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    COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
        Institute for Computational Sciences and Informatics
       	  CSI 929  (http://csi.gmu.edu/lcdm/seminar/schedule.html)
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 Learning and Memory: a Computational Approach to Calcium Dynamics

			    Avrama Blackwell
 Institute for Computational Sciences and Informatics, George Mason University
				 and
	   ERIM/Environmental Research Institute, Arlington, VA 
			 
Hermissenda crassicornis is a small, shell-less marine snail that can be
classically conditioned to associate light (the conditioned stimulus) with
turbulence (the unconditioned stimulus).  The memory of the association is
stored in the medial type B photoreceptor cell, which both transduces the
light stimulus, and receives direct inhibitory synaptic input from the
statocyst, which transduces the turbulence.  The form of memory storage
consists of an increase in the resistance across the membrane, which
results in a larger increase in voltage across the membrane in response to
light.  Memory storage is critically dependent on elevation of
intracellular calcium, and subsequent activation of protein kinase C,
which causes a long term reduction in two voltage-dependent potassium
currents (Alkon 1984).  

Many biochemical processes affect intracellular calcium concentration:
calcium diffusion, buffering and light activated release from
intracellular stores.  These processes are modeled with differential
equations, and simulated using GENESIS, a neural modeling software
package.  Simulations show that release of calcium from intracellular
stores is a significant source of calcium in the soma and may be the
activating signal for the light induced potassium current. 
                         
                          Monday , February 24, 1997
                                  4:30 pm
                          Room 206, Science & Tech. I
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