-4.
- Smolen, P., Baxter, D.A. and Byrne, J.H. A model of the roles of essential kinases in the induction and expression of late long-term potentiation. Biophys. J., 90: 2760-2775, 2006.
- Lorenzetti, F.D., Mozzachiodi, R., Baxter, D.A. and Byrne, J.H. Classical and operant conditioning differentially modify the intrinsic properties of an identified neuron. Nat. Neurosci., 9: 17-19, 2006.
- Song, H., Smolen, P., Av-Ron, E., Baxter, D.A. and Byrne, J.H. Bifurcation and singularity analysis of a molecular network for the induction of long-term memory. Biophys. J., 90: 2309-2325, 2006.
- Av-Ron, E., Byrne, J.H. and Baxter, D.A. Teaching basic principles of neuroscience with computer simulations. J. Undergrad. Neurosci. Edu., 4: A40-A52, 2006.
- Cai, Y., Flynn, M., Baxter, D.A. and Crow, T. Role of A-type K+ channels in spike broadening observed in soma and axon of Hermissenda type-B photo receptors: A simulation study. J. Comput. Neurosci., 21: 89-99, 2006.
- Baxter, D.A. and Byrne, J.H. Short-term plasticity in a computational model of the tail-withdrawal circuit in Aplysia. Neurocomput., 70: 1993-1999, 2007.
- Song, H., Smolen, P., Av-Ron, E., Baxter, D.A. and Byrne, J.H. Dynamics of a minimal model of interlocked positive and negative feedback loops of transcriptional regulation by cAMP-response element binding proteins. Biophy. J., 92: 3407-3424, 2007. PMID: 17277187
- Smolen, P., Baxter, D.A. and Byrne, J.H. Bistable MAP kinase activity: a plausible mechanism contributing to maintenance of late long-term potentiation. Am. J. Physiol. Cell Physiol., 294: C503-C515, 2008.
- Lorenzetti, F.D., Baxter, D.A., and Byrne, J.H. Molecular mechanisms underlying a cellular analogue of operant reward learning. Neuron, 59: 815-828, 2008.
- Mozzachiodi, R., Lorenzetti, F.D., Baxter, D.A., and Byrne, J.H. Changes in neuronal excitability serve as mechanism of long-term memory for operant conditioning. Nat. Neurosci., 10: 1146-1148, 2008.
- Smolen, P., Baxter, D.A. and Byrne, J.H. Interlocking dual-time feedback loops can enhance robustness to stochasticity and persistence of memory. Phys. Rev. E, 79: 031902, 2009.
- Zhang, Y., Smolen, P., Baxter, D.A. and Byrne, J.H. The sensitivity of memory consolidation and reconsolidation to inhibitors of protein synthesis and kinases. Learn Mem, 17: 428-439, 2010.
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