Connectionists: New paper. Why trace and delay conditioning are sometimes (but not always) hippocampal dependent: A computational model

[Mark Gluck]

Dear Colleagues, 

A newly published paper has been uploaded to our website at: http://www.gluck.edu/pdf/2013_MoustafaHippModel2013.pdf

Moustafa,  A. A., Wufong, E., Servatius, R. J., Pang,  K. C., Gluck,  M. A., & Myers,  C. E. (2013). Why trace and delay conditioning are sometimes (but not always) hippocampal dependent: A computational model. Brain Research. 1493: 48-67. 

ABSTRACT: A recurrent-network model provides a unified account of the hippocampal
region in mediating the representation of temporal information in classical
eyeblink conditioning. Much empirical research is consistent with a general
conclusion that delay conditioning (in which the conditioned stimulus CS and
unconditioned stimulus US overlap and co-terminate) is independent of the
hippocampal system, while trace conditioning (in which the CS terminates
before US onset) depends on the hippocampus. However, recent studies show
that, under some circumstances, delay conditioning can be
hippocampal-dependent and trace conditioning can be spared following
hippocampal lesion. Here, we present an extension of our prior trial-level
models of hippocampal function and stimulus representation (Gluck & Myers,
1993, 2001) that can explain these findings within a unified framework.
Specifically, the current model includes adaptive recurrent collateral
connections that aid in the representation of intra-trial temporal
information. With this model, as in our prior models, we argue that the
hippocampus is not specialized for conditioned response timing, but rather
is a general-purpose system that learns to predict the next state of all
stimuli given the current state of variables encoded by activity in
recurrent collaterals. As such, the model correctly predicts that
hippocampal involvement in classical conditioning should be critical not
only when there is an intervening trace interval, but also when there is a
long delay between CS onset and US onset. Our model simulates empirical data
from many variants of classical conditioning, including delay and trace
paradigms in which the length of the CS, the inter-stimulus interval, or the
trace interval is varied. Finally, we discuss model limitations, future
directions, and several novel empirical predictions of this temporal
processing model of hippocampal function and learning.


Comments and feedback are always welcome and appreciated. 

- Mark Gluck

___________________________________
Dr. Mark A. Gluck,  Professor  
  Director, Rutgers Memory Disorders Project  
Center for Molecular  and Behavioral Neuroscience
Rutgers University                                
197 University Ave.                                   
Newark, New Jersey  07102                  
 	 Web:  http://www.gluck.edu
	 Email:  gluck at pavlov.rutgers.edu
    	Ph:  (973) 353-3298
 
     












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