TR available

[David.Servan-Schreiber@A.GP.CS.CMU.EDU]

	A Parallel Distributed Processing Approach to 
           Behavior and Biology in Schizophrenia.

	Jonathan D. Cohen and David Servan-Schreiber

	          Technical Report AIP-100

    Department of Psychology and School of Computer Science
                       Carnegie Mellon
                    Pittsburgh, PA 15123


                           ABSTRACT

In this paper, we illustrate the use of connectionist models to explore the
relationship between biological variables and cognitive deficits in
schizophrenia.  In the first part of the paper, we describe schizophrenic
cognitive deficits in three experimental tasks that tap attention and
language processing abilities.  We also review biological disturbances that
have been reported involving the frontal lobes and the mesocortical dopamine
system.  In the second part of the paper we present three computer models,
each of which simulates normal performance in one of the cognitive tasks
described initially.  These models were developed within the connectionist
(or parallel distributed processing) framework.  At the behavioral level,
the models suggest that a disturbance in the processing of context can
account for schizophrenic patterns of performance in both attention and
language-related tasks.  At the same time, the models incorporate a
mechanism for processing context that can be identified with the function of
prefrontal cortex, and a parameter that corresponds to the neuromodulatory
effects of dopamine.  A disturbance in this parameter in the component of
the model corresponding to function of prefrontal cortex is sufficient to
account for schizophrenic patterns of performance in all three of the
cognitive tasks simulated.  Thus, the models offer an explanatory mechanism
linking performance deficits to a disturbance in the processing of context
which, in turn, is attributed to a reduction of dopaminergic activity in
prefrontal cortex.  In the General Discussion, we consider the implications
that these models have for our understanding of both normal and
schizophrenic cognition.  We conclude with a discussion of some general
issues concerning the use of computer simulation models in research.


This report is availble at no charge.  Please send requests to

             	 	jc5e at andrew.cmu.edu.