1,720,996 research outputs found
Laboratory of functional neuroelectrical imaging and brain computer interfacing at Fondazione Santa Lucia
No full textQuantitative EEG patterns following unilateral stroke: A study in chronic stage
No full textThe aim of this study was to investigate the EEG power spectra obtained during rest and mental processing in chronic stroke patients. Seventeen patients with stabilized unilateral cerebral ischemia, grouped according to the side of lesion, underwent quantitative EEG recordings during rest and attentive/cognitive tasks. EEG spectral values were compared with those of 11 healthy subjects. Patients displayed different EEG patterns from controls, under rest condition: patients with left hemispheric lesion were characterized by a preserved alpha and beta band "reactivity," with a lack of significant changes in slow band components. In patients with right hemisphere lesion, no significant changes of the slow and fast band activities were evident during each task These findings indicate that different EEG patterns of activation characterize stroke patients with left and right hemispheric damage
Motor-related cortical dynamics to intact movements in tetraplegics as revealed by high-resolution EEG
No full textWe explored the cortical dynamics during movements of an unaffected body part in tetraplegic subjects with chronic spinal cord injury (SCI). The aims were to find out whether the intact movements were associated with a physiological time-varying pattern of activity in the motor-related cortical areas and whether the primary motor area (MI) activation followed a somatotopic distribution. Event-related potentials to self-initiated lip movements were analyzed by means of cortical source imaging of EEG recorded from seven tetraplegic subjects and seven control subjects. Regions of interest (ROIs) were selected on individual MRI and the time-varying electrophysiologic activity (cortical current density, CCD) was estimated on these ROIs and subjected to across-subject analysis. A significant, bilateral movement-related pattern of MI activation was detected during motor task execution in SCI patients as well as in controls. The site of local maxima activation displayed a symmetrical discrete distribution within MI, consistently with a putative somatotopic lip representation, in all the subjects. The supplementary motor area proper (SMAp) was always coactivated with MI and coactivation was characterized by a time course with typical premotion and motion phases over both motor areas. A clear-cut temporal delay between the SMAp and MI activation did not occur either in SCI patients or in controls. These findings obtained with noninvasive neuroelectrical source imaging document that in chronic SCI subjects "executive" motor areas are engaged with a preserved temporal and spatial pattern during preparation and execution of intact movements
Multimodal integration of EEG, MEG and fMRI data for the solution of the neuroimage puzzle
No full textIn this paper, advanced methods for the modeling of human cortical activity from combined high-resolution electroencephalography (EEG), magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) data are presented. These methods include a subject's multicompartment head model (scalp, skull, dura mater, cortex) constructed from magnetic resonance images, multidipole source model and regulafized linear inverse source estimates of cortical current density. Determination of the priors in the resolution of the linear inverse problem was per-formed with the use of information from the hemodynamic responses of the cortical areas as revealed by block-designed (strength of activated voxels) fMRI. Examples of the application of these methods to the estimation of the time varying cortical current density activity in selected region of interest (ROI) are presented for movement-related high-resolution EEG data. (C) 2004 Elsevier Inc. All rights reserved
Motor cortical responsiveness to attempted movements in tetraplegia: Evidence from neuroelectrical imaging
No full textOBJECTIVE: The maintenance of a motor cortical program in the temporal domain is relevant to current neuroinformatic efforts to use non-invasive EEG signals to control neuroprosthetic devices designed to restore natural movements of paralyzed body parts. Here we use an advance neuroelectrical imaging approach to examine the motor cortical responsiveness in human tetraplegia. METHODS: High resolution-electroencephalographic (EEG) recordings were performed in five subjects with tetraplegia due to chronic, complete spinal cord injuries (SCIs) while they attempted self-generated movements of a plegic body part (foot), and in five healthy subjects executing simple foot movements. RESULTS: Self-generated movement attempts induced significant EEG sources of activity in a set of motor-related areas (including the primary motor area, MI) similar to what observed during the preparatory stages of movement execution (control subjects). Functional connectivity showed a preferential interaction between the "non-primary" motor areas and the putative MI foot site, as estimated for both motor execution and attempt. Under this latter condition however, it could be observed an "enlargement" of the functional network by including the left superior parietal cortex. CONCLUSIONS: Our findings indicate the existence of a functional circuit subserving the attempted motion in SCI subjects that encompasses a set of areas known to play a role in motor execution, yet reveals differences in the functional interaction between these areas. SIGNIFICANCE: The understanding of changes in the motor circuitry is relevant to current neuroinformatic efforts to use non-invasive EEG signals to control neuroprosthetic devices designed to benefit paralyzed persons
Estimation of cortical activity from noninvasive high-resolution EEG recordings
No full textThe aim of this paper is to analyze whether the use of the cortical activity estimated from noninvasive EEG recordings could be useful to detect mental states related to the imagination of limb movements. Estimation of cortical activity was performed on high-resolution EEG data related to the imagination of limb movements gathered in five normal, healthy subjects by using realistic head models. Cortical activity was estimated in region of interest (ROI) associated with the subject's Brodmann areas (BAs) by using depth-weighted minimum norm solutions. Comparisons between surface recorded EEG and the estimated cortical activity were performed. The estimated cortical activity related to the mental imagery of limbs in the five subjects is located mainly over the contralateral primary motor area. The unbalance between brain activity estimated in contralateral and ipsilateral motor cortical areas relative to the finger movement imagination is greater than those obtained in the scalp EEG recordings. Results suggest that the use of the estimated cortical activity for the motor imagery of upper limbs could be potentially superior with respect to the use of surface EEG recordings. This is due to a greater statistically significant unbalance between the activity estimated in the contralateral and ipsilateral hemisphere with respect to those observed with surface EEG. These results are useful in the context of the development of a noninvasive Brain Computer Interface. (C) 2004 Elsevier B.V. All rights reserved
Cortical Network Dynamics during Foot Movements.
No full textThe present work intends to evaluate the dynamics of the cerebral networks during the preparation and the execution of the foot movement. In order to achieve this objective, we have used mathematical tools capable of estimating the cortical activity via high-resolution EEG techniques. Afterwards we estimated, the instantaneous relationships occurring among the time-series of sixteen regions of interest (ROIs) in the Alpha (7–12 Hz) and Beta (13–29 Hz) band through the adaptive multivariate autoregressive models. Eventually, we evaluated the weightedtopology of the cerebral networks by calculating some theoretical graph indexes. The results show that the main structural changes are encoded in the highest spectral contents (Beta band). In particular, during the execution of the foot movement the cingulate motor areas (CM) work as network “hubs” presenting a large amount of outgoing links to the other ROIs. Moreover, the connectivity pattern changes its structure according to the different temporal stages of the task. In particular, the communication between the ROIs reaches its highest level of efficiency during the preparation of the foot movement, as revealed by the “small-world” property of the network, which is characterized by the presence of abundant clustering connections combined with short average distances between the cortical area
Non-invasive brain-computer interface system to operate assistive devices
No full textIn this pilot study, a system that allows disabled persons to improve or recover their mobility and communication within the surrounding environment was implemented and validated. The system is based on a software controller that offers to the user a communication interface that is matched with the individual's residual motor abilities. Fourteen patients with severe motor disabilities due to progressive neurodegenerative disorders were trained to use the system prototype under a rehabilitation program. All users utilized regular assistive control options (e.g., microswitches or head trackers) while four patients learned to operate the system by means of a non-invasive EEG-based Brain-Computer Interface, based on the subjects' voluntary modulations of EEG sensorimotor rhythms recorded on the scalp
Cortical causality patterns during the execution of a Stroop task in normal subjects by using multimodal integration of high resolution EEG and fMRI recordings
No full textExtracting information from cortical connectivity patterns estimated from high resolution EEG recordings: A theoretical graph approach
No full textOver the last 20 years, a body of techniques known as high resolution EEG has allowed precise estimation of cortical activity from non-invasive EEG measurements. The availability of cortical waveforms from non-invasive EEG recordings allows to have not only the level of activation within a single region of interest (ROI) during a particular task, but also to estimate the causal relationships among activities of several cortical regions. However, interpreting resulting connectivity patterns is still an open issue, due to the difficulty to provide an objective measure of their properties across different subjects or groups. A novel approach addressed to solve this difficulty consists in manipulating these functional brain networks as graph objects for which a large body of indexes and tools are available in literature and already tested for complex networks at different levels of scale (Social, WorldWide-Web and Proteomics). In the present work, we would like to show the suitability of such approach, showing results obtained comparing separately two groups of subjects during the same motor task and two different motor tasks performed by the same group. In the first experiment two groups of subjects (healthy and spinal cord injured patients) were compared when they moved and attempted to move simultaneously their right foot and lips, respectively. The contrast between the foot-lips movement and the simple foot movement was addressed in the second experiment for the population of the healthy subjects. For both the experiments, the main question is whether the "architecture" of the functional connectivity networks obtained could show properties that are different in the two groups or in the two tasks. All the functional connectivity networks gathered in the two experiments showed ordered properties and significant differences from "random" networks having the same characteristic sizes. The proposed approach, based on the use of indexes derived from graph theory, can apply to cerebral connectivity patterns estimated not only from the EEG signals but also from different brain imaging methods
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