Impact of Working Memory Load on fMRI Resting State Pattern in Subsequent Resting Phases

Abstract

BackgroundThe default-mode network (DMN) is a functional network with increasing relevance for psychiatric research, characterized by increased activation at rest and decreased activation during task performance. The degree of DMN deactivation during a cognitively demanding task depends on its difficulty. However, the relation of hemodynamic responses in the resting phase after a preceding cognitive challenge remains relatively unexplored. We test the hypothesis that the degree of activation of the DMN following cognitive challenge is influenced by the cognitive load of a preceding working-memory task.Methodology/Principal FindingsTwenty-five healthy subjects were investigated with functional MRI at 3 Tesla while performing a working-memory task with embedded short resting phases. Data were decomposed into statistically independent spatio-temporal components using Tensor Independent Component Analysis (TICA). The DMN was selected using a template-matching procedure. The spatial map contained rest-related activations in the medial frontal cortex, ventral anterior and posterior cingulate cortex. The time course of the DMN revealed increased activation at rest after 1-back and 2-back blocks compared to the activation after a 0-back block.Conclusion/SignificanceWe present evidence that a cognitively challenging working-memory task is followed by greater activation of the DMN than a simple letter-matching task. This might be interpreted as a functional correlate of self-evaluation and reflection of the preceding task or as relocation of cerebral resources representing recovery from high cognitive demands. This finding is highly relevant for neuroimaging studies which include resting phases in cognitive tasks as stable baseline conditions. Further studies investigating the DMN should take possible interactions of tasks and subsequent resting phases into account.

Neural processing of criticism and positive comments from relatives in individuals with schizotypal personality traits

“…Greater activation of the left superior and middle frontal gyri and bilateral PCC during criticism more than during neutral comments across all participants, may be explained by the role of the superior and middle temporal gyri in negative emotion regulation (Ochsner and Gross 2005;Mak et al 2009), and the PCC in cognitive control of aversive stimuli (Koenigsberg et al 2010), self-evaluation of past performance (Pyka et al 2009). PCC activity is often observed in the default-mode network for working memory (Fransson and Marrelec 2008;Pyka et al 2009), as well as self-referential processing (Kumari et al 2010;Sajonz et al 2010).…”

“…Similarly, the rostral anterior cingulate cortex (ACC) is involved in appraisal of emotional information (Ochsner and Gross 2005;Kalisch et al 2006;Polli et al 2008), specifi cally negatively valenced material (Kalisch et al 2006;Mak et al 2009), as well as confl ict detection during tasks such as emotional Stroop interference (Mohanty et al 2007). The posterior cingulate cortex (PCC) is involved in cognitive control of aversive stimuli (Koenigsberg et al 2010) and self-evaluation (Pyka et al 2009;Sajonz et al 2010). In contrast, response to positively valenced material may engage dopaminergic reward areas, such as the striatum.…”

“…PCC activity is often observed in the default-mode network for working memory (Fransson and Marrelec 2008;Pyka et al 2009), as well as self-referential processing (Kumari et al 2010;Sajonz et al 2010). When listening to relative criticism, individuals may engage in cognitive appraisal, rather than emotional processing, and self-refl ection of such personallydirected information.…”

Impaired language function in generalized epilepsy: Inadequate suppression of the default mode network

“…In previous studies it has been shown that the more difficult the task, the greater the negative BOLD response in DMN [27,28,29]. Task difficulty can be modulated parametrically by e.g.…”

Neuronal oscillations in the EEG under varying cognitive load: A comparative study between slow waves and faster oscillations

“…One way to ensure this is to adopt an experimental set-up that enables us to compare the VLF EEG under different levels of stimulation, whilst keeping everything else constant (same participants and same analysis methods). Other paradigms such as working memory tasks which manipulate memory load (Pyka et al, 2009), and simple choice reaction time attention tasks (Helps et al, :2010 could also be implemented and the oscillations contrasted with the same methodology. It would be interesting to include experimental tasks with more frequent sampling (i.e.…”