The multiplex structure of the mental lexicon influences picture naming in people with aphasia

Abstract

An emerging area of research in cognitive science is the utilization of networks to model the structure and processes of the mental lexicon in healthy and clinical populations, like aphasia. Previous research has focused on only one type of word similarity at a time (e.g., semantic relationships), even though words are multi-faceted. Here, we investigate lexical retrieval in a picture naming task from people with Broca’s and Wernicke’s aphasia and healthy controls by utilizing a multiplex network structure that accounts for the interplay between multiple semantic and phonological relationships among words in the mental lexicon. Extending upon previous work, we focused on the global network measure of closeness centrality which is known to capture spreading activation, an important process supporting lexical retrieval. We conducted a series of logistic regression models predicting the probability of correct picture naming. We tested whether multiplex closeness centrality was a better predictor of picture naming performance than single-layer closeness centralities, other network measures assessing local and meso-scale structure, psycholinguistic variables and group differences. We also examined production gaps, or the difference between the likelihood of producing a word with the lowest and highest closeness centralities. Our results indicated that multiplex closeness centrality was a significant predictor of picture naming performance, where words with high closeness centrality were more likely to be produced than words with low closeness centrality. Additionally, multiplex closeness centrality outperformed single-layer closeness centralities and other multiplex network measures, and remained a significant predictor after controlling for psycholinguistic variables and group differences. Furthermore, we found that the facilitative effect of closeness centrality was similar for both types of aphasia. Our results underline the importance of integrating multiple measures of word similarities in cognitive language networks for better understanding lexical retrieval in aphasia, with an eye towards future clinical applications.

Viability in Multiplex Lexical Networks and Machine Learning Characterizes Human Creativity

“…Multiplex networks represent a natural and suitable framework for this purpose, as they simultaneously encode multiple types of interaction among units of a complex networked system [49]. Therefore, multiplex lexical networks can be used to extract information about linguistic structures beyond information available from single-layer network analysis [9,[50][51][52][53].…”

“…The authors showed that the multiplex combination of different aspects of semantics and phonology boosted the lure of associates, a phenomenon where children tend to acquire new words that are similar to ones they already know, thus making the multiplex lexical representation of words in the mental lexicon a suitable tool for predicting early word acquisition [9,50,52]. The multiplex interplay between semantic, syntactic and phonological similarities of words also highlighted phonological priming effects [53] and critical differences in picture naming performance in patients with aphasia [51], a clinical condition affecting language understanding and production. Furthermore, examining the structure of this multiplex lexicon revealed a core of words that are highly connected to each other [10].…”

“…We represent word-word semantic and phonological similarities as a multiplex lexical network [9,10,51,53], where concepts are represented by nodes and are linked according to:…”

“…Only links elicited more than x ≥ 11 times were considered, in order for the association layer to feature the same link density of other multiplex layers. This layer is treated as undirected, as in previous approaches in cognitive network science [14,51]. • Synonyms [62], indicating overlap in meaning between concepts (e.g., "character" can mean also "font").…”

“…The resulting multiplex network included aspects of the mental lexicon such as phoneme overlap, meaning sharing, hierarchical generalizations, and semantic memory patterns, which were all reported to influence language processing and acquisition in both healthy [11,14,44,61,62] and clinical [46,48,51] populations. Based on recent results demonstrating how semantic memory structure relates to individual differences in creativity [20], we assume that the multilayer, networked representation of the mental lexicon serves as a valid approach to assess differences across our two levels of creativity groups.…”