Publications

@article{Moller2017,
title = {Transcranial Electric Stimulation Can Impair Gains during Working Memory Training and Affects the Resting State Connectivity},
author = {Annie Möller and Federico Nemmi and Kim Karlsson and Torkel Klingberg},
doi = {10.3389/fnhum.2017.00364},
year = {2017},
date = {2017-01-01},
journal = {Frontiers in Human Neuroscience},
volume = {11},
number = {July},
pages = {1--12},
abstract = {Transcranial electric stimulation (tES) is a promising technique that has been shown to improve working memory (WM) performance and enhance the effect of cognitive training. However, experimental set up and electrode placement are not always determined based on neurofunctional knowledge about WM, leading to inconsistent results. Additional research on the effects of tES grounded on neurofunctional evidence is therefore necessary. 60 young, healthy, volunteers, assigned to 6 different groups, participated in 5 days of stimulation or sham treatment. 25 of these subjects also participated in MRI acquisition. We performed 3 experiments: In the first one we evaluated tES using either direct current stimulation (tDCS) with bilateral stimulation of the frontal or parietal lobe; in the second one we used the same tDCS protocol with a different electrode placement (i.e. supraorbital cathode); in the third one we used alternating currents (tACS) of 35 Hz, applied bilaterally to either the frontal or parietal lobes. The behavioral outcome measure was the WM capacity (i.e. number of remembered spatial position) during the 5 days of training. In a subsample of subjects we evaluated the neural effects of tDCS by measuring resting state connectivity with functional MRI, before and after the 5 days of tDCS and visuo-spatial WM training. We found a significant impairment of WM training-related gains associated with parietal tACS and frontal tDCS. Five days of tDCS stimulation was also associated with significant change in resting state connectivity revealed by multivariate pattern analysis (MVPA). None of the stimulation paradigms resulted in improved WM performance or enhanced WM training gains. These results show that tES can have negative effects on cognitive plasticity and affect resting-state functional connectivity.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Darki2015,
title = {The role of fronto-parietal and fronto-striatal networks in the development of working memory: A longitudinal study},
author = {Fahimeh Darki and Torkel Klingberg},
url = {https://academic.oup.com/cercor/article-lookup/doi/10.1093/cercor/bht352},
doi = {10.1093/cercor/bht352},
issn = {14602199},
year = {2015},
date = {2015-06-01},
journal = {Cerebral Cortex},
volume = {25},
number = {6},
pages = {1587--1595},
abstract = {The increase in working memory (WM) capacity is an important part of cognitive development during childhood and adolescence. Cross-sectional analyses have associated this development with higher activity, thinner cortex, and white matter maturation in fronto-parietal networks. However, there is still a lack of longitudinal data showing the dynamics of this development and the role of subcortical structures. We included 89 individuals, aged 6-25 years, who were scanned 1-3 times at 2-year intervals. Functional magnetic resonance imaging (fMRI) was used to identify activated areas in superior frontal, intraparietal cortices, and caudate nucleus during performance on a visuo-spatial WM task. Probabilistic tractography determined the anatomical pathways between these regions. In the cross-sectional analysis, WM capacity correlated with activity in frontal and parietal regions, cortical thickness in parietal cortex, and white matter structure [both fractional anisotropy (FA) and white matter volume] of fronto-parietal and fronto-striatal tracts. However, in the longitudinal analysis, FA in white matter tracts and activity in caudate predicted future WM capacity. The results show a dynamic of neural networks underlying WM development in which cortical activity and structure relate to current capacity, while white matter tracts and caudate activity predict future WM capacity.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Dumontheil2012,
title = {Brain activity during a visuospatial working memory task predicts arithmetical performance 2 years later},
author = {Iroise Dumontheil and Torkel Klingberg},
doi = {10.1093/cercor/bhr175},
issn = {10473211},
year = {2012},
date = {2012-01-01},
journal = {Cerebral Cortex},
volume = {22},
number = {5},
pages = {1078--1085},
abstract = {Visuospatial working memory (WM) capacity is highly correlated with mathematical reasoning abilities and can predict future development of arithmetical performance. Activity in the intraparietal sulcus (IPS) during visuospatial WM tasks correlates with interindividual differences in WM capacity. This region has also been implicated in numerical representation, and its structure and activity reflect arithmetical performance impairments (e.g., dyscalculia). We collected behavioral (N = 246) and neuroimaging data (N = 46) in a longitudinal sample to test whether IPS activity during a visuospatial WM task could provide more information than psychological testing alone and predict arithmetical performance 2 years later in healthy participants aged 6-16 years. Nonverbal reasoning and verbal and visuospatial WM measures were found to be independent predictors of arithmetical outcome. In addition, WM activation in the left IPS predicted arithmetical outcome independently of behavioral measures. A logistic model including both behavioral and imaging data showed improved sensitivity by correctly classifying more than twice as many children as poor arithmetical performers after 2 years than a model with behavioral measures only. These results demonstrate that neuroimaging data can provide useful information in addition to behavioral assessments and be used to improve the identification of individuals at risk of future low academic performance.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Ziermans2012,
title = {Working memory brain activity and capacity link MAOA polymorphism to aggressive behavior during development},
author = {T Ziermans and I Dumontheil and C Roggeman and M Peyrard-Janvid and H Matsson and J Kere and T Klingberg},
url = {http://dx.doi.org/10.1038/tp.2012.7},
doi = {10.1038/tp.2012.7},
issn = {21583188},
year = {2012},
date = {2012-01-01},
journal = {Translational Psychiatry},
volume = {2},
number = {2},
pages = {e85--9},
publisher = {Nature Publishing Group},
abstract = {A developmental increase in working memory capacity is an important part of cognitive development, and low working memory (WM) capacity is a risk factor for developing psychopathology. Brain activity represents a promising endophenotype for linking genes to behavior and for improving our understanding of the neurobiology of WM development. We investigated gene-brain-behavior relationships by focusing on 18 single-nucleotide polymorphisms (SNPs) located in six dopaminergic candidate genes (COMT, SLC6A3/DAT1, DBH, DRD4, DRD5, MAOA). Visuospatial WM (VSWM) brain activity, measured with functional magnetic resonance imaging, and VSWM capacity were assessed in a longitudinal study of typically developing children and adolescents. Behavioral problems were evaluated using the Child Behavior Checklist (CBCL). One SNP (rs6609257), located ~6.6 kb downstream of the monoamine oxidase A gene (MAOA) on human chromosome X, significantly affected brain activity in a network of frontal, parietal and occipital regions. Increased activity in this network, but not in caudate nucleus or anterior prefrontal regions, was correlated with VSWM capacity, which in turn predicted externalizing (aggressive/oppositional) symptoms, with higher WM capacity associated with fewer externalizing symptoms. There were no direct significant correlations between rs6609257 and behavioral symptoms. These results suggest a mediating role of WM brain activity and capacity in linking the MAOA gene to aggressive behavior during development.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{Olesen2007,
title = {Brain activity related to working memory and distraction in children and adults},
author = {Pernille J Olesen and Julian Macoveanu and Jesper Tegnér and Torkel Klingberg},
doi = {10.1093/cercor/bhl014},
issn = {10473211},
year = {2007},
date = {2007-01-01},
journal = {Cerebral Cortex},
volume = {17},
number = {5},
pages = {1047--1054},
abstract = {In order to retain information in working memory (WM) during a delay, distracting stimuli must be ignored. This important ability improves during childhood, but the neural basis for this development is not known. We measured brain activity with functional magnetic resonance imaging in adults and 13-year-old children. Data were analyzed with an event-related design to isolate activity during cue, delay, distraction, and response selection. Adults were more accurate and less distractible than children. Activity in the middle frontal gyrus and intraparietal cortex was stronger in adults than in children during the delay, when information was maintained in WM. Distraction during the delay evoked activation in parietal and occipital cortices in both adults and children. However, distraction activated frontal cortex only in children. The larger frontal activation in response to distracters presented during the delay may explain why children are more susceptible to interfering stimuli.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}