Biomedical subjects

Claudio Babiloni

Publications and source records attributed to Claudio Babiloni.

At least 37 records · Page 2Linked to original sources

PubMed2005

Slow cortical potential shifts preceding sensorimotor interactions.

It is well known that synchronization of cortical neurons is modulated ("gating") by the chronological interaction between somatosensory and sensorimotor events. This study tested the hypothesis that the anticipatory processes for this interaction increase the synchronization of cortical neurons as revealed by negative event-related potentials (contingent negative variation, CNV). High-resolution electroencephalographic data (128 electrodes) were recorded in 14 subjects. In the "sensorimotor interaction" condition, the subjects were waiting for a galvanic somatosensory stimulation at the left hand concomitant with a Go or NoGo stimulus (50% of Go trials triggering right hand movements). In the control condition, the Go/NoGo stimulus followed the somatosensory stimulation of 1.5s. The electroencephalographic data were spatially enhanced by surface Laplacian estimation. In the control condition, the CNV was observed only in the foreperiod between the somatosensory stimulation and Go/NoGo task (i.e. no CNV before the somatosensory stimuli). It was spatially localized in the primary sensorimotor area contralateral to the possible motor response. In the "sensorimotor interaction" condition, the CNV preceded the concomitant somatosensory stimulation and Go/NoGo task and was distributed to the frontocentral midline other than the contralateral sensorimotor area. These results suggest that the anticipatory processes for sensorimotor interactions increase the synchronization of cortical neurons in the frontocentral midline, possibly due to mechanisms sub-serving top-down attentional processes.

Adult↗

PubMed2005

Visuo-spatial consciousness and parieto-occipital areas: a high-resolution EEG study.

Conscious and unconscious visuo-spatial processes are mainly related to parieto-occipital cortical activation. In this study, the working hypothesis was that a specific pattern of parieto-occipital activation is induced by conscious, as opposed to unconscious, visuo-spatial processes. Electroencephalographic data (128 channels) were recorded in 12 normal adults during a visuo-spatial task. A cue stimulus appeared on the right or the left (equal probability) monitor side for a 'threshold time' inducing approximately 50% of correct recognitions. It was followed (after 2 s) by visual go stimuli at spatially congruent or incongruent positions with reference to the cue location. The left (right) mouse button was clicked if the go stimulus appeared on the left (right) monitor side. Subjects were required to say 'seen' if they had detected the cue stimulus or 'not seen' if they missed it (self-report). 'Seen' and 'not seen' electroencephalographic trials were averaged separately to form visual evoked potentials. Sources of these potentials were estimated by LORETA software. Reaction time to go stimuli was shorter during spatially congruent than incongruent 'seen' trials, possibly due to covert attention on cue for self-report. It was also shorter during spatially congruent than incongruent 'not seen' trials, as an objective sign of unconscious processes. Cue stimulus evoked parieto-occipital potentials which has the same peak latencies in the 'seen' and 'not seen' cases. Sources of these potentials were located in occipital area 19 and parietal area 7. Source strength was significantly stronger in 'seen' than 'not seen' cases at approximately +300 ms post-stimulus. These results may unveil features of parieto-occipital activation accompanying visuo-spatial consciousness.

Adult↗

PubMed2005

Alpha rhythms in mild dements during visual delayed choice reaction time tasks: a MEG study.

Can simple delayed response tasks affect latency and amplitude of magnetoencephalographic midline alpha rhythms (6-12 Hz) in early dementia? We recruited 15 mild Alzheimer's disease (AD) and 10 vascular dementia (VaD) patients (paired mini mental state exam of 17-24). The control groups comprised 18 young and 22 elderly normal subjects. In the first task, a simple "cue" stimulus (one bit) was memorized along a brief delay period (3.5-5.5s) up to a "go" stimulus triggering (right or left) button press. In the second task, the "cue" stimulus remained available along the delay period. Event-related reduction in power of the alpha rhythms indexed the cortical activation (event-related desynchronization, ERD) for the trials associated with correct behavioral responses. Behavioral performances to both tasks were lower in the AD and VaD patients than in the normal subjects. In particular, just four AD and five VaD patients executed a sufficient amount of correct responses for the alpha ERD analysis, so they were included in a unique group. In both tasks, the alpha ERD peak was later in latency in the demented and normal elderly subjects than in the normal young subjects. Furthermore, the alpha ERD peak was stronger in amplitude in the demented patients than in the normal subjects. These results suggest that simple delayed response tasks during physiological recordings are quite difficult for patients even at an early dementia stage. Such difficulty may induce the abnormal amount of the related cortical activation in dementia as revealed by the alpha ERD.

Adolescent↗

PubMed2005

Right hemisphere specialization for intensity discrimination of musical and speech sounds.

Sound intensity is the primary and most elementary feature of auditory signals. Its discrimination plays a fundamental role in different behaviours related to auditory perception such as sound source localization, motion detection, and recognition of speech sounds. This study was aimed at investigating hemispheric asymmetries for processing intensity of complex tones and consonant-vowel syllables. Forty-four right-handed non-musicians were presented with two dichotic matching-to-sample tests with focused attention: one with complex tones of different intensities (musical test) and the other with consonant-vowel syllables of different intensities (speech test). Intensity differences (60, 70, and 80 dBA) were obtained by altering the gain of a synthesized harmonic tone (260 Hz fundamental frequency) and of a consonant-vowel syllable (/ba/) recorded from a natural voice. Dependent variables were accuracy and reaction time. Results showed a significant clear-cut left ear advantage in both tests for both dependent variables. A monaural control experiment ruled out possible attentional biases. This study provides behavioural evidence of a right hemisphere specialization for the perception of the intensity of musical and speech sounds in healthy subjects.

Adult↗

PubMed2005

Antero-posterior functional coupling at sleep onset: changes as a function of increased sleep pressure.

The use of the directed transfer function (DTF), an advanced computational analysis of electroencephalogaphic (EEG) data, which provides an estimation of the direction of the information flow underlying cortico-cortical functional coupling, has shown that the presleep period is characterized by posterior-to-anterior functional cortical coupling, while at sleep onset there is an inversion of that direction. This finding supported the idea that anterior cortical areas first synchronize sleep EEG activity. The aim of the present study was to assess the changes of functional coupling between anterior and posterior midline cortical areas during the sleep onset process when sleep pressure is heightened by a selective slow-wave sleep (SWS) deprivation. The hypothesis was that the anterior-to-posterior direction of the cortical functional coupling at sleep onset is enhanced by SWS deprivation. Ten normal right-handed male students slept for six consecutive nights in the laboratory (1: adaptation, 2: baseline, 3: baseline with awakenings, 4 and 5: SWS deprivations, 6: recovery), with standard polysomnographic recordings. The DTF was computed on data recorded during nights two and six from anterior (Fz(A1)) and posterior (Pz(A1), Oz(A1)) derivations. Results showed that, during the recovery night, the anterior-to-posterior direction of functional cortical coupling is already present in the presleep period, indicating that SWS deprivation advances the shift to an anterior-to-posterior directionality of functional cortical coupling, possibly as a consequence of heightened sleep pressure. These findings support the notion that a spread of synchronizing signals from associative prefrontal to posterior areas play a role in the wake-sleep transition.

Adult↗

PubMed2005

Stroop interference task and single-photon emission tomography in anorexia: a preliminary report.

OBJECTIVE: The aim of this preliminary study was to investigate the physiologic substrate of executive function in anorexia nervosa (AN) by assessing the relation between brain perfusion and Stroop interference task (SIT). METHOD: The classical SIT test and brain single-photon emission tomography (SPET) were evaluated in 16 AN females (mean age = 23.69 +/- 8.68 years; mean body mass index [BMI] = 16.19 +/- 1.53 kg/m2). The relation between the two examinations was searched by statistical parametric mapping (SPM 99) with a height threshold of p = .001. RESULTS: An abnormally low or a borderline SIT value was found in 25% of patients. A significant correlation between the SIT score and brain perfusion was found in the superior frontal gyrus of both hemispheres (Brodmann's area [BA] 6 in both hemispheres and BA 8 in the right hemisphere). No correlation was found in the anterior cingulate gyrus. CONCLUSION: BA 6 and BA 8 and the anterior cingulate are believed to be the basis of both error detection and immediate correction. Activity of BA 6 and BA 8 reflects this executive task in AN patients as well, whereas the lack of correlation in the anterior cingulate may suggest its blunted activity in AN patients, similarly to what is shown in other conditions characterized by impaired executive function, such as patients with depression, patients with schizophrenia, and abstinent drug abusers. However, these findings should still be quoted as preliminary, given some limitations of the study design, such as the lack of a control group, and the unfeasibility of controlling some relevant confounding variables, such as psychiatric comorbidity, medication, and the time interval between examinations, mainly deriving from the relatively few patients studied.

Adolescent↗

PubMed2005

Human alpha rhythms during visual delayed choice reaction time tasks: a magnetoencephalography study.

Magnetoencephalography (MEG) includes fast and comfortable recording procedures very suitable for the neurophysiological study of cognitive functions in aged people. In this exploratory MEG study in normal young adults, we tested whether very simple short-term memory (STM) demands induce visible changes in amplitude and latency of surface alpha rhythms. Two delayed response tasks were used. In the STM condition, a simple cue stimulus (one bit) was memorized along a brief delay period (3.5-5.5 s). In the control (no short-term memory; NSTM) condition, the cue stimulus remained available along the delay period. To make extremely simple the tasks, the explicit demand was visuospatial but the retention could be also based on phonological and somatomotor coding. Compared to the control condition, the amplitude of the alpha 1 (6-8 Hz) ERD decreased in the left hemisphere, whereas the amplitude of the alpha 2 (8-10 Hz) and alpha 3 (10-12 Hz) event-related desynchronization (ERD) increased in right and left parietal areas, respectively. Furthermore, the latency of the alpha ERD peak was slightly but significantly (P < 0.05) later in STM compared to control condition. In conclusion, whole-head MEG technology and very simple STM demands revealed significant changes of human neuromagnetic alpha rhythms in normal young adults.

Adult↗

PubMed2005

Contingent negative variation in the parasylvian cortex increases during expectancy of painful sensorimotor events: a magnetoencephalographic study.

Previous evidence relating to somatosensory-evoked magnetic fields has shown that the human parasylvian cortex (PC) is affected by ongoing painful sensorimotor interactions. In the present magnetoencephalographic study, the activity of the PC was investigated to evaluate the hypothesis of anticipatory processes preceding painful sensorimotor interactions. Sensorimotor interactions were induced by warned painful electrical stimulations at the left hand concomitant with a motor task of the right hand. The anticipatory activity of the PC was probed via contingent negative variation. Compared with the control nonpainful condition, the anticipation of the painful sensorimotor interactions increased the PC activity over the hemisphere ipsilateral to the stimulation. Dipole modeling indicated that the center of gravity of the anticipatory activity in the PC was located in the secondary somatosensory cortex. These results suggest that anticipation of painful sensorimotor interactions engages the human PC, especially in the hemisphere ipsilateral to upcoming painful stimuli and contralateral to preparatory motor commands.

Adult↗

PubMed2005

Expectancy of pain is influenced by motor preparation: a high-resolution EEG study of cortical alpha rhythms.

This high-resolution electroencephalographic (EEG) study on alpha event-related desynchronization (ERD) evaluated whether anticipatory activity precedes a sensorimotor interaction induced by concomitant painful stimuli and sensorimotor demand. An omitted-stimulus paradigm induced the expectancy of the painful stimulation at the left hand. In the experimental condition, the painful stimulation was associated with a visual go/no-go task triggering right-hand movements. Two control conditions manipulated the painful sensorimotor interaction variable. Compared with the control conditions, the expectancy of the painful sensorimotor interaction increased the high-band alpha EEG oscillations over the right primary sensorimotor cortex contralateral to the nociceptive stimuli and, to a lesser extent, over the centroparietal midline. These findings suggest that concomitant painful stimuli and simple sensorimotor go/no-go demands affect anticipatory activity as revealed by alpha ERD.

Adult↗

PubMed2005

Estimation of the cortical connectivity by high-resolution EEG and structural equation modeling: simulations and application to finger tapping data.

Today, the concept of brain connectivity plays a central role in the neuroscience. While functional connectivity is defined as the temporal coherence between the activities of different brain areas, the effective connectivity is defined as the simplest brain circuit that would produce the same temporal relationship as observed experimentally between cortical sites. The most used method to estimate effective connectivity in neuroscience is the structural equation modeling (SEM), typically used on data related to the brain hemodynamic behavior. However, the use of hemodynamic measures limits the temporal resolution on which the brain process can be followed. The present research proposes the use of the SEM approach on the cortical waveforms estimated from the high-resolution EEG data, which exhibits a good spatial resolution and a higher temporal resolution than hemodynamic measures. We performed a simulation study, in which different main factors were systematically manipulated in the generation of test signals, and the errors in the estimated connectivity were evaluated by the analysis of variance (ANOVA). Such factors were the signal-to-noise ratio and the duration of the simulated cortical activity. Since SEM technique is based on the use of a model formulated on the basis of anatomical and physiological constraints, different experimental conditions were analyzed, in order to evaluate the effect of errors made in the a priori model formulation on its performances. The feasibility of the proposed approach has been shown in a human study using high-resolution EEG recordings related to finger tapping movements.

Algorithms↗

PubMed2004

Age-related functional changes of prefrontal cortex in long-term memory: a repetitive transcranial magnetic stimulation study.

Neuroimaging findings suggest that the lateralization of prefrontal cortex activation associated with episodic memory performance is reduced by aging. It is still a matter of debate whether this loss of asymmetry during encoding and retrieval reflects compensatory mechanisms or de-differentiation processes. We addressed this issue by the transient interference produced by repetitive transcranial magnetic stimulation (rTMS), which directly assesses causal relationships between performance and stimulated regions. We compared the effects of rTMS (a rapid-rate train occurring simultaneously to the presentation of memoranda) applied to the left or right dorsolateral prefrontal cortex (DLPFC) on visuospatial recognition memory in 66 healthy subjects divided in two classes of age (<45 and >50 years). In young subjects, rTMS of the right DLPFC interfered with retrieval more than left DLPFC stimulation. The asymmetry of the effect progressively vanished with aging, as indicated by bilateral interference effects on recognition performance. Conversely, the predominance of left DLPFC effect during encoding was not abolished in elders, thus probing its causal role for encoding along the life span. Findings confirm that the neural correlates of retrieval modify along aging, suggesting that the bilateral engagement of the DLPFC has a compensatory role on the elders' episodic memory performance.

Adult↗

PubMed2004

Human cortical rhythms during visual delayed choice reaction time tasks. A high-resolution EEG study on normal aging.

Neuroimaging cognitive study of aging requires simple tasks ensuring a high rate of correct performances even in stressful neurophysiological settings. Here two simple delayed choice reaction time tasks were used to unveil event-related desynchronization (ERD) of theta (4-6 Hz) and alpha (6-12 Hz) electroencephalographic rhythms across normal aging. In the first condition, a cue stimulus (one bit) was memorized along a brief delay period (3.5-5.5 s). The explicit demand was visuo-spatial, but the retention could be also based on phonological and somatomotor coding. In the second condition, the cue stimulus remained available along the delay period. Correct performances were higher than 95% in both groups and tasks, although they were significantly better in young than elderly subjects (P < 0.03). During the delay period, theta and alpha ERD accompanying correct responses were recognized in the two groups, the alpha ERD being stronger and prolonged during the memory than non-memory task. On the other hand, the fronto-parietal theta and parietal alpha ERD were stronger in young than elderly subjects during both tasks. Notably, the frontal alpha ERD was negligible in elderly subjects. In conclusion, the present simple tasks unveiled in elderly compared to young subjects (i) a weaker involvement of (para)hippocampal-cortical circuits as revealed by theta ERD and (ii) a weaker involvement of "executive" thalamo-cortical circuits as revealed by frontal alpha ERD. These effects might worsen behavioral performances to the simple cognitive tasks with age. The present protocol is promising for the neuroimaging study of pathological aging.

Adult↗

PubMed2004

District-related frequency specificity in hand cortical representation: dynamics of regional activation and intra-regional synchronization.

The aim of this work was to study the degree of neuronal synchronization occurring within the portion of the somatosensory cortex devoted to hand control during an external sensory stimulation. In this way, we focused on the properties of the sensory cortical representation, rather than the more investigated motor one. To this aim, we collected magnetoencephalograhic data from healthy subjects during separate stimulation of their thumbs and little fingers and analyzed these data by means of a time-dependent 'synchronization index'. The properties of this index within the beta [16-32 Hz] and gamma [36-44 Hz] frequency bands suggest that the hand representation in the human primary cortex follows a frequency coding, in addition to the somatotopic one, for discriminating different districts. Our results showed that the gamma synchronization is higher following stimulation of the thumb than of the little finger and we suggest that the strength of gamma band synchronization works as a code for functional prevalence. In particular, our comparative analysis of the dynamic synchronization index and the signal amplitude suggests that a prevalent district (thumb) recruits a smaller number of higher-synchronic gamma band tuned neurons than a non-prevalent district (little finger).

Adult↗

PubMed2004

Attentional processes and cognitive performance during expectancy of painful galvanic stimulations: a high-resolution EEG study.

In the present high-resolution electroencephalographic (EEG) study, an omitted-stimulus paradigm induced a strong expectancy for a predictable painful stimulation (nonpainful in the control condition). During the expectancy of pain, concurrent cognitive demands were superimposed. The aim was to investigate the effects on primary sensorimotor and central midline areas of the competition among concurrent attentional processes related to cognition and pain expectancy, as indexed by behavioral performance and EEG data. A main issue was whether cognitive performance decreases, due to a re-allocation of attentional resources on primary sensorimotor and midline areas for the anticipation of pain. Behavioral results showed no differences in the cognitive (working memory) performance during the expectancy of nonpainful versus painful stimulations. In parallel, anticipatory event-related potentials (ERPs) were negligible in line with a low emotional reactivity/alertness as revealed by heart rate deceleration (HRD), skin conductance response (SCR), and low-band (6-10Hz) alpha EEG oscillations. In contrast, high-band alpha EEG oscillations (10-12Hz) over the contralateral primary sensorimotor cortex decreased more during the expectancy of painful compared to nonpainful stimuli, in line with an increased anticipatory preparation of the somatosensory channel. These findings provide further evidence on the fact that attentional processes at the basis of cognition can be defended by the anticipation of pain, at least when the incoming painful stimuli are repetitive and predictable. This happens even if the brain increases preparatory processes of the specific sensory channel to be targeted by the painful stimulus.

Adult↗

PubMed2004

Multimodal integration of EEG and MEG data: a simulation study with variable signal-to-noise ratio and number of sensors.

Previous simulation studies have stressed the importance of the multimodal integration of electroencephalography (EEG) and magnetoencephalography (MEG) data in the estimation of cortical current density. In such studies, no systematic variations of the signal-to-noise ratio (SNR) and of the number of sensors were explicitly taken into account in the estimation process. We investigated effects of variable SNR and number of sensors on the accuracy of current density estimate by using multimodal EEG and MEG data. This was done by using as the dependent variable both the correlation coefficient (CC) and the relative error (RE) between imposed and estimated waveforms at the level of cortical region of interests (ROI). A realistic head and cortical surface model was used. Factors used in the simulations were: (1). the SNR of the simulated scalp data (with seven levels: infinite, 30, 20, 10, 5, 3, 1); (2). the particular inverse operator used to estimate the cortical source activity from the simulated scalp data (INVERSE, with two levels, including minimum norm and weighted minimum norm); and (3). the number of EEG or MEG sensors employed in the analysis (SENSORS, with three levels: 128, 61, 29 for EEG and 153, 61, or 38 in MEG). Analysis of variance demonstrated that all the considered factors significantly affect the CC and the RE indexes. Combined EEG-MEG data produced statistically significant lower RE and higher CC in source current density reconstructions compared to that estimated by the EEG and MEG data considered separately. These observations hold for the range of SNR values presented by the analyzed data. The superiority of current density estimation by multimodal integration of EEG and MEG was not due to differences in number of sensors between unimodal (EEG, MEG) and combined (EEG-MEG) inverse estimates. In fact, the current density estimate relative to the EEG-MEG multimodal integration involved 61 EEG plus 63 MEG sensors, whereas estimations carried out with the single modalities alone involved 128 sensors for EEG and 153 sensors for MEG. The results of the simulations also suggest that the use of simultaneous 29 EEG sensors during the MEG measurements carried out with full sensor arrangements (153 sensors) returned an accuracy of the cortical source estimate statistically similar to that obtained by combining 64 EEG and 153 MEG sensors.

Brain↗

PubMed2004

Sub-second "temporal attention" modulates alpha rhythms. A high-resolution EEG study.

In the present high-resolution electroencephalographic (EEG) study, event-related desynchronization/synchronization (ERD/ERS) of alpha rhythms was computed during an S1-S2 paradigm, in which a visual cue (S1) predicted a SHORT (600 ms) or LONG (1400 ms) foreperiod, preceding a visual go stimulus (S2) triggering right or left finger movement. Could orienting attention to a selective point in time influence the alpha rhythms as a function of the SHORT vs. LONG foreperiod? Stronger selective attentional modulations were predicted for the SHORT than LONG condition. EEG data from 54 channels were "depurated" from phase-locked visual evoked potentials and spatially enhanced by surface Laplacian estimation (i.e., final data analysis was conducted on 16 subjects having a sufficient number of artifact-free EEG single trials). Low-band alpha rhythms (about 6-10 Hz) were supposed to be related to anticipatory attentional processes, whereas high-band alpha rhythms (10-12 Hz) would indicate task-specific visuo-motor processes. Compared to the LONG condition (foreperiod), the SHORT condition induced a quicker and stronger ERS at low-band alpha rhythm (about 6-8 Hz) over midline and bilateral prefrontal, sensorimotor, and posterior parietal areas. In contrast, the concomitant high-band alpha (about 10-12 Hz) ERD/ERS showed no significant difference between the two conditions. In conclusion, temporal attention for a sub-second delay (800 ms) did modulate low-band alpha rhythm over large regions of both cortical hemispheres.

Adolescent↗

PubMed2004

Estimation of the effective and functional human cortical connectivity with structural equation modeling and directed transfer function applied to high-resolution EEG.

Different brain imaging devices are presently available to provide images of the human functional cortical activity, based on hemodynamic, metabolic or electromagnetic measurements. However, static images of brain regions activated during particular tasks do not convey the information of how these regions are interconnected. The concept of brain connectivity plays a central role in the neuroscience, and different definitions of connectivity, functional and effective, have been adopted in literature. While the functional connectivity is defined as the temporal coherence among the activities of different brain areas, the effective connectivity is defined as the simplest brain circuit that would produce the same temporal relationship as observed experimentally among cortical sites. The structural equation modeling (SEM) is the most used method to estimate effective connectivity in neuroscience, and its typical application is on data related to brain hemodynamic behavior tested by functional magnetic resonance imaging (fMRI), whereas the directed transfer function (DTF) method is a frequency-domain approach based on both a multivariate autoregressive (MVAR) modeling of time series and on the concept of Granger causality. This study presents advanced methods for the estimation of cortical connectivity by applying SEM and DTF on the cortical signals estimated from high-resolution electroencephalography (EEG) recordings, since these signals exhibit a higher spatial resolution than conventional cerebral electromagnetic measures. To estimate correctly the cortical signals, we used a subject's multicompartment head model (scalp, skull, dura mater, cortex) constructed from individual MRI, a distributed source model and a regularized linear inverse source estimates of cortical current density. Before the application of SEM and DTF methodology to the cortical waveforms estimated from high-resolution EEG data, we performed a simulation study, in which different main factors (signal-to-noise ratio, SNR, and simulated cortical activity duration, LENGTH) were systematically manipulated in the generation of test signals, and the errors in the estimated connectivity were evaluated by the analysis of variance (ANOVA). The statistical analysis returned that during simulations, both SEM and DTF estimators were able to correctly estimate the imposed connectivity patterns under reasonable operative conditions, that is, when data exhibit an SNR of at least 3 and a LENGTH of at least 75 s of nonconsecutive EEG recordings at 64 Hz of sampling rate. Hence, effective and functional connectivity patterns of cortical activity can be effectively estimated under general conditions met in any practical EEG recordings, by combining high-resolution EEG techniques and linear inverse estimation with SEM or DTF methods. We conclude that the estimation of cortical connectivity can be performed not only with hemodynamic measurements, but also with EEG signals treated with advanced computational techniques.

Adult↗

PubMed2004

Multimodal integration of EEG, MEG and fMRI data for the solution of the neuroimage puzzle.

In 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 regularized linear inverse source estimates of cortical current density. Determination of the priors in the resolution of the linear inverse problem was performed 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.

Algorithms↗