TY - JOUR A1 - Fellner, Marie-Christin A1 - Volberg, Gregor A1 - Wimber, Maria A1 - Goldhacker, Markus A1 - Greenlee, Mark W. A1 - Hanslmayr, Simon T1 - Spatial mnemonic encoding: Theta power decreases and medial temporal lobe BOLD increases co-occur during the usage of the method of loci JF - eNeuro N2 - The method of loci is one, if not the most, efficient mnemonic encoding strategy. This spatial mnemonic combines the core cognitive processes commonly linked to medial temporal lobe (MTL) activity: spatial and associative memory processes. During such processes, fMRI studies consistently demonstrate MTL activity, while electrophysiological studies have emphasized the important role of theta oscillations (3–8 Hz) in the MTL. However, it is still unknown whether increases or decreases in theta power co-occur with increased BOLD signal in the MTL during memory encoding. To investigate this question, we recorded EEG and fMRI separately, while human participants used the spatial method of loci or the pegword method, a similarly associative but nonspatial mnemonic. The more effective spatial mnemonic induced a pronounced theta power decrease source localized to the left MTL compared with the nonspatial associative mnemonic strategy. This effect was mirrored by BOLD signal increases in the MTL. Successful encoding, irrespective of the strategy used, elicited decreases in left temporal theta power and increases in MTL BOLD activity. This pattern of results suggests a negative relationship between theta power and BOLD signal changes in the MTL during memory encoding and spatial processing. The findings extend the well known negative relation of alpha/beta oscillations and BOLD signals in the cortex to theta oscillations in the MTL. KW - EEG KW - fMRI KW - memory encoding KW - method of loci KW - mnemonics KW - theta oscillations Y1 - 2016 U6 - https://doi.org/10.1523/ENEURO.0184-16.2016 SN - 2373-2822 VL - 3 IS - 6 SP - 1 EP - 16 PB - Society for Neuroscience CY - Washington, DC ER - TY - JOUR A1 - Goldhacker, Markus A1 - Keck, P. A1 - Igel, A. A1 - Lang, Elmar Wolfgang A1 - Tomé, Ana Maria T1 - A multi-variate blind source separation algorithm JF - Computer Methods and Programs in Biomedicine N2 - Background and objective The study follows the proposal of decomposing a given data matrix into a product of independent spatial and temporal component matrices. A multi-variate decomposition approach is presented, based on an approximate diagonalization of a set of matrices computed using a latent space representation. Methods The proposed methodology follows an algebraic approach, which is common to space, temporal or spatiotemporal blind source separation algorithms. More specifically, the algebraic approach relies on singular value decomposition techniques, which avoids computationally costly and numerically instable matrix inversion. The method is equally applicable to correlation matrices determined from second order correlations or by considering fourth order correlations. Results The resulting algorithms are applied to fMRI data sets either to extract the underlying fMRI components or to extract connectivity maps from resting state fMRI data collected for a dynamic functional connectivity analysis. Intriguingly, our algorithm shows increased spatial specificity compared to common approaches, while temporal precision stays similar. Conclusion The study presents a novel spatiotemporal blind source separation algorithm, which is both robust and avoids parameters that are difficult to fine tune. Applied on experimental data sets, the new method yields highly confined and focused areas with least spatial extent in the retinotopy case, and similar results in the dynamic functional connectivity analyses compared to other blind source separation algorithms. Therefore, we conclude that our novel algorithm is highly competitive and yields results, which are superior or at least similar to existing approaches. KW - Blind source separation KW - Independent component analysis KW - fMRI KW - Resting state KW - Retinotopy KW - Spatio temporal Y1 - 2017 U6 - https://doi.org/10.1016/j.cmpb.2017.08.019 SN - 1872-7565 SN - 0169-2607 VL - 151 SP - 91 EP - 99 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wein, Simon A1 - Deco, Gustavo A1 - Tomé, Ana Maria A1 - Goldhacker, Markus A1 - Malloni, Wilhelm M. A1 - Greenlee, Mark W. A1 - Lang, Elmar Wolfgang T1 - Brain Connectivity Studies on Structure-Function Relationships: A Short Survey with an Emphasis on Machine Learning JF - Computational intelligence and neuroscience N2 - This short survey reviews the recent literature on the relationship between the brain structure and its functional dynamics. Imaging techniques such as diffusion tensor imaging (DTI) make it possible to reconstruct axonal fiber tracks and describe the structural connectivity (SC) between brain regions. By measuring fluctuations in neuronal activity, functional magnetic resonance imaging (fMRI) provides insights into the dynamics within this structural network. One key for a better understanding of brain mechanisms is to investigate how these fast dynamics emerge on a relatively stable structural backbone. So far, computational simulations and methods from graph theory have been mainly used for modeling this relationship. Machine learning techniques have already been established in neuroimaging for identifying functionally independent brain networks and classifying pathological brain states. This survey focuses on methods from machine learning, which contribute to our understanding of functional interactions between brain regions and their relation to the underlying anatomical substrate. KW - Brain Mapping KW - Brain/diagnostic imaging KW - Diffusion Tensor Imaging KW - Machine Learning KW - Magnetic Resonance Imaging KW - Nerve Net/diagnostic imaging KW - Neural Pathways/diagnostic imaging KW - Structure-Activity Relationship Y1 - 2021 U6 - https://doi.org/10.1155/2021/5573740 SP - 1 EP - 31 PB - Hindawi ER - TY - CHAP A1 - Wostmann, Rene A1 - Schlunder, Philipp A1 - Temme, Fabian A1 - Klinkenberg, Ralf A1 - Kimberger, Josef A1 - Spichtinger, Andrea A1 - Goldhacker, Markus A1 - Deuse, Jochen T1 - Conception of a Reference Architecture for Machine Learning in the Process Industry T2 - 2020 IEEE International Conference on Big Data (Big Data): 10.12.2020 - 13.12.2020 Atlanta, GA, USA N2 - The increasing global competition demands continuous optimization of products and processes from companies in the process industry. Where conventional methods of Lean Management and Six Sigma reach their limits, new opportunities and challenges arise through increasing connectivity in the Industrial Internet of Things and machine learning. The majority of industrial projects do not reach the deployment or are isolated solutions, as the structures for data integration, training, deployment and maintenance of models are not established. This paper presents the conception of a reference architecture for machine learning in the process industry to support companies in implementing their own specific structures. The focus is on the development process and an exemplary implementation in the brewing industry. KW - Big data KW - Companies KW - Industrial Internet of Things KW - Industries KW - Machine learning KW - Optimization KW - process industry KW - Production KW - Reference architecture KW - Six sigma KW - Training Y1 - 2020 SN - 978-1-7281-6251-5 U6 - https://doi.org/10.1109/bigdata50022.2020.9378290 SP - 1726 EP - 1735 PB - IEEE ER - TY - JOUR A1 - Plank, Tina A1 - Rosengarth, Katharina A1 - Schmalhofer, Carolin A1 - Goldhacker, Markus A1 - Brandl-Rühle, Sabine A1 - Greenlee, Mark W. T1 - Perceptual learning in patients with macular degeneration JF - Frontiers in psychology N2 - Patients with age-related macular degeneration (AMD) or hereditary macular dystrophies (JMD) rely on an efficient use of their peripheral visual field. We trained eight AMD and five JMD patients to perform a texture-discrimination task (TDT) at their preferred retinal locus (PRL) used for fixation. Six training sessions of approximately one hour duration were conducted over a period of approximately 3 weeks. Before, during and after training twelve patients and twelve age-matched controls (the data from two controls had to be discarded later) took part in three functional magnetic resonance imaging (fMRI) sessions to assess training-related changes in the BOLD response in early visual cortex. Patients benefited from the training measurements as indexed by significant decrease (p = 0.001) in the stimulus onset asynchrony (SOA) between the presentation of the texture target on background and the visual mask, and in a significant location specific effect of the PRL with respect to hit rate (p = 0.014). The following trends were observed: (i) improvement in Vernier acuity for an eccentric line-bisection task; (ii) positive correlation between the development of BOLD signals in early visual cortex and initial fixation stability (r = 0.531); (iii) positive correlation between the increase in task performance and initial fixation stability (r = 0.730). The first two trends were non-significant, whereas the third trend was significant at p = 0.014, Bonferroni corrected. Consequently, our exploratory study suggests that training on the TDT can enhance eccentric vision in patients with central vision loss. This enhancement is accompanied by a modest alteration in the BOLD response in early visual cortex. KW - perceptual learning KW - fMRI BOLD KW - cortical plasticity KW - visual cortex KW - macular degeneration Y1 - 2014 U6 - https://doi.org/10.3389/fpsyg.2014.01189 SN - 1664-1078 VL - 5 SP - 1 EP - 14 PB - Frontiers Research Foundation CY - Lausanne ER - TY - GEN A1 - Greenlee, Mark W. A1 - Anstis, Stuart A1 - Rosengarth, Katharina A1 - Goldhacker, Markus A1 - Brandl-Rühle, Sabine A1 - Plank, Tina T1 - Neural correlates of perceptual filling-in: fMRI evidence in the foveal projection zone of patients with central scotoma T2 - Journal of Vision / Vision Sciences Society Annual Meeting Abstract N2 - Patients with juvenile retinal dystrophy often report that they are unaware of their central scotoma, suggesting the presence of perceptual filling-in. We used functional Magnetic Resonance Imaging (fMRI) to determine possible neural correlates of perceptual filling-in in patients with retinal distrophy and clinically established central scotoma in both eyes. The data of 5 patients (Stargardt disease, cone-rod dystrophy; mean age 45 yrs; scotoma diameter 10-20°) and of 5 normally sighted controls were analyzed. Fixation behaviour and perimetry were measured with a Nidek microperimeter. Magnetic resonance imaging was performed using a Siemens 3T Allegra scanner. We stimulated the central visual field (30 deg) with a vertically oriented, low spatial frequency (1 c/deg) high-contrast sinewave grating that was either a) continuous, or b) was interrupted by a central grey disk. The disk was either slightly larger than the scotoma (detectable on 75% of trials) or slightly smaller (detectable on 25% of trials). To control for attention, an eccentric fixation task was performed during scanning. Data were analyzed using SPM8 (GLM with ROI analysis to obtain percent signal change for foveal projection zone). Results: for all patients, the BOLD signal in the foveal projection area was significantly higher for the small disk (i.e., condition leading to complete filling-in) than for the large disk (i.e., no filling-in). This effect was absent in the control subjects. Our findings support the existence of an active neural process that leads to filling-in in patients with central visual field scotomata. Y1 - 2012 U6 - https://doi.org/10.1167/12.9.1303 SN - 1534-7362 VL - 12 IS - 9 PB - ARVO ER - TY - JOUR A1 - Goldhacker, Markus A1 - Rosengarth, Katharina A1 - Plank, Tina A1 - Greenlee, Mark W. T1 - The effect of feedback on performance and brain activation during perceptual learning JF - Vision research N2 - We investigated the role of informative feedback on the neural correlates of perceptual learning in a coherent-motion detection paradigm. Stimulus displays consisted of four patches of moving dots briefly (500 ms) presented simultaneously, one patch in each visual quadrant. The coherence level was varied in the target patch from near threshold to high, while the other three patches contained only noise. The participants judged whether coherent motion was present or absent in the target patch. To guarantee central fixation, a secondary RSVP digit-detection task was performed at fixation. Over six training sessions subjects learned to detect coherent motion in a predefined quadrant (i.e., the learned location). Half of our subjects were randomly assigned to the feedback group, where they received informative feedback after each response during training, whereas the other group received non-informative feedback during training that a response button was pressed. We investigated whether the presence of informative feedback during training had an influence on the learning success and on the resulting BOLD response. Behavioral data of 24 subjects showed improved performance with increasing practice. Informative feedback promoted learning for motion displays with high coherence levels, whereas it had little effect on learning for displays with near-threshold coherence levels. Learning enhanced fMRI responses in early visual cortex and motion-sensitive area MT+ and these changes were most pronounced for high coherence levels. Activation in the insular and cingulate cortex was mainly influenced by coherence level and trained location. We conclude that feedback modulates behavioral performance and, to a lesser extent, brain activation in areas responsible for monitoring perceptual learning. KW - Perceptual learning KW - Functional MRI KW - Feedback KW - Coherent motion detection Y1 - 2014 U6 - https://doi.org/10.1016/j.visres.2013.11.010 SN - 1878-5646 SN - 0042-6989 VL - 99 SP - 99 EP - 110 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Wein, S. A1 - Tomé, Ana Maria A1 - Goldhacker, Markus A1 - Greenlee, Mark W. A1 - Lang, Elmar Wolfgang T1 - Hybridizing EMD with cICA for fMRI Analysis of Patient Groups T2 - 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC): 23-27 July 2019, Berlin, Germany N2 - Independent component analysis (ICA), as a data driven method, has shown to be a powerful tool for functional magnetic resonance imaging (fMRI) data analysis. One drawback of this multivariate approach is, that it is naturally not convenient for analysis of group studies. Therefore various techniques have been proposed in order to overcome this limitation of ICA. In this paper a novel ICA based work-flow for extracting resting state networks from fMRI group studies is proposed. An empirical mode decomposition (EMD) is used to generate reference signals in a data driven manner, which can be incorporated into a constrained version of ICA (cICA), what helps to overcome the inherent ambiguities. The results of the proposed workflow are then compared to those obtained by a widely used group ICA approach. It is demonstrated that intrinsic modes, extracted by EMD, are suitable to serve as references for cICA to obtain typical resting state patterns, which are consistent over subjects. This novel processing pipeline makes it transparent for the user, how comparable activity patterns across subjects emerge, and also the trade-off between similarity across subjects and preserving individual features can be well adjusted and adapted for different requirements in the new work-flow. KW - biomedical MRI KW - data analysis KW - independent component analysis KW - medical image processing Y1 - 2019 U6 - https://doi.org/10.1109/EMBC.2019.8856355 SP - 194 EP - 197 PB - IEEE ER - TY - JOUR A1 - Goldhacker, Markus A1 - Fellner, Marie-Christin A1 - Volberg, G. A1 - Mullinger, K. J. A1 - Greenlee, Mark W. A1 - Hanslmayr, Simon T1 - Spurious correlations in simultaneous EEG-fMRI driven by in-scanner movement JF - NeuroImage N2 - Simultaneous EEG-fMRI provides an increasingly attractive research tool to investigate cognitive processes with high temporal and spatial resolution. However, artifacts in EEG data introduced by the MR scanner still remain a major obstacle. This study, employing commonly used artifact correction steps, shows that head motion, one overlooked major source of artifacts in EEG-fMRI data, can cause plausible EEG effects and EEG–BOLD correlations. Specifically, low-frequency EEG (< 20 Hz) is strongly correlated with in-scanner movement. Accordingly, minor head motion (< 0.2 mm) induces spurious effects in a twofold manner: Small differences in task-correlated motion elicit spurious low-frequency effects, and, as motion concurrently influences fMRI data, EEG–BOLD correlations closely match motion-fMRI correlations. We demonstrate these effects in a memory encoding experiment showing that obtained theta power (~ 3–7 Hz) effects and channel-level theta–BOLD correlations reflect motion in the scanner. These findings highlight an important caveat that needs to be addressed by future EEG-fMRI studies. Y1 - 2016 U6 - https://doi.org/10.1016/j.neuroimage.2016.03.031 VL - 133 IS - June SP - 354 EP - 366 PB - Elsevier ER - TY - JOUR A1 - Wein, Simon A1 - Tomé, Ana Maria A1 - Goldhacker, Markus A1 - Greenlee, Mark W. A1 - Lang, Elmar Wolfgang T1 - A Constrained ICA-EMD Model for Group Level fMRI Analysis JF - Frontiers in Neuroscience N2 - Independent component analysis (ICA), being a data-driven method, has been shown to be a powerful tool for functional magnetic resonance imaging (fMRI) data analysis. One drawback of this multivariate approach is that it is not, in general, compatible with the analysis of group data. Various techniques have been proposed to overcome this limitation of ICA. In this paper, a novel ICA-based workflow for extracting resting-state networks from fMRI group studies is proposed. An empirical mode decomposition (EMD) is used, in a data-driven manner, to generate reference signals that can be incorporated into a constrained version of ICA (cICA), thereby eliminating the inherent ambiguities of ICA. The results of the proposed workflow are then compared to those obtained by a widely used group ICA approach for fMRI analysis. In this study, we demonstrate that intrinsic modes, extracted by EMD, are suitable to serve as references for cICA. This approach yields typical resting-state patterns that are consistent over subjects. By introducing these reference signals into the ICA, our processing pipeline yields comparable activity patterns across subjects in a mathematically transparent manner. Our approach provides a user-friendly tool to adjust the trade-off between a high similarity across subjects and preserving individual subject features of the independent components. Y1 - 2020 U6 - https://doi.org/10.3389/fnins.2020.00221 SN - 1662-453X SN - 1662-4548 VL - 14 SP - 1 EP - 10 PB - frontiers ER - TY - JOUR A1 - Goldhacker, Markus A1 - Al-Subari, Karema A1 - Al-Baddai, Saad A1 - Tomé, Ana Maria A1 - Faltermeier, Rupert A1 - Lang, Elmar Wolfgang T1 - EMDLAB: A toolbox for analysis of single-trial EEG dynamics using empirical mode decomposition JF - Journal of Neuroscience Methods N2 - Background: Empirical mode decomposition (EMD) is an empirical data decomposition technique. Recently there is growing interest in applying EMD in the biomedical field. New method: EMDLAB is an extensible plug-in for the EEGLAB toolbox, which is an open software environment for electrophysiological data analysis. Results: EMDLAB can be used to perform, easily and effectively, four common types of EMD: plain EMD, ensemble EMD (EEMD), weighted sliding EMD (wSEMD) and multivariate EMD (MEMD) on EEG data. In addition, EMDLAB is a user-friendly toolbox and closely implemented in the EEGLAB toolbox. Comparison with existing methods: EMDLAB gains an advantage over other open-source toolboxes by exploiting the advantageous visualization capabilities of EEGLAB for extracted intrinsic mode functions (IMFs) and Event-Related Modes (ERMs) of the signal. Conclusions: EMDLAB is a reliable, efficient, and automated solution for extracting and visualizing the extracted IMFs and ERMs by EMD algorithms in EEG study. Y1 - 2015 U6 - https://doi.org/10.1016/j.jneumeth.2015.06.020 VL - 253 IS - September SP - 193 EP - 205 PB - Elsevier CY - AMsterdam ER - TY - CHAP A1 - Goldhacker, Markus A1 - Tomé, Ana Maria A1 - Greenlee, Mark W. A1 - Lang, Elmar Wolfgang T1 - Early meta-level: deeper understanding of connectivity-states and consequences for state definition T2 - 21st Annual Meeting of the Organization for Human Brain Mapping, June 14-18, 2015, Honolulu, Hawaii Y1 - 2015 U6 - https://doi.org/10.13140/RG.2.1.2561.3929 PB - Academic Press CY - San Diego, CA ER - TY - VIDEO A1 - Al-Subari, Karema A1 - Al-Baddai, Saad A1 - Tomé, Ana Maria A1 - Goldhacker, Markus A1 - Faltermeier, Rupert A1 - Lang, Elmar Wolfgang T1 - EMDLAB-toolbox- tutorial video Y1 - 2015 UR - https://www.researchgate.net/publication/280492172_EMDLAB-toolbox-_tutorial_video ER - TY - JOUR A1 - Greenlee, Mark W. A1 - Rosengarth, Katharina A1 - Schmalhofer, Carolin A1 - Goldhacker, Markus A1 - Brandl-Rühle, Sabine A1 - Plank, Tina T1 - Perceptual learning in patients with central scotomata due to hereditary and age-related macular dystrophy JF - Journal of Vision N2 - Hereditary and age-related forms of macular dystrophy (MD) are characterized by loss of cone function in the fovea, leading to central scotomata and eccentric fixation at the so-called preferred retinal locus (PRL). We investigated whether perceptual learning enhances visual abilities at the PRL. We also determined the neural correlates (3-Tesla fMRI) of learning success. Twelve MD patients (eight with age-related macular dystrophy, four with hereditary macular dystrophies) were trained on a texture discrimination task (TDT) over six days. Patients underwent three fMRI sessions (before, during and after training) while performing the TDT (target at PRL or opposite PRL). Reading speed, visual acuity (Vernier task) and contrast sensitivity were also assessed before and after training. With one exception, all patients showed improved performance (i.e. significant decrease in stimulus onset asynchronies and reaction times, significant increase in hit rates) on the TDT. Eight patients also showed moderate increases in reading speed, six patients showed improved thresholds in contrast sensitivity and nine patients showed improved thresholds in a vernier visual acuity task after TDT training. We found an increase in BOLD response in the projections zone of the PRL in the primary visual cortex in nine of twelve patients after training. The change in fMRI signal correlated (r = .8; p = .02) with the patients’ performance enhancements when the target was in the PRL. The results suggest that perceptual learning can enhance eccentric vision and cortical processing in MD patients. Y1 - 2014 U6 - https://doi.org/10.1167/14.10.666 SN - 1468-4233 SN - 0301-0066 VL - 14 IS - 10 PB - ARVO ER - TY - JOUR A1 - Goldhacker, Markus A1 - Rosengarth, Katharina A1 - Anstis, Stuart A1 - Wirth, Anna A1 - Plank, Tina A1 - Greenlee, Mark W. T1 - FMRI evidence for perceptual filling-in in patients with macular dystrophy JF - Perception Y1 - 2013 UR - https://www.researchgate.net/publication/298247764_FMRI_evidence_for_perceptual_filling-in_in_patients_with_macular_dystrophy SN - 1468-4233 SN - 0301-0066 VL - 42 SP - 72 EP - 73 ER -