sLORETA Method Research Articles

Source localization of mu-rhythm event related desynchronization in EEG during tactile imagery

Tactile imagery remains a relatively understudied phenomenon in the field of mental imagery research. However, alongside motor imagery, this technique holds promise as an effective tool for sensorimotor rehabilitation following stroke and spinal cord injuries. In this study, conducted with 22 healthy volunteers, we investigated the source localization of mu-rhythm event related desynchronization (Event-Related Desynchronization, ERD) using multi-channel electroencephalogram recordings and subsequent inverse problem solution with the sLORETA method. All participants exhibited ERD during tactile imagery task, as well as under vibrotactile stimulation. It was demonstrated that mu-rhythm ERD during vibrotactile stimulation, as well as tactile imagery, was localized in the sensorimotor areas of the contralateral hemisphere. Within the source space, ERD in the postcentral gyrus was significantly stronger compared to the precentral gyrus. These findings indicate that tactile imagery, akin to the perception of real tactile stimuli, leads to prominent activation of sensorimotor cortical areas, consistent with the general understanding of the shared neural substrate during mental imagery and perception.

Functional features of the mirror neuron system during action observation and execution in patients with anxiety and depressive symptoms

The perception and comprehension of non-verbal information and body language in humans and higher primates are realized by the mirror neuron system (MNS). Anxiety and depressive symptoms may change social perception, which could manifest as functional changes in the MNS. In this paper, using the inverse electroencephalography (EEG) problem and rhythm suppression, we investigated spatial and frequency distortions of the MNS in 24 patients exhibiting depressive and anxiety symptoms and 23 controls. EEG was recorded during four motor tasks: action observation (where participants observed a hand gesture performed by a demonstrator), imagination, execution, and joint execution (simultaneous execution with the demonstrator). Mu suppression was employed across a wide frequency and spatial range to assess the level of MNS activity, while the sLORETA method was employed to localize the activity sources. The results indicate that the patients demonstrated task-selective mu suppression mainly during observation and joint execution in the frontal, central, and occipital areas of the cortex across a wide frequency range. In contrast, the controls demonstrated clear and pronounced mu rhythm suppression in the central regions of the brain in the upper-frequency range (10.5 – 13 Hz) during all mirroring tasks. These results suggest that patients with anxiety and depressive symptoms engage additional neural resources to complete social tasks, particularly involving auxiliary neural networks located in the frontal associative arrays and visual cortex.

Current source density (sLORETA) in patients undergoing cognitive rehabilitation using dual task in the early postoperative period of coronary artery bypass grafting

Highlights. For the first time, the method of standardized low resolution electromagnetic tomography – sLORETA was used to assess the neurophysiological correlates of the success of cognitive rehabilitation using dual task to recover the brain functions affected by ischemia during cardiac surgery.The patients who were successfully rehabilitated have demonstrated lower postoperative values of resting state theta activity within the right hemisphere, indicating the transfer effect, which is an important component of successful cognitive rehabilitation.Aim. Visualization and monitoring of brain ischemia is important for the diagnosis of cerebrovascular diseases. The aim of the study was to evaluate the possibilities and applicability of the method of standardized low resolution electromagnetic brain tomography – sLORETA for analyzing brain electrical activity in patients undergoing cognitive rehabilitation using dual tasks to recover impaired brain functions during ischemia associated with cardiac surgery.Methods. The study included 16 male patients (45–75 years old) who were admitted for planned coronary artery bypass grafting (CABG) to the Clinic at the Research Institute for Complex Issues of Cardiovascular Diseases. Clinical and neurophysiological examinations were performed 2–3 days before CABG and 1 week after surgery. All patients underwent cognitive rehabilitation that started at postoperative day 3 or 4 and lasted until discharge, the outcome was assessed as well. Monopolar EEG (62 channels) was recorded at rest in a sitting position with eyes closed in a light- and noise-insulated room using a Neuvo SynAmps2 Amplifier. Data processing of EEG background activity for sLORETA analysis was performed using the EEGLAB in MATLAB software (The MathWorks, Natick, MA, USA). The sLORETA algorithms were used to calculate dynamic cross spectrum and current source density within the analyzed frequency range (4–6 Hz). Statistical analysis of current source density indicators was carried out by using the method of statistical non-parametric mapping in the sLORETA software package, and the difference between the current source density in the pre- and postoperative period (after cognitive rehabilitation) was calculated as well.Results. Cognitive rehabilitation was successful in 44% (7 patients) of cases. The differences have been revealed between the groups with successful and unsuccessful cognitive rehabilitation by using sLORETA. The group with unsuccessful cognitive rehabilitation demonstrated higher current source density estimates in theta rhythm compared with the successful rehabilitation group, it was most pronounced (t>- 8.42; p<0.004) in the right hemisphere – Brodmann area 22, temporal lobe and superior temporal gyrus.Conclusion. The sLORETA method demonstrated the positive effect of cognitive training on changes in the spatial patterns of brain activity in patients undergoing onpump CABG. The successful cognitive rehabilitation was associated with lower postoperative resting state theta activity within the right hemisphere, indicating the transfer effect, which is an important component of successful cognitive rehabilitation.

Abnormal Properties of Cortical Functional Brain Network in Major Depressive Disorder: Graph Theory Analysis Based on Electroencephalography-Source Estimates

Studies of scalp electroencephalography (EEG) had shown altered topological organization of functional brain networks in patients with major depressive disorder (MDD). However, most previous EEG-based network analyses were performed at sensor level, while the interpretation of obtained results was not straightforward due to volume conduction effect. To reduce the impact of this defect, the whole cortical functional brain networks of MDD patients were studied during resting state based on EEG-source estimates in this paper. First, scalp EEG signals were recorded from 19 patients with MDD and 20 normal controls under resting eyes-closed state, and cortical neural signals were estimated by using sLORETA method. Then, the correntropy coefficient of wavelet packet coefficients was performed to calculate functional connectivity (FC) matrices in four different frequency bands: δ, θ, α, β, respectively. Afterwards, topological properties of brain networks were analyzed by graph theory approaches. The results showed that the global FC strength of MDD patients was significantly higher than that of healthy subjects in α band. Also, it was found that MDD patients have abnormally increased clustering coefficient and local efficiency in both α and β bands compared to normal people. Furthermore, patients with MDD exhibited increased nodal clustering coefficients in the left lingual gryus and left precuneus in α band. In addition, β band global clustering coefficient was positively correlated with the scores of depression severity. Therefore, the findings indicated the cortical functional brain networks in MDD patients were disruptions, which suggested it would be one of potential causes of depression.

EEG effective connectivity during the first year of life mirrors brain synaptogenesis, myelination, and early right hemisphere predominance

IntroductionThe maturation of electroencephalogram (EEG) effective connectivity in healthy infants during the first year of life is described. MethodsParticipants: A cross-sectional sample of 125 healthy at-term infants, from 0 to 12 months of age, underwent EEG in a state of quiet sleep. Procedures: The EEG primary currents at the source were described with the sLoreta method. An unmixing algorithm was applied to reduce the leakage, and the isolated effective coherence, a direct and directed measurement of information flow, was calculated. Results and DiscussionInitially, the highest indices of connectivity are at the subcortical nuclei, continuing to the parietal lobe, predominantly the right hemisphere, then expanding to temporal, occipital, and finally the frontal areas, which is consistent with the myelination process. Age-related connectivity changes were mostly long-range and bilateral. Connections increased with age, mainly in the right hemisphere, while they mainly decreased in the left hemisphere. Increased connectivity from 20 to 30 Hz, mostly at the right hemisphere. These findings were consistent with right hemisphere predominance during the first three years of life. Theta and alpha connections showed the greatest changes with age. Strong connectivity was found between the parietal, temporal, and occipital regions to the frontal lobes, responsible for executive functions and consistent with behavioral development during the first year. The thalamus exchanges information bidirectionally with all cortical regions and frequency bands. ConclusionsThe maturation of EEG connectivity during the first year in healthy infants is very consistent with synaptogenesis, reductions in synaptogenesis, myelination, and functional and behavioral development.

Localization of Sources Generating the EEG α Rhythm during Observation, Performance, and Imitation of Operant Movements in Subjects with Different Intelligence Levels

Use of the sLORETA method in 62 adult subjects with different intelligence levels located sources generating rhythms in the frequency band 8–12 Hz during observation, performance, and imitation of circular movements with a computer mouse by the experimenter. A relationship between the level of intelligence and differences in the spatial patterns of cerebral cortex activation during performance and imitation of movements was seen. More marked and localized activation of neocortical structures was seen in adult subjects with high levels of general intelligence. Differences in the activation of cortical areas in groups with different general intelligence levels were largely mediated by structures in the right hemisphere, which is involved in processes of visuomotor coordination and the discrimination of own from others’ actions. The greater involvement of the precentral, cingulate, and postcentral gyri of the left hemisphere in the process of imitating the experimenter’s movements in the group with high intelligence may point to a higher level of activation of the mirror system of the brain.

Source localization of epileptic spikes using Multiple Sparse Priors

ObjectiveTo evaluate epileptic source estimation using multiple sparse priors (MSP) inverse method and high-resolution, individual electrical head models. MethodsAccurate source localization is dependent on accurate electrical head models and appropriate inverse solvers. Using high-resolution, individual electrical head models in fifteen epilepsy patients, with surgical resection and clinical outcome as criteria for accuracy, performance of MSP method was compared against standardized low-resolution brain electromagnetic tomography (sLORETA) and coherent maximum entropy on the mean (cMEM) methods. ResultsThe MSP method performed similarly to the sLORETA method and slightly better than the cMEM method in terms of success rate. The MSP and cMEM methods were more focal than sLORETA with the advantage of not requiring an arbitrary selection of a hyperparameter or thresholding of reconstructed current density values to determine focus. MSP and cMEM methods were better than sLORETA in terms of spatial dispersion. ConclusionsResults suggest that the three methods are complementary and could be used together. In practice, the MSP method will be easier to use and interpret compared to sLORETA, and slightly more accurate and faster than the cMEM method. SignificanceSource localization of interictal spikes from dense-array electroencephalography data has been shown to be a reliable marker of epileptic foci and useful for pre-surgical planning. The advantages of MSP make it a useful complement to other inverse solvers in clinical practice.

F191. Electrophysiological brain activity during motor imagery enhanced by brain–computer interface in healthy volunteers and post-stroke patients

Introduction Motor imagery (MI) has been shown to be an effective tool in rehabilitation of post-stroke patients. MI can be enhanced by kinesthetic feedback provided by brain-computer-exoskeleton interfaces. Description and analysis of brain activity during the kinesthetic imagery of movements in healthy subjects and post-stroke patients with the subcortical location of the damage was performed in the current study. Methods Seven right-handed healthy volunteers (age 29 [22.0; 35.0] years) and nine post-stroke patients (age 52.0 [36.0; 58.0] years, time since stroke 6.0 [4.0; 13.0] months) were enrolled. They were trained in kinesthetic motor imagery using brain-computer interface (BCI) and a controllable exoskeleton. All participants had 20 training sessions with a duration of up to 15 min. The BCI was controlled using a Bayessian classifier, which was preset to recognize the imagery of left or right hand extension and the rest state. Processing of EEG recordings was performed using the independent component analysis. The digitization of EEG-electrode positions for obtaining their coordinates in the MRI-related system was made using an NBS Eximia Nexstim device for navigational transcranial magnetic stimulation. This study used the AMICA method to find the sources of electrophysiological brain activity during motor imagery. For each component determined, the EEG inverse problem was solved according to the sLORETA method. Results Components that are most frequently identified by the AMICA method were revealed in the same areas in both groups: SIL (the primary somatosensory left cortex), SIR (the primary somatosensory right cortex), PRC (the precuneus), PRM (the premotor left cortex), and SMA (the supplementary motor area). There were differences in the activity characteristics when comparing healthy controls and patients: the μ -rhythm in the somatosensory area was characterized by a lower frequency in the studied poststroke patients than in the healthy subjects; it had a poorly pronounced peak in all mental states and was only slightly suppressed during contralateral hand motor imagery. The rhythm in the α -band was also characterized by a low frequency with a poorly pronounced peak in the precuneus and premotor area; however, unlike in the healthy subjects, this rhythm increased, i.e., was synchronized, during motor imagery. Conclusion This study is an extension of previous investigations of EEGs during motor imagery in healthy subjects. Only two symmetrical sources in the primary somatosensory cortex were previously discussed. This study revealed three more sources: the premotor area, precuneus, and supplementary motor area. The characteristics of the EEG sources during motor imagery are fundamentally different in post-stroke patients comparing to healthy controls. Funding was provided by grant RFMEF N I60715X0128.

Functioning features of the mirror neuron system in patients with affective disorders

To reveal EEG patterns and activation of neural network changes during perception and realization of a simple motor act in healthy subjects and patients with affective disorders. The patient group consisted of 15 people with affective disorders, the control group included 11 normals. As task subjects were asked to observe the movement of the experimenter hand (clenching of the hand), then submit this motion and then repeat it by themselves. EEG recording and EEG analysis were conducted. To identify activation areas, sLORETA method was used for solving the inverse problem of EEG. In patients with affective disorders, the activation of the brain mirror system occurred in the left temporal region, while in healthy people such activation was observed in the temporal lobes of the two hemispheres and in the frontal upper, middle and lower convolutions.

Double dissociation between the neural correlates of the general and specific factors of the Life Orientation Test-Revised.

In this article, we explore the neural correlates of the general and specific factors assessed by the Life Orientation Test-Revised. These factors have been shown to assess general optimism (GO) and a form of self-enhancement akin to unrealistic optimism (SP). Toward our aim, we used a standardized low-resolution brain electromagnetic tomography (sLORETA), which provides electroencephalographic (EEG) localization measures that are independent of recording reference. Resting-EEG and self-report measures of GO and SP were collected from 51 female undergraduates. EEGs were recorded across 29 scalp sites. Anterior and posterior source alpha asymmetries of cortical activation were obtained by using the sLORETA method. On the basis of previous research findings, ten frontal and six parietal regions of interest (ROIs) were derived. Alpha asymmetry in the posterior cingulate (i.e., BA31) was uniquely associated with GO. In contrast, SP was associated with areas of the inferior frontal gyrus (BA44, BA45) and with the left subcentralis area (BA43). Theoretical and practical implications of the findings are provided and discussed.

Simulation of Extended Source Localization using sLORETA Method for Magnetocardiography

Simulation of Extended Source Localization using sLORETA Method for Magnetocardiography

Evaluation of spatial resolution and noise sensitivity of sLORETA method for EEG source localization using low-density headsets

Electroencephalography (EEG) has enjoyed considerable attention over the past century and has been applied for diagnosis of epilepsy, stroke, traumatic brain injury and other disorders where 3D localization of electrical activity in the brain is potentially of great diagnostic value. In this study we evaluate the precision and accuracy of spatial localization of electrical activity in the brain delivered by a popular reconstruction technique sLORETA applied to EEG data collected by two commonly used low-density headsets with 14 and 19 measurement channels, respectively. Numerical experiments were performed for a realistic head model obtained by segmentation of MRI images. The EEG source localization study was conducted with a simulated single active dipole, as well as with two spatially separated simultaneously active dipoles, as a function of dipole positions across the neocortex, with several different noise levels in the EEG signals registered on the scalp. The results indicate that while the reconstruction accuracy and precision of the sLORETA method are consistently high in the case of a single active dipole, even with the low-density EEG configurations considered in the present study, successful localization is much more problematic in the case of two simultaneously active dipoles. The quantitative analysis of the width of the reconstructed distributions of the electrical activity allows us to specify the lower bound for the spatial resolution of the sLORETA-based 3D source localization in the considered cases.

A novel approach for multiscale source analysis and modeling of epileptic spikes.

Multiscale recordings of brain electrical activity are often performed for presurgical evaluation in patients with focal epilepsy to facilitate the identification and precise delineation of the epileptogenic zone. However, data regarding the concordance of source models derived from recordings on different scales and their reciprocal validation against clinical outcomes remains scarce. This study aims to define a common source model that accurately depicts both scalp EEG and subdural EEG (ECoG) interictal spikes. To this purpose, the sLORETA method was applied to averaged spikes and source reconstruction results were implemented to outline the location and extent of an epileptic cortical patch. This estimated patch served as the basis for the spatiotemporal source model in a generative model of EEG. Spike activity was simulated on both scalp EEG and ECoG signal scales, with simulated traces resembling measured traces regarding their spatial distribution and amplitude compared to background. Simulated spikes served for the evaluation of source reconstruction with a known generator topography. The described setup allows for the validation and, ultimately, for the refinement of source reconstruction methods. It provides novel insights towards a thorough understanding of physiological and pathological brain processes and their representation in neuroelectric measurements.

Relations among EEG-alpha asymmetry, BIS/BAS, and dispositional optimism

Past research has been unable to address whether the activity in the frontal hemispheres is related to the direction of motivation (approach versus withdrawal) or valence of emotion (positive versus negative). The present study was an attempt to address this question by using a standardized low-resolution brain electromagnetic tomography (sLORETA) which provides EEG localization measures that are independent of the recording reference. Resting EEG, self-report measures of Behavioral Activation and Inhibition System (BAS and BIS) strength, dispositional optimism and a measure of hedonic tone, were collected from 51 unselected undergraduates. Three measures of cortical activation were obtained: (a) alpha asymmetry at conventional scalp sites, (b) anterior and posterior source alpha asymmetries (sLORETA method), (c) posterior versus frontal delta and theta activity. Both alpha asymmetry measures (conventional EEG and sLORETA) yielded significant frontal and parietal asymmetry correlation patterns. Neither measure identified significant associations between resting posterior versus frontal delta and theta activity personality traits. Higher BAS was uniquely related to greater left-sided activation in the middle frontal gyrus (BA11). Optimism was associated with higher activations in the left-superior frontal gyrus (BA10) and in the right-posterior cingulate cortex (BA31).

MEG and fMRI imaging of striatal and orbitofrontal involvement in rewards processing

Event Abstract Back to Event MEG and fMRI imaging of striatal and orbitofrontal involvement in rewards processing Eliezer Kanal1*, Robert Sclabassi2, Wenyan Jia3, Mingui Sun3 and Anto Bagic4 1 Carnegie Mellon University, United States 2 Computational Diagnostics, Inc., United States 3 University of Pittsburgh, United States 4 University of Pittsburgh Medical Center, United States Human reward processing involves neural regions located in both superifical and deep regions of the brain. Recruitment of these regions during reward processing has been successfully observed using fMRI. However, such studies typically possess very low temporal resolution. In this study we attempted to replicate an existing fMRI study which successfully activated the rewards system using a gambling task and examine this activity using both MEG and fMRI. The fMRI portion component successfully replicated the results, indicating that the striatum, orbitofrontal cortex (OFC), and anterior cingulate cortex (ACC) was significantly active during the gambling task. Using the exSSS method, we were able to successfully observe this activity as well in the MEG. Source localization for the three aforementioned regions was performed using the sLORETA method. Granger causality analysis of these three regions demonstrated a granger-causal relationship from the striatum to both the ACC and OFC, and a second granger-causal relationship between the OFC and the ACC. This paper marks the first MEG recording of a granger-causal neural network involving both deep and more superficial regions in which all activation is verified by fMRI findings. Additionally, these findings demonstrate the efficacy of the exSSS method as a viable tool for deep neural imaging via MEG. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: Instrumentation and Multi-modal Integrations: MEG, Low-field MRI,EEG, fMRI,TMS,NIRS Citation: Kanal E, Sclabassi R, Jia W, Sun M and Bagic A (2010). MEG and fMRI imaging of striatal and orbitofrontal involvement in rewards processing. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00024 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Mar 2010; Published Online: 19 Mar 2010. * Correspondence: Eliezer Kanal, Carnegie Mellon University, Pittsburgh, United States, eykanal@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Eliezer Kanal Robert Sclabassi Wenyan Jia Mingui Sun Anto Bagic Google Eliezer Kanal Robert Sclabassi Wenyan Jia Mingui Sun Anto Bagic Google Scholar Eliezer Kanal Robert Sclabassi Wenyan Jia Mingui Sun Anto Bagic PubMed Eliezer Kanal Robert Sclabassi Wenyan Jia Mingui Sun Anto Bagic Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.