Graph Analysis of Verbal Fluency Tests in Schizophrenia and Bipolar Disorder.

Adrian Andrzej Chrobak,Anna Starowicz-Filip,Karolina Machalska,Anna Julia Krupa,Marcin Siwek,Dominika Dudek,Aleksandra Arciszewska-Leszczuk,Aleksander Turek

doi:10.3390/brainsci12020166

Adrian Andrzej Chrobak, Anna Starowicz-Filip + Show 6 more

Open Access

https://doi.org/10.3390/brainsci12020166

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Abstract

Verbal Fluency Tests (VFT) are one of the most common neuropsychological tasks used in bipolar disorder (BD) and schizophrenia (SZ) research. Recently, a new VFT analysis method based on graph theory was developed. Interpreting spoken words as nodes and every temporal connection between consecutive words as edges, researchers created graph structures, allowing the extraction of more data from participants’ speech, called Speech Graph Attributes (SGA). The aim of our study was to compare speech graphs, derived from Phonemic and Semantic VFT, between SZ, BD, and healthy controls (HC). Twenty-nine SZ patients, twenty-nine BD patients, and twenty-nine HC performed Semantic and Phonemic VFT. Standard measures (SM) and 13 SGA were analyzed. SZ patients’ Semantic VFT graphs showed lower total word count and correct responses. Their graphs presented less nodes and edges, higher density, smaller diameter, average shortest path (ASP), and largest strongly connected component than the HC group. SM did not differentiate BD and HC groups, and patients’ Semantic VFT graphs presented smaller diameter and ASP than HC. None of the parameters differentiated BD and SZ patients. Our results encourage the use of speech graph analysis, as it reveals verbal fluency alterations that remained unnoticed in the routine comparisons of groups with the use SM.

Highlights

Schizophrenia (SZ) and bipolar disorder (BD) are severe mental disorders that share common symptom dimensions, neurophysiology, and genetics, and their treatment strategies are similar [1,2,3]
We have shown no significant differences between SZ, BD, and healthy controls (HC) groups in terms of Phonemic Verbal Fluency Tests (VFT) Speech Graph Attributes (SGA)
In our study, BD patients did not differ in terms of standard measures with HC, our results suggest that semantic VFT scores may be more sensitive than phonemic VFT to spot verbal fluency deficits in the group of relatively well performing BD individuals

Summary

Introduction

Schizophrenia (SZ) and bipolar disorder (BD) are severe mental disorders that share common symptom dimensions, neurophysiology, and genetics, and their treatment strategies are similar [1,2,3]. Both disorders are characterized by cognitive dysfunctions involving alteration of the structure of language. During VFT, participants are asked to name as many words as possible starting with a specific letter (Phonemic VFT), or belonging to a specific category, e.g., animals (Semantic VFT) Those tasks deliver information about the integrity of lexico-semantic memory and the ability to recall items from it, self-monitoring, inhibition of responses in adequate situations, and effortful self-initiation [6,7]

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