Variations in working memory capacity: From cognition to brain networks

Working memory capacity (WMC) predicts our ability to acquire knowledge and develop new skills, and is a better predictor of academic achievement than IQ. The research described in this thesis was motivated by one of the cognitive theories of WM – the executive-attention theory of WMC. The theory suggests a close relationship between individual’s WMC and attention control abilities in the face of interference from habitual action routines, environmental distractors, or thoughts that are irrelevant for the task at hand (i.e. task-unrelated thoughts or mind wandering). In this thesis, we exploited the often-observed relationship between WMC and performance in response-conflict tasks (e.g., Simon task, Eriksen flanker task), which challenge one’s ability to maintain task goals in the face of distraction. By characterizing the relationship between WMC and cognitive control abilities combining different analyses and experimental approaches we sought to extend WMC research from cognitive to the neural level. In summary, results described in this thesis point to the need to update existing cognitive theories of WMC with neurophysiological findings from fMRI and EEG, as existing descriptive cognitive models are too under-specified to explain the richness and complexity of phenomena related to individual variations in WMC.