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Unity and diversity of tonic and phasic executive control in episodic and working memory
Umeå University, Faculty of Social Sciences, Department of Psychology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
Cognitive Neurophysiology Research Group, Department of Clinical Neuroscience, Karolinska Institute, Sweden.
Center for Cognitive Neuroscience, Duke University, USA.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
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2007 (English)In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 36, no 4, 1361-1373 p.Article in journal (Refereed) Published
Abstract [en]

The present study aimed to delineate the extent to which unitary executive functions might be shared across the separate domains of episodic and working memory. A mixed blocked/event-related functional magnetic resonance imaging (fMRI) design was employed to assess sustained (tonic control) and transient (phasic control) brain responses arising from incrementing executive demand (source versus item episodic memory - vis-à-vis - two-back versus one-back working memory) using load-dependent activation overlaps as indices of common components. Although an extensive portion of the regional load effects constituted differential control modulations in both sustained and transient responses, commonalities were also found implicating a subset of executive core mechanisms consistent with unitary or domain general control. 'Unitary' control modulations were temporally dissociated into (1) shared tonic components involving medial and lateral prefrontal cortex, striatum, cerebellum and superior parietal cortex, assumed to govern enhanced top-down context processing, monitoring and sustained attention throughout task periods and (2) stimulus-synchronous phasic components encompassing posterior intraparietal sulcus, hypothesized to support dynamic shifting of the 'focus of attention' among internal representations. Taken together, these results converge with theoretical models advocating both unity and diversity among executive control processes.

Place, publisher, year, edition, pages
Elsevier , 2007. Vol. 36, no 4, 1361-1373 p.
National Category
Physiology Psychology
Research subject
URN: urn:nbn:se:umu:diva-5199DOI: 10.1016/j.neuroimage.2007.03.058PubMedID: 17524668OAI: diva2:144616
Available from: 2006-05-19 Created: 2006-05-19 Last updated: 2011-06-21Bibliographically approved
In thesis
1. Cross-functional brain imaging of attention, memory, and executive functions: Unity and diversity of neurocognitive component processes
Open this publication in new window or tab >>Cross-functional brain imaging of attention, memory, and executive functions: Unity and diversity of neurocognitive component processes
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The central theme of the present thesis revolves around the exploration of similarities and differences in brain activity patterns invoked by the component processes underlying mnemonic, executive and attentional functions. The primary aim was to identify and functionally characterize commonly recruited brain regions in terms of shared component processes, which has been a largely neglected area of research in cognitive neuroscience. The vast majority of functional brain imaging investigations of cognition has focused on delineating differences between cognitive functions or processes, with the purpose of isolating the unique functional neuroanatomy that underlies specific cognitive domains. By contrast, the present thesis builds on the results from three imaging studies that focused primarily on detecting commonalities in functional brain activity across different forms of memory processes. In study I, the imaging data from two positron emission tomography (PET) experiments were re-analyzed to identify common activation patterns associated with nine different memory tasks incorporated across the experiments, three each separately indexing working memory, episodic memory, and semantic memory. A generic prefrontal cortex (PFC) network involving discrete subregions of the left hemisphere located in ventrolateral (BA 45/47), dorsolateral (BA 9/44/46), and frontopolar (BA 10) sectors of PFC, as well as a midline portion of the frontal lobes, encompassing the dorsal part of the anterior cingulate cortex (ACC) (BA 24/32), was conjointly recruited across all tasks. In study II, we used a novel mixed blocked/event-related functional magnetic resonance imaging (fMRI) design, which enables separation of brain responses associated with different temporal dynamics to further investigate commonalities of neural activation across working memory, episodic memory, semantic memory, and attention/vigilance. A similar set of common PFC regions, as that discovered in Study I, was found to elicit overlapping brain activity across all memory tasks, with a subset of regions also activated in the attention/vigilance task. Furthermore, the task-induced brain activity was dissociated in terms of the temporal profiles of the evoked neural responses. A common pattern of sustained activity seen across all memory tasks and the attention task involved bilateral (predominantly right-lateralized) ventrolateral PFC (BA 45/47), and the dorsal ACC (BA 24/32), which was assumed to reflect general processes of attention/vigilance. A pattern of sustained activity elicited in all memory tasks, in the absence of attention-related activity, involved the right frontopolar cortex (BA 10), which was assumed to reflect control processes underlying task set maintenance. In addition, common transient activation evoked in the memory tasks relative to the attention task was found in the dorsolateral (BA 9/44) and ventrolateral (BA 47) PFC, the superior parietal cortex (BA 7), and cerebellum. In study III, a mixed fMRI design was used to assess the degree of common brain activity associated with increased executive demand, which was independently manipulated within episodic and working memory. Unitary control modulations involved a shared tonic executive component subserved by fronto-striatal-cerebellar circuitry, assumed to govern top-down context processing throughout task periods, and a stimulus-synchronous phasic component mediated by the intraparietal sulcus (BA 7), assumed to support dynamic shifting of the ‘focus of attention’ among internal representations. Collectively, the theoretical implications of shared neural mechanisms are discussed, with a special focus on human memory and its multifaceted relationships with attention and executive control functions. Finally, the presented imaging data are used to outline a tentative hierarchical neurocognitive model that attempts to give an account of how different unitary component processes might work together during cognitive task performance.

Place, publisher, year, edition, pages
Umeå: Psykologi, 2006. 69 p.
Human memory, executive functions, prefrontal cortex, sustained and transient neural activity, declarative long-term memory, attention, working memory, functional neuroimaging, cognitive control.
National Category
urn:nbn:se:umu:diva-805 (URN)91-7264-107-X (ISBN)
Public defence
2006-06-01, Hörsal E, Humanisthuset, Umeå universitet, Umeå, 10:15
Available from: 2006-05-19 Created: 2006-05-19 Last updated: 2011-01-25Bibliographically approved

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