The Roles of Working Memory and Executive Functioning in Relational Semantic Processing Tasks: Evidence from Primary...

Referential semantic processing tasks, such as word-picture matching (WPM), require the matching of stimuli that represent the same concept, while relational semantic processing tasks, such as Pyramids and Palm Trees (PPT), require the processing of relationships between concepts. Compared to referential tasks, relational tasks may be likely to place a greater demand on working memory and/or executive functioning. In the current study, we examined referential and relational semantic processing in all variants of primary progressive aphasia (PPA). We predicted that backward digit and spatial span tasks and/or Trails B would be significant predictors of accuracy on relational tasks, while similar tasks that place less significant demands on working memory or executive functioning, such as forward digit and spatial span tasks and Trails A, would not be significant predictors of accuracy on relational tasks. In behavioral regression analyses, neither backward span task was a significant predictor of accuracy on referential tasks, but accuracy on 5 out of 6 relational tasks was predicted by at least one backward span task. In a second set of behavioral analyses, neither Trails task was a significant predictor of accuracy on referential tasks. Conversely, accuracy on 5 out of 6 relational tasks was predicted by Trails B. In regression analyses involving grey matter volume, three ROIs (left middle temporal gyrus, left insula, right middle temporal pole) were significant positive predictors of accuracy on a referential task (Auditory WPM). The same three ROIs were significant positive predictors of accuracy on a relational task (PPT-Pictures), along with one additional ROI - the left pars triangularis. The findings of this study suggest that performance on relational semantic processing tasks is affected by working memory capacity and executive functioning, which are supported by the left pars triangularis.