R. Marecek

Central European Institute of Technology-Czech Republic, Brünn, South Moravian, Czech Republic

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Publications (85)277.96 Total impact

  • Daniel Joel Shaw · Radek Mareček · Milan Brázdil ·
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    ABSTRACT: Déjà vu (DV) is an eerie phenomenon experienced frequently as an aura of temporal lobe epilepsy, but also reported commonly by healthy individuals. The former pathological manifestation appears to result from aberrant neural activity among brain structures within the medial temporal lobes. Recent studies also implicate medial temporal brain structures in the non-pathological experience of DV, but as one element of a diffuse neuroanatomical correlate; it remains to be seen if neural activity among the medial temporal lobes also underlies this benign manifestation. The present study set out to investigate this. Due to its unpredictable and infrequent occurrence, however, non-pathological DV does not lend itself easily to functional neuroimaging. Instead, we draw on research showing that brain structure covaries among regions that interact frequently as nodes of functional networks. Specifically, we assessed whether grey-matter covariance among structures implicated in non-pathological DV differs according to the frequency with which the phenomenon is experienced. This revealed two diverging patterns of structural covariation: Among the first, comprised primarily of medial temporal structures and the caudate, grey-matter volume becomes more positively correlated with higher frequency of DV experience. The second pattern encompasses medial and lateral temporal structures, among which greater DV frequency is associated with more negatively correlated grey matter. Using a meta-analytic method of co-activation mapping, we demonstrate a higher probability of functional interactions among brain structures constituting the former pattern, particularly during memory-related processes. Our findings suggest that altered neural signalling within memory-related medial temporal brain structures underlies both pathological and non-pathological DV.
    Brain Imaging and Behavior 11/2015; DOI:10.1007/s11682-015-9471-8 · 4.60 Impact Factor

  • Journal of Psychophysiology 09/2015; DOI:10.1027/0269-8803/a000151 · 1.59 Impact Factor
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    ABSTRACT: Abstract: Background: Repetitive transcranial magnetic stimulation (rTMS) is a promising tool to study and modulate brain plasticity. Objective: Our aim was to investigate the effects of rTMS on cognitive functions in patients with mild cognitive impairment and Alzheimer’s disease (MCI/AD) and assess the effect of gray matter (GM) atrophy on stimulation outcomes. Methods: Twenty MCI/AD patients participated in the proof-of-concept controlled study. Each patient received three sessions of 10 Hz rTMS of the right inferior frontal gyrus (IFG), the right superior temporal gyrus (STG), and the vertex (VTX, a control stimulation site) in a randomized order. Cognitive functions were tested prior to and immediately after each session. The GM volumetric data of patients were: 1)compared to healthy controls (HC) using source-based morphometry; 2) correlated with rTMS-induced cognitive improvement. Results: The effect of the stimulated site on the difference in cognitive scores was statistically significant for the Word part of the Stroop test (ST-W, p = 0.012, linear mixed models). As compared to the VTX stimulation, patients significantly improved after both IFG and STG stimulation in this cognitive measure. MCI/AD patients had significant GM atrophy in characteristic brain regions as compared to HC (p = 0.029, Bonferroni corrected). The amount of atrophy correlated with the change in ST-W scores after rTMS of the STG. Conclusion: rTMS enhanced cognitive functions in MCI/AD patients. We demonstrated for the first time that distinct pattern of GM atrophy in MCI/AD diminishes the cognitive effects induced by rTMS of the temporal neocortex. http://content.iospress.com/download/journal-of-alzheimers-disease/jad150067?id=journal-of-alzheimers-disease%2Fjad150067
    Journal of Alzheimer's disease: JAD 08/2015; 48(1):251-260. DOI:10.3233/JAD-150067 · 4.15 Impact Factor
  • M Barton · R Marecek · I Rektor · P Filip · E Janousova · M Mikl ·
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    ABSTRACT: In some fields of fMRI data analysis, using correct methods for dealing with noise is crucial for achieving meaningful results. This paper provides a quantitative assessment of the effects of different preprocessing and noise filtering strategies on psychophysiological interactions (PPI) methods for analyzing fMRI data where noise management has not yet been established. Both real and simulated fMRI data were used to assess these effects. Four regions of interest (ROIs) were chosen for the PPI analysis on the basis of their engagement during two tasks. PPI analysis was performed for 32 different preprocessing and analysis settings, which included data filtering with RETROICOR or no such filtering; different filtering of the ROI "seed" signal with a nuisance data-driven time series; and the involvement of these data-driven time series in the subsequent PPI GLM analysis. The extent of the statistically significant results was quantified at the group level using simple descriptive statistics. Simulated data were generated to assess statistical improvement of different filtering strategies. We observed that different approaches for dealing with noise in PPI analysis yield differing results in real data. In simulated data, we found RETROICOR, seed signal filtering and the addition of data-driven covariates to the PPI design matrix significantly improves results. We recommend the use of RETROICOR, and data-driven filtering of the whole data, or alternatively, seed signal filtering with data-driven signals and the addition of data-driven covariates to the PPI design matrix. Copyright © 2015. Published by Elsevier B.V.
    Journal of Neuroscience Methods 07/2015; 253. DOI:10.1016/j.jneumeth.2015.06.021 · 2.05 Impact Factor
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    Clinical Neurophysiology 03/2015; 126(3). DOI:10.1016/j.clinph.2014.10.176 · 3.10 Impact Factor

  • Clinical Neurophysiology 03/2015; 126(3):e42-e43. DOI:10.1016/j.clinph.2014.10.195 · 3.10 Impact Factor

  • Clinical Neurophysiology 03/2015; 126(3):e47. DOI:10.1016/j.clinph.2014.10.207 · 3.10 Impact Factor
  • E. Bujnošková · J. Fousek · R. Mareček · I. Rektor ·

    Clinical Neurophysiology 03/2015; 126(3):e43. DOI:10.1016/j.clinph.2014.10.196 · 3.10 Impact Factor
  • N. Elfmarková · R. Mareček · S. Rapcsak · I. Rektorová ·

    Clinical Neurophysiology 03/2015; 126(3):e45-e46. DOI:10.1016/j.clinph.2014.10.204 · 3.10 Impact Factor

  • Clinical Neurophysiology 03/2015; 126(3):e37-e38. DOI:10.1016/j.clinph.2014.10.183 · 3.10 Impact Factor
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    ABSTRACT: Introduction: Our aim was to investigate whether grey matter atrophy as assessed by T1-weighted MR-based brain morphometry affects cognitive outcome of repetitive transcranial magnetic stimulation (rTMS) in patients with mild cognitive impairment and early Alzheimer’s disease (MCI-AD). Methods: MCI-AD patients (n=20, age 73 ± 7 years) underwent brain MRI scanning and three rTMS sessions (applied over two active stimulation sites: right superior temporal gyrus [STG], right inferior frontal gyrus [IFG] and a control site: vertex, using the frameless stereotaxy), 2250 stimuli per session at 90% of resting motor threshold. Grey matter (GM) volumes were compared between MCI-AD and gender- and age-matched healthy controls (HC: n=17, age 69 ± 7 years) using the source based morphometry method and a Mann-Whitney U test. Regions with strong inter-group differences in significant components (p<0.05, Bonferroni corrected) were visualized using: threshold set at Z˃2.5, extent threshold 100 voxels. The structural data were correlated with behavioural outcomes of the relevant stimulation sessions. Results: rTMS effects of the stimulated sites (active vs. control) on the difference in values of the Word part of Stroop test (ST-W) scores were statistically significant (p=0.012; linear mixed models), i.e. we observed an improved performance after stimulation over active sites. The patients revealed GM atrophy bilaterally in the inferior temporal gyrus, putamen and cerebellum as compared to HC (p=0.029, corrected). The component loadings correlated with the magnitude of the ST-W score changes that were induced by rTMS of the right STG, i.e. the higher the GM atrophy the lower the improvement on the ST-W after STG-rTMS. Conclusion: rTMS of the right STG and IFG led to improved attention and psychomotor speed in MCI-AD patients. We demonstrated for the first time that the brain atrophy in MCI-AD has an important impact on cognitive effects induced by rTMS applied over the temporal neocortex.
    Brain Stimulation 03/2015; 8(2):345-346. DOI:10.1016/j.brs.2015.01.117 · 4.40 Impact Factor
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    René Labounek · Martin Lamoš · Radek Mareček · Milan Brázdil · Jiří Jan ·
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    ABSTRACT: The paper deals with joint analysis of fMRI and scalp EEG data, simultaneously acquired during event-related oddball experiment. The analysis is based on deriving temporal sequences of EEG powers in individual frequency bands for the selected EEG electrodes and using them as regressors in the General Linear Model (GLM). Given the infrequent use of EEG spectral changes to explore task-related variability, we focused on the aspects of parameter setting during EEG regressor calculation and searched for such parameters that can detect task-related variability in EEG-fMRI data. We proposed a novel method that uses relative EEG power in GLM. Parameter, the type of power value, has a direct impact as to whether task-related variability is detected or not. For relative power, the final results are sensitive to the choice of frequency band of interest. The electrode selection also has certain impact; however, the impact is not crucial. It is insensitive to the choice of EEG power series temporal weighting step. Relative EEG power characterizes the experimental task activity better than the absolute power. Absolute EEG power contains broad spectrum component. Task-related relative power spectral formulas were derived. For particular set of parameters, our results are consistent with previously published papers. Our work expands current knowledge by new findings in spectral patterns of different brain processes related to the experimental task. To make analysis to be sensitive to task-related variability, the parameters type of power value and frequency band should be set properly. Copyright © 2015. Published by Elsevier B.V.
    Journal of Neuroscience Methods 02/2015; 245. DOI:10.1016/j.jneumeth.2015.02.016 · 2.05 Impact Factor
  • Lenka Krajcovicova · Radek Marecek · Michal Mikl · Irena Rektorova ·
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    ABSTRACT: The resting brain exhibits continuous intrinsic activity, which is correlated between groups of regions forming resting state networks. Evaluating resting connectivity is a popular approach for studying brain diseases. Several hundred studies are now available that address integrity of resting connectivity in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI), as well as preclinical at-risk subjects. Most studies focus on the default mode network, a system of specific brain areas showing strong connected resting activity that attenuates during goal-directed behavior. The extent of intrinsic brain activity tends to be strongly correlated with cognitive processes and is specifically disrupted in AD and MCI patients and at-risk subjects, with changes seeming to evolve during the transition between the disease stages. In this study, we review the current findings in default mode network and other resting state network studies in AD and MCI patients and at-risk subjects as assessed by resting state functional magnetic resonance imaging.
    Current Neurology and Neuroscience Reports 10/2014; 14(10):491. DOI:10.1007/s11910-014-0491-3 · 3.06 Impact Factor
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    ABSTRACT: Introduction: Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive tool for modulating cortical activity. Objectives: In this pilot study, we evaluated the effects of high frequency rTMS applied over the right inferior frontal gyrus (IFG) on cognitive functions in patients with amnestic mild cognitive impairment (MCI) or incipient dementia due to Alzheimer’s disease (AD). Methods: Ten patients (6 men; 4 women, mean age 72 ± 8 years; MMSE 23 ± 3.56) were enrolled in a randomized, placebo-controlled study with a crossover design. All participants received 3 sessions of 10 Hz rTMS over the non-dominant right hemisphere in random order: IFG (active stimulation site) and vertex (control stimulation site). Intensities were adjusted to 90% of resting motor threshold. A total of 2250 pulses were applied in a session. The Trail Making Test (TMT), the Stroop test, and the complex visual scene encoding task (CVSET) were administered before and immediately after each session. The Wilcoxon paired test was used for data analysis. Results: Stimulation applied over the IFG induced improvement in the TMT parts A (p = 0.037) and B (p = 0.049). No significant changes were found in the Stroop test or the CVSET after the IFG stimulation. We observed no significant cognitive aftereffects of rTMS applied over the vertex. Conclusions: High frequency rTMS of the right IFG induced significant improvement of attention and psychomotor speed in patients with MCI/mild dementia due to AD. This pilot study is part of a more complex protocol and ongoing research.
    Journal of the Neurological Sciences 08/2014; 346(1-2). DOI:10.1016/j.jns.2014.08.036 · 2.47 Impact Factor
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    ABSTRACT: Background: The default mode network (DMN) decreases its activity when switching from a resting state to a cognitive task condition, while activity of the network engaged in the given task increases. Visual processing is typically disturbed in Parkinson's disease dementia (PDD). Objective: Using functional MRI, we studied the DMN effective connectivity patterns in PDD as compared with cognitively normal patients with Parkinson's disease (PD) and healthy controls (HC) when switching from baseline to a visual cognitive task condition. Methods: In all, 14 PDD, 18 PD, and 18 age-matched healthy controls participated in this functional MRI study. We used a psychophysiological interaction analysis with the precuneus (PCu) as a seed. The threshold was set at p(FWE) <0.05. Results: The healthy controls showed greater PCu connectivity with the bilateral middle temporal/middle occipital gyri at baseline than during the task condition. The correlation direction changed from positive to negative. Both PD and PDD showed disturbed DMN connectivity with the brain regions that are involved in bottom-up visual processing. In PD, we also found impaired integration of the areas engaged in the ventral attentional network, which might reflect specific attentional deficits observed during the early course of PD. In mild PDD, we detected increased engagement of areas involved in the dorsal attentional network, which corresponds to increased top-down control in this patient group as compared to the healthy controls. Conclusion: Our results show impaired dynamic interplay between large scale brain networks in PD that spread far beyond the motor system.
    Journal of Alzheimer's disease: JAD 08/2014; 42. DOI:10.3233/JAD-132684 · 4.15 Impact Factor
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    ABSTRACT: A clear concept of epileptic zones remains of high clinical relevance in presurgical evaluation of refractory epilepsy patients and in resection planning. Recent advances in understanding how each of the epileptic zones is functionally organized strengthened the importance of the network concept. It has been shown that neuronal networks underlying the individual epileptic zone may involve multiple brain structures with complex interactions between them. The network concept has impact not only for better understanding of pathophysiology of partial epilepsy but also for clinical practice, particularly for epilepsy surgery. This review examines recent reports on the use of advanced imaging techniques which enable to map the epileptic zones and their structural and functional organization. Magnetic resonance postprocessing substantially improved the accuracy in detection of the epileptogenic lesions. The seizure-onset zone is primarily determined by electrophysiology but can also be localized using single photon emission computed tomography. The functional deficit zone is commonly assessed by a number of tests including methods of functional neuroimaging (positron emission tomography) which can delineate hypometabolic cortical areas and subcortical structures. Hemodynamic fluctuations associated with interictal epileptiform discharges can be detected by novel functional magnetic resonance technique which is nowadays widely used for the irritative zone localization. These techniques open new prospect for epilepsy surgery in patients who were previously considered as not suitable candidates of surgical treatment.
    International Review of Neurobiology 08/2014; 114C:245-278. DOI:10.1016/B978-0-12-418693-4.00010-8 · 1.92 Impact Factor

  • Clinical Neurophysiology; 06/2014
  • I. Rektor · R. Kuba · M. Brazdil · R. Marecek · J. Chrastina · I. Rektorova · M. Mikl ·

    Clinical Neurophysiology 06/2014; 125:S258. DOI:10.1016/S1388-2457(14)50843-7 · 3.10 Impact Factor
  • I. Rektorova · L. Krajcovicova · R. Marecek · M. Mikl ·

    Clinical Neurophysiology 06/2014; 125:S126-S127. DOI:10.1016/S1388-2457(14)50413-0 · 3.10 Impact Factor
  • Lenka Krajcovicova · Michal Mikl · Radek Marecek · Irena Rektorova ·
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    ABSTRACT: Changes in connectivity of the posterior node of the default mode network (DMN) were studied when switching from baseline to a cognitive task using functional magnetic resonance imaging. In all, 15 patients with mild to moderate Alzheimer's disease (AD) and 18 age-, gender-, and education-matched healthy controls (HC) participated in the study. Psychophysiological interactions analysis was used to assess the specific alterations in the DMN connectivity (deactivation-based) due to psychological effects from the complex visual scene encoding task. In HC, we observed task-induced connectivity decreases between the posterior cingulate and middle temporal and occipital visual cortices. These findings imply successful involvement of the ventral visual pathway during the visual processing in our HC cohort. In AD, involvement of the areas engaged in the ventral visual pathway was observed only in a small volume of the right middle temporal gyrus. Additional connectivity changes (decreases) in AD were present between the posterior cingulate and superior temporal gyrus when switching from baseline to task condition. These changes are probably related to both disturbed visual processing and the DMN connectivity in AD and reflect deficits and compensatory mechanisms within the large scale brain networks in this patient population. Studying the DMN connectivity using psychophysiological interactions analysis may provide a sensitive tool for exploring early changes in AD and their dynamics during the disease progression.
    Journal of Alzheimer's disease: JAD 05/2014; 41(4). DOI:10.3233/JAD-131208 · 4.15 Impact Factor

Publication Stats

408 Citations
277.96 Total Impact Points


  • 2012-2015
    • Central European Institute of Technology-Czech Republic
      Brünn, South Moravian, Czech Republic
    • St. Ann's University Hospital Brno
      Brünn, South Moravian, Czech Republic
  • 2008-2015
    • Masaryk University
      • • Research group Molecular and Functional Neuroimaging
      • • Research group Applied Neroscience
      • • Department of Neurology
      • • I. neurologická klinika
      Brünn, South Moravian, Czech Republic
  • 2006-2010
    • St. Anne´s University Hospital
      Brünn, South Moravian, Czech Republic
  • 2007
    • Brno University of Technology
      • Faculty of Electrical Engineering and Communication
      Brünn, South Moravian, Czech Republic