P01-381 - A Model of Manic Thought Disorder Using a Semantic Network and Disordered Thread Salience

Manic thought disorder (MTD) may arise from an inappropriate assignment of salience to threads scanning the semantic network, rather than from a disordered lexicon alone. The authors modeled the mental lexicon as a semantic network and simulated thought generation as a walk along this directed graph. By assigning weights to vertices and edges, they replicated features of MTD including pressure of speech, clang associations, and flight-of-ideas. The model proposes that antipsychotics reduce inappropriate thread salience, leading to the disappearance of MTD. The authors argue that understanding MTD is important for revealing the mental computational processes underlying normal thought and its disorders.

Study at a glance

Abstract

IntroductionManic Thought Disorder (MTD) is a characteristic clinical feature of mania. In the past, explanations of its pathogenesis have ranged from hypotheses of a disordered lexicon, to the side effects of a fatuous affect. We previously modeled thought disorder in schizophrenia using the notion of threads of thought.ObjectivesTo examine the nature of MTD to see if it is consistent with the theory of a disordered lexicon alone.AimsTo simulate the mental lexicon and thought generation and examine if computational lesioning experiments could simulate various aspects of MTD.MethodsWe modeled the mental lexicon as a semantic network using the programming language Mathematica®. Thought generation was modeled as a walk along this directed graph. Semantic priming was implemented as assigned weights; these weights in turn determined assignment of salience to threads scanning the network.ResultsAssignment of weights to the vertices and/or edges of the graph allows us to simulate the flow and trajectory of speech permitting the replication of features of MTD including pressure of speech, clang associations and flight-of-ideas.ConclusionsOur model of MTD allows us to propose that thought disorder in mania occurs due to an inappropriate assignment of salience to threads scanning the semantic network. Reduction of inappropriate thread salience by antipsychotics must result in a disappearance of MTD. While MTD is interesting to listen to, for anyone, it betrays the underlying mental computational processes involved in the generation of normal thought and MTD and hence very important for psychiatrists and cognitive scientists.