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Fronto-Pariatal connection asymmetry regulates working memory distractibility
KTH, School of Computer Science and Communication (CSC), Computational Biology, CB.
Karolinska Institutet, Stockholm.
Karolinska Institutet, Stockholm.
Karolinska Institutet, Stockholm.
2007 (English)In: Journal of Integrative Neuroscience, ISSN 0219-6352, Vol. 6, no 4, 567-596 p.Article in journal (Refereed) Published
Abstract [en]

Recent functional magnetic resonance imaging studies demonstrate that increased task-related neural activity in parietal and frontal cortex during development and training is positively correlated with improved visuospatial working memory (vsWM) performance. Yet, the analysis of the corresponding underlying functional reorganization of the fronto-parietal network has received little attention. Here, we perform an integrative experimental and computational analysis to determine the effective balance between the superior frontal sulcus (SFS) and intraparietal sulcus (IPS) and their putative role(s) in protecting against distracters. To this end, we performed electroencephalographic (EEG) recordings during a vsWM task. We utilized a biophysically based computational cortical network model to analyze the effects of different neural changes in the underlying cortical networks on the directed transfer function (DTF) and spiking activity. Combining a DTF analysis of our EEG data with the DTF analysis of the computational model, a directed strong SFS → IPS network was revealed. Such a configuration offers protection against distracters, whereas the opposite is true for strong IPS → SFS connections. Our results therefore suggest that the previously demonstrated improvement of vsWM performance during development could be due to a shift in the control of the effective balance between the SFS-IPS networks.

Place, publisher, year, edition, pages
2007. Vol. 6, no 4, 567-596 p.
Keyword [en]
Computational neuroscience; Connectivity; Cortico-cortical interactions; Directed transfer function; Distractibility; EEG; Frontal cortex; Neuronal circuits; Parietal cortex; Working memory
National Category
Biological Sciences
URN: urn:nbn:se:kth:diva-7809DOI: 10.1142/S0219635207001702ScopusID: 2-s2.0-38049042894OAI: diva2:12942
QC 20100705. Uppdaterad från InPress till Published i DiVA 20100705.Available from: 2007-12-12 Created: 2007-12-12 Last updated: 2010-09-21Bibliographically approved
In thesis
1. Neural Mechanisms Determining Visuospatial Working Memory Tasks: Biophysical Modeling, Functional MRI and EEG
Open this publication in new window or tab >>Neural Mechanisms Determining Visuospatial Working Memory Tasks: Biophysical Modeling, Functional MRI and EEG
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Visuospatial working memory (vsWM) is the ability to temporarily retain goal-relevant visuospatial information in memory. It is a key cognitive function related to general intelligence, and it improves throughout childhood and through WM training. Information is maintained in vsWM through persistent neuronal activity in a fronto-parietal network that consists of the intraparietal sulcus (IPS) and the frontal eye field (FEF). This network is regulated by the dorsolateral prefrontal cortex (dlPFC).

The features of brain structure and activity that regulate the access to and storage capacity of visuospatial WM (vsWM) are still unknown. The aim of my doctoral work has been to find such features by combining a biophysically based model of vsWM activity with functional MRI (fMRI) and EEG experiments.

In study I, we combined modeling and fMRI and showed that stronger fronto-parietal synaptic connections result in developmental increases in brain activity and in improved vsWM during development. This causal relationship was established by ruling out other previously suggested mechanisms, such as myelination or synaptic pruning,

In study II, we combined modeling and EEG to further explore the connectivity of the network. We showed that FEF→IPS connections are stronger than IPS→FEF connections, and that stimuli enter IPS. This arrangement of connections prevents distracting stimuli from being stored.

Study III was a theoretical study showing that errors in measurements of the amplitude of brain activity affect the estimation of effective connection strength.

In study IV, we analyzed EEG data from WM training in children with epilepsy. Improvements on the trained task were accompanied by increased frontal and parietal signal power, but not fronto-parietal coherence. This indicates that local changes in FEF and IPS could underlie improvements on the trained task.

dlPFC is important for the performance on a large variety of cognitive tasks.

In study V, we combined modeling with fMRI to test the hypothesis that dlPFC improves vsWM capacity by providing stabilizing excitatory inputs to IPS, and that dlPFC filters distracters by specifically lowering the capacity of neurons storing distracters. fMRI data confirmed the model hypothesis. We further showed that a dysfunctional dlPFC could explain the link between vsWM capacity and distractibility, as is found in ADHD. The model suggests that dlPFC carries out its multifaceted behavior not by performing advanced calculations itself, but by providing bias signals that control operations performed in the regions it connects to.

A specific aim of this thesis has been to describe the mechanistic model in a way that is accessible to people without a modeling background.

Place, publisher, year, edition, pages
Stockhollm: KTH, 2007. vi, 57 p.
Trita-CSC-A, ISSN 1653-5723 ; 2007:23
National Category
Computer Science
urn:nbn:se:kth:diva-4577 (URN)978-91-7178-832-0 (ISBN)
Public defence
2008-01-11, Sal D2, KTH, Lindstedtsvägen 5, Stockholm, 13:00
QC 20100705Available from: 2007-12-12 Created: 2007-12-12 Last updated: 2010-07-05Bibliographically approved

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