Publications by authors named "Patrick Dupont"

151 Publications

Baseline cognition is the best predictor of 4-year cognitive change in cognitively intact older adults.

Alzheimers Res Ther 2021 04 7;13(1):75. Epub 2021 Apr 7.

Laboratory for Cognitive Neurology, Department of Neurosciences, Leuven Brain Institute, KU Leuven, Leuven, Belgium.

Background: We examined in cognitively intact older adults the relative weight of cognitive, genetic, structural and amyloid brain imaging variables for predicting cognitive change over a 4-year time course.

Methods: One hundred-eighty community-recruited cognitively intact older adults (mean age 68 years, range 52-80 years, 81 women) belonging to the Flemish Prevent Alzheimer's Disease Cohort KU Leuven (F-PACK) longitudinal observational cohort underwent a baseline evaluation consisting of detailed cognitive assessment, structural MRI and F-flutemetamol PET. At inclusion, subjects were stratified based on Apolipoprotein E (APOE) ε4 and Brain-Derived Neurotrophic Factor (BDNF) val66met polymorphism according to a factorial design. At inclusion, 15% were amyloid-PET positive (Centiloid >23.4). All subjects underwent 2-yearly follow-up of cognitive performance for a 4-year time period. Baseline cognitive scores were analysed using factor analysis. The slope of cognitive change over time was modelled using latent growth curve analysis. Using correlation analysis, hierarchical regression and mediation analysis, we examined the effect of demographic (age, sex, education) and genetic variables, baseline cognition, MRI volumetric (both voxelwise and region-based) as well as amyloid imaging measures on the longitudinal slope of cognitive change.

Results: A base model of age and sex explained 18.5% of variance in episodic memory decline. This increased to 41.6% by adding baseline episodic memory scores. Adding amyloid load or volumetric measures explained only a negligible additional amount of variance (increase to 42.2%). A mediation analysis indicated that the effect of age on episodic memory scores was partly direct and partly mediated via hippocampal volume. Amyloid load did not play a significant role as mediator between age, hippocampal volume and episodic memory decline.

Conclusion: In cognitively intact older adults, the strongest baseline predictor of subsequent episodic memory decline was the baseline episodic memory score. When this score was included, only very limited explanatory power was added by brain volume or amyloid load measures. The data warn against classifications that are purely biomarker-based and highlight the value of baseline cognitive performance levels in predictive models.
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http://dx.doi.org/10.1186/s13195-021-00798-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8028179PMC
April 2021

Predictive value of metabolic and perfusion changes outside the seizure onset zone for postoperative outcome in patients with refractory focal epilepsy.

Acta Neurol Belg 2021 Feb 5. Epub 2021 Feb 5.

Division of Nuclear Medicine, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium.

The value of functional molecular changes outside the seizure onset zone as independent predictive factors of surgical outcome has been scarcely evaluated. The aim of this retrospective study was to evaluate relative metabolic and perfusion changes outside the seizure onset zone as predictors of postoperative outcome in patients with unifocal refractory focal epilepsy. Eighty-six unifocal epilepsy patients who underwent F-FDG PET prior to surgery were included. Ictal and interictal perfusion SPECT was available in 65 patients. Good postoperative outcome was defined as the International League against Epilepsy class 1. Using univariate statistical analysis, the predictive ability of volume-of-interest based relative metabolism/perfusion for outcome classification was quantified by AUC ROC-curve, using composite, unilateral cortical (frontal, orbitofrontal, temporal, parietal, occipital) and central volumes-of-interest. The results were cross-validated, and a false discovery rate (FDR) correction was applied. As a secondary objective, a subgroup analysis was performed on temporal lobe epilepsy patients (N = 64). Increased relative ictal perfusion in the contralateral central volume-of-interest was significantly associated with the good surgical outcome both in the total population (AUC 0.79, p = 0.009) and the temporal lobe epilepsy subgroup (AUC 0.80, p = 0.028). No other significant associations between functional molecular changes and postoperative outcome were found. Increased relative ictal perfusion in the contralateral central region significantly predicted outcome after epilepsy surgery in patients with refractory focal epilepsy. We postulate that these relative perfusion changes could be an expression of better preoperative neuronal network integration and centralization in the contralateral central structures, which is suggested to be associated with better postoperative outcome.
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http://dx.doi.org/10.1007/s13760-020-01569-yDOI Listing
February 2021

A Role of PET/MR Imaging in Dementia?

Authors:
Patrick Dupont

Semin Nucl Med 2021 May 30;51(3):296-302. Epub 2021 Jan 30.

KU Leuven, Leuven Brain Institute, Department of Neurosciences, Laboratory for Cognitive Neurology, Leuven, Belgium; University of Stellenbosch, Department of Nuclear Medicine, Cape Town, South Africa. Electronic address:

Since many years, magnetic resonance imaging (MRI) and positron emission tomography (PET) have a prominent role in neurodegenerative disorders and dementia, not only in a research setting but also in a clinical setting. For several decades, information from both modalities is combined ranging from individual visual assessments to fully integrating all images. Several tools are available to coregister images from MRI and PET and to covisualize these images. When studying neurodegenerative disorders with PET it is important to perform a partial volume correction and this can be done using the structural information obtained by MRI. With the advent of PET/MR, the question arises in how far this hybrid imaging modality is an added value compared to combining PET and MRI data from two separate modalities. One issue in PET/MR is still not yet completely settled, that is, the attenuation correction. This is of less importance for visual assessments but it can become an issue when combining data from PET/CT and PET/MR scanners in multicenter studies or when using cut-off values to classify patients. Simultaneous imaging has clearly some advantages: for the patient it is beneficial to have only one scan session instead of two but also in cases in which PET data are related to functional of physiological data acquired with MRI (such as functional MRI or arterial spin labeling). However, the most important benefit is currently the more integrated use of PET and MRI. This is also possible with separate measurements but requires more streamlining of the whole process. In that case coregistration of images is mandatory. It needs to be determined in which cases simultaneous PET/MRI leads to new insights or improved diagnosis compared to multimodal imaging using dedicated scanners.
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http://dx.doi.org/10.1053/j.semnuclmed.2021.01.003DOI Listing
May 2021

Virtual brain grafting: Enabling whole brain parcellation in the presence of large lesions.

Neuroimage 2021 04 14;229:117731. Epub 2021 Jan 14.

KU Leuven, Department of Imaging and Pathology, Translational MRI, Leuven, Belgium; KU Leuven, Leuven Brain Institute (LBI), Department of Neurosciences, Leuven, Belgium; UZ Leuven, Department of Radiology, Leuven, Belgium.

Brain atlases and templates are at the heart of neuroimaging analyses, for which they facilitate multimodal registration, enable group comparisons and provide anatomical reference. However, as atlas-based approaches rely on correspondence mapping between images they perform poorly in the presence of structural pathology. Whilst several strategies exist to overcome this problem, their performance is often dependent on the type, size and homogeneity of any lesions present. We therefore propose a new solution, referred to as Virtual Brain Grafting (VBG), which is a fully-automated, open-source workflow to reliably parcellate magnetic resonance imaging (MRI) datasets in the presence of a broad spectrum of focal brain pathologies, including large, bilateral, intra- and extra-axial, heterogeneous lesions with and without mass effect. The core of the VBG approach is the generation of a lesion-free T1-weighted image, which enables further image processing operations that would otherwise fail. Here we validated our solution based on Freesurfer recon-all parcellation in a group of 10 patients with heterogeneous gliomatous lesions, and a realistic synthetic cohort of glioma patients (n = 100) derived from healthy control data and patient data. We demonstrate that VBG outperforms a non-VBG approach assessed qualitatively by expert neuroradiologists and Mann-Whitney U tests to compare corresponding parcellations (real patients U(6,6) = 33, z = 2.738, P < .010, synthetic-patients U(48,48) = 2076, z = 7.336, P < .001). Results were also quantitatively evaluated by comparing mean dice scores from the synthetic-patients using one-way ANOVA (unilateral VBG = 0.894, bilateral VBG = 0.903, and non-VBG = 0.617, P < .001). Additionally, we used linear regression to show the influence of lesion volume, lesion overlap with, and distance from the Freesurfer volumes of interest, on labeling accuracy. VBG may benefit the neuroimaging community by enabling automated state-of-the-art MRI analyses in clinical populations using methods such as FreeSurfer, CAT12, SPM, Connectome Workbench, as well as structural and functional connectomics. To fully maximize its availability, VBG is provided as open software under a Mozilla 2.0 license (https://github.com/KUL-Radneuron/KUL_VBG).
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http://dx.doi.org/10.1016/j.neuroimage.2021.117731DOI Listing
April 2021

Quantitative MRI phenotypes capture biological heterogeneity in multiple sclerosis patients.

Sci Rep 2021 Jan 15;11(1):1573. Epub 2021 Jan 15.

Laboratory for Neuroimmunology, Department of Neurosciences, KU Leuven, Herestraat 49, Box 1022, 3000, Leuven, Belgium.

Magnetization transfer ratio (MTR) and brain volumetric imaging are (semi-)quantitative MRI markers capturing demyelination, axonal degeneration and/or inflammation. However, factors shaping variation in these traits are largely unknown. In this study, we collected a longitudinal cohort of 33 multiple sclerosis (MS) patients and extended it cross-sectionally to 213. We measured MTR in lesions, normal-appearing white matter (NAWM), normal-appearing grey matter (NAGM) and total brain, grey matter, white matter and lesion volume. We also calculated the polygenic MS risk score. Longitudinally, inter-patient differences at inclusion and intra-patient changes during follow-up together explained > 70% of variance in MRI, with inter-patient differences at inclusion being the predominant source of variance. Cross-sectionally, we observed a moderate correlation of MTR between NAGM and NAWM and, less pronounced, with lesions. Age and gender explained about 30% of variance in total brain and grey matter volume. However, they contributed less than 10% to variance in MTR measures. There were no significant associations between MRI traits and the genetic risk score. In conclusion, (semi-)quantitative MRI traits change with ongoing disease activity but this change is modest in comparison to pre-existing inter-patient differences. These traits reflect individual variation in biological processes, which appear different from those involved in genetic MS susceptibility.
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http://dx.doi.org/10.1038/s41598-021-81035-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7811013PMC
January 2021

In vivo synaptic density relates to glucose metabolism at rest in healthy subjects, but is strongly modulated by regional differences.

J Cereb Blood Flow Metab 2021 Jan 14:271678X20981502. Epub 2021 Jan 14.

Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.

Preclinical and postmortem studies have suggested that regional synaptic density and glucose consumption (CMRGlc) are strongly related. However, the relation between synaptic density and cerebral glucose metabolism in the human brain has not directly been assessed in vivo. Using [C]UCB-J binding to synaptic vesicle glycoprotein 2 A (SV2A) as indicator for synaptic density and [F]FDG for measuring cerebral glucose consumption, we studied twenty healthy female subjects (age 29.6 ± 9.9 yrs) who underwent a single-day dual-tracer protocol (GE Signa PET-MR). Global measures of absolute and relative CMRGlc and specific binding of [C]UCB-J were indeed highly significantly correlated ( > 0.47,  < 0.001). However, regional differences in relative [F]FDG and [C]UCB-J uptake were observed, with up to 19% higher [C]UCB-J uptake in the medial temporal lobe (MTL) and up to 17% higher glucose metabolism in frontal and motor-related areas and thalamus. This pattern has a considerable overlap with the brain regions showing different levels of aerobic glycolysis. Regionally varying energy demands of inhibitory and excitatory synapses at rest may also contribute to this difference. Being unaffected by astroglial and/or microglial energy demands, changes in synaptic density in the MTL may therefore be more sensitive to early detection of pathological conditions compared to changes in glucose metabolism.
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http://dx.doi.org/10.1177/0271678X20981502DOI Listing
January 2021

Augmenting interictal mapping with neurovascular coupling biomarkers by structured factorization of epileptic EEG and fMRI data.

Neuroimage 2021 03 24;228:117652. Epub 2020 Dec 24.

Circuits and Systems Group (CAS), Department of Microelectronics, Delft University of Technology, Delft, the Netherlands.

EEG-correlated fMRI analysis is widely used to detect regional BOLD fluctuations that are synchronized to interictal epileptic discharges, which can provide evidence for localizing the ictal onset zone. However, the typical, asymmetrical and mass-univariate approach cannot capture the inherent, higher order structure in the EEG data, nor multivariate relations in the fMRI data, and it is nontrivial to accurately handle varying neurovascular coupling over patients and brain regions. We aim to overcome these drawbacks in a data-driven manner by means of a novel structured matrix-tensor factorization: the single-subject EEG data (represented as a third-order spectrogram tensor) and fMRI data (represented as a spatiotemporal BOLD signal matrix) are jointly decomposed into a superposition of several sources, characterized by space-time-frequency profiles. In the shared temporal mode, Toeplitz-structured factors account for a spatially specific, neurovascular 'bridge' between the EEG and fMRI temporal fluctuations, capturing the hemodynamic response's variability over brain regions. By analyzing interictal data from twelve patients, we show that the extracted source signatures provide a sensitive localization of the ictal onset zone (10/12). Moreover, complementary parts of the IOZ can be uncovered by inspecting those regions with the most deviant neurovascular coupling, as quantified by two entropy-like metrics of the hemodynamic response function waveforms (9/12). Hence, this multivariate, multimodal factorization provides two useful sets of EEG-fMRI biomarkers, which can assist the presurgical evaluation of epilepsy. We make all code required to perform the computations available at https://github.com/svaneynd/structured-cmtf.
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http://dx.doi.org/10.1016/j.neuroimage.2020.117652DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7903163PMC
March 2021

Common and distinct neural representations of aversive somatic and visceral stimulation in healthy individuals.

Nat Commun 2020 11 23;11(1):5939. Epub 2020 Nov 23.

Cognitive and Affective Neuroscience Lab, Department of Psychological and Brain Sciences, Dartmouth College, Hanover, NH, USA.

Different pain types may be encoded in different brain circuits. Here, we examine similarities and differences in brain processing of visceral and somatic pain. We analyze data from seven fMRI studies (N = 165) and five types of pain and discomfort (esophageal, gastric, and rectal distension, cutaneous thermal stimulation, and vulvar pressure) to establish and validate generalizable pain representations. We first evaluate an established multivariate brain measure, the Neurologic Pain Signature (NPS), as a common nociceptive pain system across pain types. Then, we develop a multivariate classifier to distinguish visceral from somatic pain. The NPS responds robustly in 98% of participants across pain types, correlates with perceived intensity of visceral pain and discomfort, and shows specificity to pain when compared with cognitive and affective conditions from twelve additional studies (N = 180). Pre-defined signatures for non-pain negative affect do not respond to visceral pain. The visceral versus the somatic classifier reliably distinguishes somatic (thermal) from visceral (rectal) stimulation in both cross-validation and independent cohorts. Other pain types reflect mixtures of somatic and visceral patterns. These results validate the NPS as measuring a common core nociceptive pain system across pain types, and provide a new classifier for visceral versus somatic pain.
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http://dx.doi.org/10.1038/s41467-020-19688-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7684294PMC
November 2020

Age-related GABAergic differences in the primary sensorimotor cortex: A multimodal approach combining PET, MRS and TMS.

Neuroimage 2021 02 10;226:117536. Epub 2020 Nov 10.

Department of Movement Sciences, Movement Control & Neuroplasticity Research Group, Group Biomedical Sciences, KU Leuven, Heverlee, Belgium; KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium.

Healthy aging is associated with mechanistic changes in gamma-aminobutyric acid (GABA), the most abundant inhibitory neurotransmitter in the human brain. While previous work mainly focused on magnetic resonance spectroscopy (MRS)-based GABA+ levels and transcranial magnetic stimulation (TMS)-based GABA receptor (GABAR) activity in the primary sensorimotor (SM1) cortex, the aim of the current study was to identify age-related differences in positron emission tomography (PET)-based GABAR availability and its relationship with GABA+ levels (i.e. GABA with the contribution of macromolecules) and GABAR activity. For this purpose, fifteen young (aged 20-28 years) and fifteen older (aged 65-80 years) participants were recruited. PET and MRS images were acquired using simultaneous time-of-flight PET/MR to evaluate age-related differences in GABAR availability (distribution volume ratio with pons as reference region) and GABA+ levels. TMS was applied to identify age-related differences in GABAR activity by measuring short-interval intracortical inhibition (SICI). Whereas GABAR availability was significantly higher in the SM cortex of older as compared to young adults (18.5%), there were neither age-related differences in GABA+ levels nor SICI. A correlation analysis revealed no significant associations between GABAR availability, GABAR activity and GABA+ levels. Although the exact mechanisms need to be further elucidated, it is possible that a higher GABAR availability in older adults is a compensatory mechanism to ensure optimal inhibitory functionality during the aging process.
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http://dx.doi.org/10.1016/j.neuroimage.2020.117536DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894275PMC
February 2021

Frequency-dependent functional connectivity in resting state networks.

Hum Brain Mapp 2020 Dec 25;41(18):5187-5198. Epub 2020 Aug 25.

Research Center for Motor Control and Neuroplasticity, KU Leuven, Leuven, Belgium.

Functional magnetic resonance imaging studies have documented the resting human brain to be functionally organized in multiple large-scale networks, called resting-state networks (RSNs). Other brain imaging techniques, such as electroencephalography (EEG) and magnetoencephalography (MEG), have been used for investigating the electrophysiological basis of RSNs. To date, it is largely unclear how neural oscillations measured with EEG and MEG are related to functional connectivity in the resting state. In addition, it remains to be elucidated whether and how the observed neural oscillations are related to the spatial distribution of the network nodes over the cortex. To address these questions, we examined frequency-dependent functional connectivity between the main nodes of several RSNs, spanning large part of the cortex. We estimated connectivity using band-limited power correlations from high-density EEG data collected in healthy participants. We observed that functional interactions within RSNs are characterized by a specific combination of neuronal oscillations in the alpha (8-13 Hz), beta (13-30 Hz), and gamma (30-80 Hz) bands, which highly depend on the position of the network nodes. This finding may contribute to a better understanding of the mechanisms through which neural oscillations support functional connectivity in the brain.
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http://dx.doi.org/10.1002/hbm.25184DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7670639PMC
December 2020

Resting state functional connectivity of the pain matrix and default mode network in irritable bowel syndrome: a graph theoretical analysis.

Sci Rep 2020 07 3;10(1):11015. Epub 2020 Jul 3.

Behavioral Medicine, Graduate School of Medicine, Tohoku University, Sendai, Japan.

Irritable bowel syndrome (IBS) is a functional disorder of brain-gut interactions. Differential brain responses to rectal distention between IBS and healthy controls (HCs) have been demonstrated, particularly in the pain matrix and the default mode network. This study aims to compare resting-state functional properties of these networks between IBS patients and HCs using graph analysis in two independent cohorts. We used a weighted graph analysis of the adjacency matrix based on partial correlations between time series in the different regions in each subject to determine subject specific graph measures. These graph measures were normalized by values obtained in equivalent random networks. We did not find any significant differences between IBS patients and controls in global normalized graph measures, hubs, or modularity structure of the pain matrix and the DMN in any of our two independent cohorts. Furthermore, we did not find consistent associations between these global network measures and IBS symptom severity or GI-specific anxiety but we found a significant difference in the relationship between measures of psychological distress (anxiety and/or depressive symptoms) and normalized characteristic path length. The responses of these networks to visceral stimulation rather than their organisation at rest may be primarily disturbed in IBS.
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http://dx.doi.org/10.1038/s41598-020-67048-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7335204PMC
July 2020

Network level characteristics in the emotion recognition network after unilateral temporal lobe surgery.

Eur J Neurosci 2020 09 2;52(5):3470-3484. Epub 2020 Jul 2.

Department of Neurosciences, Neuropsychiatry, Leuven Brain Institute, KU Leuven, Leuven, Belgium.

The human amygdala is considered a key region for successful emotion recognition. We recently reported that temporal lobe surgery (TLS), including resection of the amygdala, does not affect emotion recognition performance (Journal of Neuroscience, 2018, 38, 9263). In the present study, we investigate the neural basis of this preserved function at the network level. We use generalized psychophysiological interaction and graph theory indices to investigate network level characteristics of the emotion recognition network in TLS patients and healthy controls. Based on conflicting emotion processing theories, we anticipated two possible outcomes: a substantial increase of the non-amygdalar connections of the emotion recognition network to compensate functionally for the loss of the amygdala, in line with basic emotion theory versus only minor changes in network level properties as predicted by psychological construction theory. We defined the emotion recognition network in the total sample and investigated group differences on five network level indices (i.e. characteristic path length, global efficiency, clustering coefficient, local efficiency and small-worldness). The results did not reveal a significant increase in the left or right temporal lobectomy group (compared to the control group) in any of the graph measures, indicating that preserved behavioural emotion recognition in TLS is not associated with a massive connectivity increase between non-amygdalar nodes at network level. We conclude that the emotion recognition network is robust and functionally able to compensate for structural damage without substantial global reorganization, in line with a psychological construction theory.
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http://dx.doi.org/10.1111/ejn.14849DOI Listing
September 2020

Reproducibility of graph measures at the subject level using resting-state fMRI.

Brain Behav 2020 08 2;10(8):2336-2351. Epub 2020 Jul 2.

Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, Leuven, Belgium.

Introduction: Graph metrics have been proposed as potential biomarkers for diagnosis in clinical work. However, before it can be applied in a clinical setting, their reproducibility should be evaluated.

Methods: This study systematically investigated the effect of two denoising pipelines and different whole-brain network constructions on reproducibility of subject-specific graph measures. We used the multi-session fMRI dataset from the Brain Genomics Superstruct Project consisting of 69 healthy young adults.

Results: In binary networks, the test-retest variability for global measures was large at low density irrespective of the denoising strategy or the type of correlation. Weighted networks showed very low test-retest values (and thus a good reproducibility) for global graph measures irrespective of the strategy used. Comparing the test-retest values for different strategies, there were significant main effects of the type of correlation (Pearson correlation vs. partial correlation), the (partial) correlation value (absolute vs. positive vs. negative), and weight calculation (based on the raw (partial) correlation values vs. based on transformed Z-values). There was also a significant interaction effect between type of correlation and weight calculation. Similarly as for the binary networks, there was no main effect of the denoising pipeline.

Conclusion: Our results demonstrated that normalized global graph measures based on a weighted network using the absolute (partial) correlation as weight were reproducible. The denoising pipeline and the granularity of the whole-brain parcellation used to define the nodes were not critical for the reproducibility of normalized graph measures.
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http://dx.doi.org/10.1002/brb3.1705DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7428495PMC
August 2020

Use of Multimodal Imaging and Clinical Biomarkers in Presymptomatic Carriers of C9orf72 Repeat Expansion.

JAMA Neurol 2020 08;77(8):1008-1017

KU Leuven, Department of Neurosciences, Experimental Neurology, B-3000 Leuven, Belgium.

Importance: During a time with the potential for novel treatment strategies, early detection of disease manifestations at an individual level in presymptomatic carriers of a hexanucleotide repeat expansion in the C9orf72 gene (preSxC9) is becoming increasingly relevant.

Objectives: To evaluate changes in glucose metabolism before symptom onset of amyotrophic lateral sclerosis or frontotemporal dementia in preSxC9 using simultaneous fluorine 18-labeled fluorodeoxyglucose ([18F]FDG positron emission tomographic (PET) and magnetic resonance imaging as well as the mutation's association with clinical and fluid biomarkers.

Design, Setting, And Participants: A prospective, case-control study enrolled 46 participants from November 30, 2015, until December 11, 2018. The study was conducted at the neuromuscular reference center of the University Hospitals Leuven, Leuven, Belgium.

Main Outcomes And Measures: Neuroimaging data were spatially normalized and analyzed at the voxel level at a height threshold of P < .001, cluster-level familywise error-corrected threshold of P < .05, and statistical significance was set at P < .05 for the volume-of-interest level analysis, using Benjamini-Hochberg correction for multiple correction. W-score maps were computed using the individuals serving as controls as a reference to quantify the degree of [18F]FDG PET abnormality. The threshold for abnormality on the W-score maps was designated as an absolute W-score greater than or equal to 1.96. Neurofilament levels and performance on cognitive and neurologic examinations were determined. All hypothesis tests were 1-sided.

Results: Of the 42 included participants, there were 17 with the preSxC9 mutation (12 women [71%]; mean [SD] age, 51 [9] years) and 25 healthy controls (12 women [48%]; mean [SD] age, 47 [10] years). Compared with control participants, significant clusters of relative hypometabolism were found in frontotemporal regions, basal ganglia, and thalami of preSxC9 participants and relative hypermetabolism in the peri-Rolandic region, superior frontal gyrus, and precuneus cortex. W-score frequency maps revealed reduced glucose metabolism with local maxima in the insular cortices, central opercular cortex, and thalami in up to 82% of preSxC9 participants and increased glucose metabolism in the precentral gyrus and precuneus cortex in up to 71% of preSxC9 participants. Other findings in the preSxC9 group were upper motor neuron involvement in 10 participants (59%), cognitive abnormalities in 5 participants (29%), and elevated neurofilament levels in 3 of 16 individuals (19%) who underwent lumbar puncture.

Conclusions And Relevance: The results suggest that [18F]FDG PET can identify glucose metabolic changes in preSxC9 at an individual level, preceding significantly elevated neurofilament levels and onset of symptoms.
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http://dx.doi.org/10.1001/jamaneurol.2020.1087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7417970PMC
August 2020

Representation of associative and affective semantic similarity of abstract words in the lateral temporal perisylvian language regions.

Neuroimage 2020 08 1;217:116892. Epub 2020 May 1.

Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, Belgium; Neurology Department, University Hospitals Leuven, Leuven, Belgium. Electronic address:

The examination of semantic cognition has traditionally identified word concreteness as well as valence as two of the principal dimensions in the representation of conceptual knowledge. More recently, corpus-based vector space models as well as graph-theoretical analysis of large-scale task-related behavioural responses have revolutionized our insight into how the meaning of words is structured. In this fMRI study, we apply representational similarity analysis to investigate the conceptual representation of abstract words. Brain activity patterns were related to a cued-association based graph as well as to a vector-based co-occurrence model of word meaning. Twenty-six subjects (19 females and 7 males) performed an overt repetition task during fMRI. First, we performed a searchlight classification procedure to identify regions where activity is discriminable between abstract and concrete words. These regions were left inferior frontal gyrus, the upper and lower bank of the superior temporal sulcus bilaterally, posterior middle temporal gyrus and left fusiform gyrus. Representational Similarity Analysis demonstrated that for abstract words, the similarity of activity patterns in the cortex surrounding the superior temporal sulcus bilaterally and in the left anterior superior temporal gyrus reflects the similarity in word meaning. These effects were strongest for semantic similarity derived from the cued association-based graph and for affective similarity derived from either of the two models. The latter effect was mainly driven by positive valence words. This research highlights the close neurobiological link between the information structure of abstract and affective word content and the similarity in activity pattern in the lateral and anterior temporal language system.
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http://dx.doi.org/10.1016/j.neuroimage.2020.116892DOI Listing
August 2020

Different Mismatch Concepts for Magnetic Resonance Imaging-Guided Thrombolysis in Unknown Onset Stroke.

Ann Neurol 2020 06 20;87(6):931-938. Epub 2020 Apr 20.

Department of Neurology, University Hospitals Leuven, Leuven, Belgium.

Objective: To explore the prevalence of the perfusion-weighted imaging (PWI)-diffusion-weighted imaging (DWI) mismatch and response to intravenous thrombolysis in the WAKE-UP trial.

Methods: We performed a prespecified post hoc analysis of ischemic stroke patients screened for DWI-fluid-attenuated inversion recovery (FLAIR) mismatch in WAKE-UP who underwent PWI. We defined PWI-DWI mismatch as ischemic core volume < 70ml, mismatch volume > 10ml, and mismatch ratio > 1.2. Primary efficacy end point was a modified Rankin Scale score of 0-1 at 90 days, adjusted for age and symptom severity.

Results: Of 1,362 magnetic resonance imaging-screened patients, 431 underwent PWI. Of these, 57 (13%) had a double mismatch, 151 (35%) only a DWI-FLAIR mismatch, and 54 (13%) only a PWI-DWI mismatch. DWI-FLAIR mismatch was more prevalent than PWI-DWI mismatch (48%, 95% confidence interval [CI] = 43-53% vs 26%, 95% CI = 22-30%; p < 0.0001). Screening for either one of the mismatch profiles resulted in a yield of 61% (95% CI = 56-65%). Prevalence of PWI-DWI mismatch was similar in patients with (27%) or without (24%) DWI-FLAIR mismatch (p = 0.52). In an exploratory analysis in the small subgroup of 208 randomized patients with PWI, PWI-DWI mismatch status did not modify the treatment response (p for interaction = 0.73).

Interpretation: Evaluating both the DWI-FLAIR and PWI-DWI mismatch patterns in patients with unknown time of stroke onset will result in the highest yield of thrombolysis treatment. The treatment benefit of alteplase in patients with a DWI-FLAIR mismatch seems to be driven not merely by the presence of a PWI-DWI mismatch, although this analysis was underpowered. ANN NEUROL 2020;87:931-938.
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http://dx.doi.org/10.1002/ana.25730DOI Listing
June 2020

Imaging Brain Mechanisms of Functional Somatic Syndromes: Potential as a Biomarker?

Tohoku J Exp Med 2020 03;250(3):137-152

Behavioral Medicine, Tohoku University Graduate School of Medicine.

When patients present with persistent bodily complaints that cannot be explained by a symptom-linked organic pathology (medically unexplained symptoms), they are diagnosed with 'functional' somatic syndromes (FSS). Despite their prevalence, the management of FSS is notoriously challenging in clinical practice. This may be because FSS are heterogeneous disorders in terms of etiopathogenesis. They include patients with primarily peripheral dysfunction, primarily centrally driven somatic symptoms, and a mix of both. Brain-imaging studies, particularly data-driven pattern recognition methods using machine learning algorithms, could provide brain-based biomarkers for these clinical conditions. In this review, we provide an overview of our brain imaging data on brain-body interactions in one of the most well-known FSS, irritable bowel syndrome (IBS), and discuss the possible development of a brain-based biomarker for FSS. Anticipation of unpredictable pain, which commonly elicits fear in FSS patients, induced increased activity in brain areas associated with hypervigilance during rectal distention and non-distention conditions in IBS. This was coupled with dysfunctional inhibitory influence of the medial prefrontal cortex (mPFC) and pregenual anterior cingulate cortex (pACC) on stress regulation systems, resulting in the activated autonomic nervous system (ANS) and neuroendocrine system stimulated by corticotropin-releasing hormone (CRH). IBS subjects with higher alexithymia, a risk factor for FSS, showed stronger activity in the insula during rectal distention but reduced subjective sensitivity. Reduced top-down regulation of the ANS and CRH system by mPFC and pACC, discordance between the insula response to stimulation and subjective sensation of pain, and stronger threat responses in hypervigilance-related areas may be a candidate brain-based biomarker.
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http://dx.doi.org/10.1620/tjem.250.137DOI Listing
March 2020

Quantitative 18F-FDG PET-CT scan characteristics correlate with tuberculosis treatment response.

EJNMMI Res 2020 Feb 10;10(1). Epub 2020 Feb 10.

Department of Science and Technology/National Research Foundation, Centre of Excellence for Biomedical Tuberculosis Research and South African Medical Research Council Centre for Tuberculosis Research, Cape Town, South Africa.

Background: There is a growing interest in the use of F-18 FDG PET-CT to monitor tuberculosis (TB) treatment response. Tuberculosis lung lesions are often complex and diffuse, with dynamic changes during treatment and persisting metabolic activity after apparent clinical cure. This poses a challenge in quantifying scan-based markers of burden of disease and disease activity. We used semi-automated, whole lung quantification of lung lesions to analyse serial FDG PET-CT scans from the Catalysis TB Treatment Response Cohort to identify characteristics that best correlated with clinical and microbiological outcomes.

Results: Quantified scan metrics were already associated with clinical outcomes at diagnosis and 1 month after treatment, with further improved accuracy to differentiate clinical outcomes after standard treatment duration (month 6). A high cavity volume showed the strongest association with a risk of treatment failure (AUC 0.81 to predict failure at diagnosis), while a suboptimal reduction of the total glycolytic activity in lung lesions during treatment had the strongest association with recurrent disease (AUC 0.8 to predict pooled unfavourable outcomes). During the first year after TB treatment lesion burden reduced; but for many patients, there were continued dynamic changes of individual lesions.

Conclusions: Quantification of FDG PET-CT images better characterised TB treatment outcomes than qualitative scan patterns and robustly measured the burden of disease. In future, validated metrics may be used to stratify patients and help evaluate the effectiveness of TB treatment modalities.
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http://dx.doi.org/10.1186/s13550-020-0591-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7010890PMC
February 2020

CHIT1 at Diagnosis Reflects Long-Term Multiple Sclerosis Disease Activity.

Ann Neurol 2020 04 8;87(4):633-645. Epub 2020 Feb 8.

KU Leuven - Department of Neurosciences, Laboratory for Neuroimmunology, Leuven, Belgium.

Objective: Evidence for a role of microglia in the pathogenesis of multiple sclerosis (MS) is growing. We investigated association of microglial markers at time of diagnostic lumbar puncture (LP) with different aspects of disease activity (relapses, disability, magnetic resonance imaging parameters) up to 6 years later in a cohort of 143 patients.

Methods: In cerebrospinal fluid (CSF), we measured 3 macrophage and microglia-related proteins, chitotriosidase (CHIT1), chitinase-3-like protein 1 (CHI3L1 or YKL-40), and soluble triggering receptor expressed on myeloid cells 2 (sTREM2), as well as a marker of neuronal damage, neurofilament light chain (NfL), using enzyme-linked immunosorbent assay and electrochemiluminescence. We investigated the same microglia-related markers in publicly available RNA expression data from postmortem brain tissue.

Results: CHIT1 levels at diagnostic LP correlated with 2 aspects of long-term disease activity after correction for multiple testing. First, CHIT1 increased with reduced tissue integrity in lesions at a median 3 years later (p = 9.6E-04). Second, CHIT1 reflected disease severity at a median 5 years later (p = 1.2E-04). Together with known clinical covariates, CHIT1 levels explained 12% and 27% of variance in these 2 measures, respectively, and were able to distinguish slow and fast disability progression (area under the curve = 85%). CHIT1 was the best discriminator of chronic active versus chronic inactive lesions and the only marker correlated with NfL (r = 0.3, p = 0.0019). Associations with disease activity were, however, independent of NfL.

Interpretation: CHIT1 CSF levels measured during the diagnostic LP reflect microglial activation early on in MS and can be considered a valuable prognostic biomarker for future disease activity. ANN NEUROL 2020;87:633-645.
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http://dx.doi.org/10.1002/ana.25691DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7187166PMC
April 2020

Automated speech analysis to improve TMS-based language mapping: Algorithm and proof of concept.

Brain Stimul 2020 Jan - Feb;13(1):267-269. Epub 2019 Oct 11.

Laboratory for Epilepsy Research, Department of Neurosciences, KU Leuven, Herestraat 49 Box 7003, 3000 Leuven, Belgium; Department of Neurology, UZ Leuven, Belgium.

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http://dx.doi.org/10.1016/j.brs.2019.10.001DOI Listing
October 2019

Insula Activity to Visceral Stimulation and Endocrine Stress Responses as Associated With Alexithymia in Patients With Irritable Bowel Syndrome.

Psychosom Med 2020 01;82(1):29-38

From the Frontier Research Institute for Interdisciplinary Sciences (Kano) and Behavioral Medicine, Graduate School of Medicine (Kano, Muratsubaki, Yagihashi, Morishita, Kanazawa, Fukudo), Tohoku University; Diagnostic Radiology (Mugikura, Takase), Tohoku University Hospital, Sendai, Japan; Laboratories for Cognitive Neurology (Dupont) and Brain-Gut Axis Studies, Translational Research Center for Gastrointestinal Disorders (Van Oudenhove), KU Leuven, Leuven, Belgium.

Objective: Few studies have investigated associations between alexithymia and physiological mechanisms in psychosomatic diseases. We examined associations between alexithymia and 1) perception and brain processing of visceral stimulation and 2) the endocrine responses to corticotrophin-releasing hormone (CRH) in healthy individuals and patients with irritable bowel syndrome (IBS).

Methods: The study included 29 patients with IBS and 35 age- and sex-matched healthy controls (HCs). Alexithymia was measured using the 20-item Toronto Alexithymia Scale (TAS-20). Brain responses to rectal distention and its anticipation were measured by functional magnetic resonance imaging and analyzed at a voxel-level threshold of puncorrected < .001 combined with a cluster-level threshold of pFWE-corrected < .05. On a different day, plasma adrenocorticotropic hormone and cortisol responses after intravenous CRH administration were measured.

Results: TAS-20 scores did not differ significantly between patients with IBS and HCs (p = .18). TAS-20 scores correlated positively with the individual rectal discomfort thresholds (βrobust = 0.49, p = .03) and negatively with the rating of fear before rectal distention (βrobust = -1.63, p = .04) in patients with IBS but not in HCs. Brain responses to rectal distention in the right insula and other brain regions were positively associated with TAS-20 scores to a greater extent in patients with IBS than in HCs. Individuals with higher TAS-20 scores (both patients with IBS and HCs) demonstrated stronger adrenocorticotropic hormone responses to CRH administration (F(4,224) = 3.54, p = .008).

Conclusion: Higher alexithymia scores are associated with stronger physiological responses, but lower anticipatory fear ratings and higher discomfort thresholds, particularly in patients with IBS.
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http://dx.doi.org/10.1097/PSY.0000000000000729DOI Listing
January 2020

Early prediction of donepezil cognitive response in Alzheimer's disease by brain perfusion single photon emission tomography.

Brain Imaging Behav 2019 Dec;13(6):1665-1673

Department of Psychiatry, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.

Currently, there is no effective means to evaluate donepezil response. We evaluated brain perfusion change at 4 h after donepezil administration (4 h DNPZ) to predict cognitive responses after 6 months of medication. CERAD neuropsychological assessment battery was used to define cognitive response at 6 months. We compared 4 h DNPZ to baseline single photon emission tomography (SPECT) by statistical parametric mapping to identify perfusion changes in responders (N = 16) and non-responders (N = 7). In responders, there were significant relatively increase in perfusion in left parietal lobe (BA39, 7, 1), right superior frontal gyrus (BA6) and right middle occipital gyrus (BA39). In the non-responders, perfusion was relatively increase in the left parietal lobe (BA39) only. In an explorative analysis, we found a significant correlation between perfusion changes in right BA6 and CERAD score changes at 6 months. Different SPECT perfusion changes at 4 h after donepezil administration were demonstrated in the group of responders and non-responders with potential correlation with CERAD score change. Thus, 4 h DNPZ brain perfusion SPECT can be used to predict donepezil response at 6 months.
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http://dx.doi.org/10.1007/s11682-019-00182-9DOI Listing
December 2019

Semi-automated EEG Enhancement Improves Localization of Ictal Onset Zone With EEG-Correlated fMRI.

Front Neurol 2019 2;10:805. Epub 2019 Aug 2.

Department of Electrical Engineering (ESAT), STADIUS Center for Dynamical Systems, Signal Processing and Data Analytics, Leuven, Belgium.

To improve the accuracy of detecting the ictal onset zone, we propose to enhance the epilepsy-related activity present in the EEG signals, before mapping their BOLD correlates through EEG-correlated fMRI analysis. Based solely on a segmentation of interictal epileptic discharges (IEDs) on the EEG, we train multi-channel Wiener filters (MWF) which enhance IED-like waveforms, and suppress background activity and noisy influences. Subsequently, we use EEG-correlated fMRI to find the brain regions in which the BOLD signal fluctuation corresponds to the filtered signals' time-varying power (after convolving with the hemodynamic response function), and validate the identified regions by quantitatively comparing them to ground-truth maps of the (resected or hypothesized) ictal onset zone. We validate the performance of this novel predictor vs. that of commonly used unitary or power-weighted predictors and a recently introduced connectivity-based metric, on a cohort of 12 patients with refractory epilepsy. The novel predictor, derived from the filtered EEG signals, allowed the detection of the ictal onset zone in a larger percentage of epileptic patients (92% vs. at most 83% for the other predictors), and with higher statistical significance, compared to existing predictors. At the same time, the new method maintains maximal specificity by not producing false positive activations in healthy controls. The findings of this study advocate for the use of the MWF to maximize the signal-to-noise ratio of IED-like events in the interictal EEG, and subsequently use time-varying power as a sensitive predictor of the BOLD signal, to localize the ictal onset zone.
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http://dx.doi.org/10.3389/fneur.2019.00805DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6688528PMC
August 2019

Long-term impact of prenatal exposure to chemotherapy on executive functioning: An ERP study.

Clin Neurophysiol 2019 09 9;130(9):1655-1664. Epub 2019 Jul 9.

Department of Development and Regeneration, KU Leuven, Leuven, Belgium; Department of Pediatrics, University Hospitals Leuven, Leuven, Belgium.

Objective: This study examines the long-term impact of prenatal exposure to chemotherapy on executive functioning and the contribution of late-prematurity to this effect, using event-related potentials.

Methods: Mothers of the prenatal-exposed children (n = 20) were diagnosed with cancer and received chemotherapeutic treatment during pregnancy. We recruited healthy controls (n = 20) who were matched on a 1:1 ratio regarding prematurity, age and sex. We assessed executive functioning at the age of nine, using two event-related potential paradigms: a Go/Nogo paradigm to investigate processes of response inhibition and conflict monitoring, as well as a Posner paradigm to investigate spatial attention.

Results: Lower potentials were found in prenatal-exposed children compared to controls in the Go/Nogo P3 and Posner positive slow wave. Moreover, prenatal-exposed children responded slower on the Posner paradigm compared to controls (p < .033), with more incorrect responses (p = .023). In the control group, the N2 Go/Nogo wave was more pronounced in children born after a longer gestation.

Conclusions: This is the first study that demonstrates an effect of prenatal exposure to chemotherapy on the development of executive functioning, not limited to the effect of late-prematurity.

Significance: This study emphasizes the necessity of a long-term follow-up of prenatal-exposed children to re-inform clinical practice on the costs and benefits of late-premature induction over treatment during pregnancy.
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http://dx.doi.org/10.1016/j.clinph.2019.06.012DOI Listing
September 2019

RE: "ASSOCIATION BETWEEN REDUCTIONS OF NUMBER OF CIGARETTES SMOKED PER DAY AND MORTALITY AMONG OLDER ADULTS IN THE UNITED STATES".

Am J Epidemiol 2019 09;188(9):1756-1757

Département de pharmacologie, Hôpital Pitié-Salpêtrière-Sorbonne Université, Paris, France.

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http://dx.doi.org/10.1093/aje/kwz154DOI Listing
September 2019

Parasympathetic activity correlates with subjective and brain responses to rectal distension in healthy subjects but not in non-constipated patients with irritable bowel syndrome.

Sci Rep 2019 05 14;9(1):7358. Epub 2019 May 14.

Behavioral Medicine, Graduate School of Medicine, Tohoku University, Sendai, Japan.

The nociceptive and autonomic nervous systems (ANS) are significantly intertwined. Decoupling of these systems may occur in pathological pain conditions, including irritable bowel syndrome (IBS). We investigated ANS activity and its association with visceral perception and brain activity during rectal distention in 27 patients with non-constipated IBS and 33 controls by assessing heart rate variability (HRV) using electrocardiography at rest, before, and during colorectal distention. Brain responses to colorectal distention were measured using functional magnetic resonance imaging and correlated with individual ANS function parameters. The IBS group displayed blunted sympathovagal balance [low/high-frequency ratio (LF:HF) of HRV] in response to colorectal distention compared with controls (P = 0.003). In controls, basal parasympathetic tone (HF component of HRV) was significantly negatively correlated with toleration threshold to the rectal distention, but not in patients with IBS (group comparison P = 0.04). Further, a positive correlation between baseline HF values and neural responses to rectal distension was found in the right caudate, bilateral dorsolateral anterior cingulate cortex, and pregenual anterior cingulate cortex in the control group but not in the IBS group. The results indicate abnormal interactions between ANS activity and the brain mechanisms underlying visceral perception in patients with IBS.
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http://dx.doi.org/10.1038/s41598-019-43455-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6517375PMC
May 2019

Multimodal magnetic resonance imaging to identify stroke onset within 6 h in patients with large vessel occlusions.

Eur Stroke J 2018 Jun 1;3(2):185-192. Epub 2018 Feb 1.

Department of Neurosciences, Experimental Neurology and Leuven Research Institute for Neuroscience and Disease (LIND), KU Leuven - University of Leuven, Leuven, Belgium.

Introduction: Mechanical thrombectomy within 6 h after stroke onset improves the outcome in patients with large vessel occlusions. The aim of our study was to establish a model based on diffusion weighted and perfusion weighted imaging to provide an accurate prediction for the 6 h time-window in patients with unknown time of stroke onset.

Patients And Methods: A predictive model was designed based on data from the DEFUSE 2 study and validated in a subgroup of patients with large vessel occlusions from the AXIS 2 trial.

Results: We constructed the model in 91 patients from DEFUSE 2. The following parameters were independently associated with <6 h time-window and included in the model: interquartile range and median relative diffusion weighted imaging, hypoperfusion intensity ratio, core volume and the interaction between median relative diffusion weighted imaging and hypoperfusion intensity ratio as predictors of the 6 h time-window. The area under the curve was 0.80 with a positive predictive value of 0.90 (95%CI 0.79-0.96). In the validation cohort (N = 90), the area under the curve was 0.73 ( for difference = 0.4) with a positive predictive value of 0.85 (95%CI 0.69-0.95).

Discussion: After validation in a larger independent dataset the model can be considered to select patients for endovascular treatment in whom stroke onset is unknown.

Conclusion: In patients with large vessel occlusion and unknown time of stroke onset an automated multivariate imaging model is able to select patients who are likely within the 6 h time-window.
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http://dx.doi.org/10.1177/2396987317753486DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6460412PMC
June 2018

Left perirhinal cortex codes for semantic similarity between written words defined from cued word association.

Neuroimage 2019 05 10;191:127-139. Epub 2019 Feb 10.

Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, Belgium; Neurology Department, University Hospitals Leuven, 3000, Leuven, Belgium. Electronic address:

Knowledge of visual and nonvisual attributes of concrete entities is distributed over neocortical uni- and polymodal association cortex. Here we investigated the role of left perirhinal cortex in explicit knowledge retrieval from written words. We examined whether it extended across visual and nonvisual properties, animate and inanimate entities, how this differed from picture input and how specific it was for perirhinal cortex compared to surrounding structures. The semantic similarity between stimuli was determined on the basis of a word association-based model. Eighteen participants participated in this event-related fMRI experiment. During property verification, the left perirhinal cortex coded for the similarity in meaning between written words. No differences were found between visual and nonvisual properties or between animate and inanimate entities. Among the surrounding regions, a semantic similarity effect for written words was also present in the left parahippocampal gyrus, but not in the hippocampus nor in the right perirhinal cortex. Univariate analysis revealed higher activity for visual property verification in visual processing regions and for nonvisual property verification in an extended system encompassing the superior temporal sulcus along its anterior-posterior axis, the inferior and the superior frontal gyrus. The association strength between the concept and the property correlated positively with fMRI response amplitude in visual processing regions, and negatively with response amplitude in left inferior and superior frontal gyrus. The current findings establish that input-modality determines the semantic similarity effect in left perirhinal cortex more than the content of the knowledge retrieved or the semantic control demand do. We propose that left perirhinal cortex codes for the association between a concrete written word and the object it refers to and operates as a connector hub linking written word input to the distributed cortical representation of word meaning.
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http://dx.doi.org/10.1016/j.neuroimage.2019.02.011DOI Listing
May 2019

Quantitative Analyses Help in Choosing Between Simultaneous vs. Separate EEG and fMRI.

Front Neurosci 2018 10;12:1009. Epub 2019 Jan 10.

Laboratory for Cognitive Neurology, KU Leuven, Leuven, Belgium.

Simultaneous registration of scalp electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) is considered an attractive approach for studying brain function non-invasively. It combines the better spatial resolution of fMRI with the better temporal resolution of EEG, but comes at the cost of increased measurement artifact and the accompanying artifact preprocessing. This paper presents a study of the residual signal quality based on temporal signal to noise ratio (TSNR) for fMRI and fast Fourier transform (FFT) for EEG, after optimized conventional signal preprocessing. Measurements outside the magnetic resonance imaging scanner and inside the scanner prior to and during image acquisition were compared. For EEG, frequency and region dependent significant effects on FFT squared amplitudes were observed between separately vs. simultaneously recorded EEG and fMRI, with larger effects during image acquisition than without image acquisition inside the scanner bore. A graphical user interface was developed to aid in quality checking these measurements. For fMRI, separately recorded EEG-fMRI revealed relatively large areas with a significantly higher TSNR in right occipital and parietal regions and in the cingulum, compared to separately recorded EEG-fMRI. Simultaneously recorded EEG-fMRI showed significantly higher TSNR in inferior occipital cortex, diencephalon and brainstem, compared to separately recorded EEG-fMRI. Quantification of EEG and fMRI signals showed significant, but sometimes subtle, changes between separate compared to simultaneous EEG-fMRI measurements. To avoid interference with the experiment of interest in a simultaneous EEG-fMRI measurement, it seems warranted to perform a quantitative evaluation to ensure that there are no such uncorrectable effects present in regions or frequencies that are of special interest to the research question at hand.
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http://dx.doi.org/10.3389/fnins.2018.01009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6335318PMC
January 2019