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Contact Information:
Division of Basic Biomedical Sciences
Sanford School of Medicine of The University of South Dakota
414 E.Clark Street
Vermillion, SD 57069
phone: (605)-677-5254
fax: (605)-677-6381
biomed@usd.edu
Last Modified: 08/24/07
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Research Interests: Cellular Mechanisms of Learning and Memory
The focus of Dr. Burrell's research is to understand how plasticity in neurons underlies changes in behavior during learning and subsequent memory formation. Specifically, he studies the cellular mechanisms of learning using the medicinal leech, Hirudo medicinalis as a model system. The goal of this project is to elucidate the distinct cellular mechanisms for various forms of neuromodulation (what second messenger pathways are involved, which ion channels are modulated, etc.) and to investigate how these processes might contribute to more complex forms of learning.
Dr. Burrell's laboratory also examines the role of activity-dependent changes in synaptic transmission by afferent neurons onto the S-cell, specifically long-term potentiation (LTP) and long-term depression (LTD), which are thought play an important role during associative learning. In the leech, his team has observed several forms of LTP and LTD in connections made by both touch- and pressure-sensitive mechanosensory neurons onto the S-cell. Currently, they are examining the cellular mechanisms of these various forms of synaptic plasticity in more detail using in vitro experiments as well as investigating the role of theses synaptic changes in behaviorally-intact preparations. A future goal is to determine whether serotonergic modulation of excitability interacts with these activity-dependent synaptic changes.
A third area of study in the lab focuses on modulation of gap junctions that form electrical synapses in the brain. One role of these electrical synapses is to coordinate and synchronize activity in a network of interconnected neurons within the brain. The S-cells we study are connected to each other by electrical synapses that allow action potentials to propagate through the entire S-cell network, allowing the network to have a unified output to follower cells throughout the leech CNS. Recent work by Dr. Brenda Moss and myself has shown that these electrical synapses are modulated by serotonin. As demonstrated in a computational model of the S-cell network, the effect of this modulation is to increase the instantaneous frequency of S-cell activity as it propagates through the CNS. These results show that modulation of gap junctions can significantly alter the pattern of activity within an electrically coupled neural network.
The S-cell model can be accessed at: http://senselab.med.yale.edu/SenseLab/ModelDB/ShowModel.asp?model=53559
Publications
Brian D. Burrell and Christie L. Sahley (2005). Serotonin Mediates Learning-induced Potentiation of Excitability. Journal of Neurophysiology 94:4002-4010.
Brenda L. Moss, Abby D. Fuller, Christie L. Sahley, Brian D. Burrell (2005). Serotonin Modulates Axo-axonal Coupling Between Neurons Critical for Learning in the Leech. Journal of Neurophsiology 94:2575-2589.
Burrell BD, Sahley CL (2004). Multiple forms of long-term potentiation and long-term depression that converge on a single interneuron in the CNS of the medicinal leech. Journal of Neuroscience 24:4011-4019.
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