Paolo Onorati

High resolution EEG: A new model-dependent spatial deblurring method using a realistically-shaped MR-constructed subject's head model

This paper presents a new model-dependent method for the spatial deblurring of scalp-recorded EEG potentials based on boundary-element and cortical imaging techniques. This model-dependent spatial deblurring (MDSD) method used MR images for the reconstruction of the subjects head model, and a layer of 364 radially-oriented equivalent current dipoles as a source model. The validation of the MDSD method was performed on simulated potential distributions generated from equivalent dipoles oriented radially, obliquely, and tangentially to the head surface. Furthermore, this method was used to localize neocortical sources of human movement-related and somatosensory-evoked potentials. It was shown that the new MDSD method improved markedly the spatial resolution of the simulated surface potentials and scalp-recorded event-related potentials. The spatial information content of the scalp-recorded EEG potentials increased progressively by increasing the spatial sampling from 28 to 128 channels. These results indicate that the new method could be satisfactorily used for high resolution EEG studies.

Performances of surface Laplacian estimators: A study of simulated and real scalp potential distributions

SummaryThis paper presents a study of the performance of various local and spherical spline methods currently in use for the surface Laplacian (SL) estimate of scalp potential distributions. The SL was estimated from simulated instantaneous event-related scalp potentials generated over a three-shell spherical head model. Laplacian estimators used planar and spherical scalp models. Noise of increasing magnitude and spatial frequency was added to the potential distributions in order to simulate noise presumed to contaminate scalp-recorded event-related potentials. A comparison of noise effects on various Laplacian estimates was made for increasing number of “electrode” positions in variants of the 10–20 system. Furthermore, to evaluate the error due to the use of unrealistic scalp models, the matching between SL estimates of human scalp-recorded movement-related potentials computed on spherical and realistically-shaped MRI-constructed models of the scalp was examined. With all methods the error of the SL estimate increased proportionally with the magnitude and spatial frequency of noise. Increased number of “electrodes” up to 256 significantly reduced the error (p<0.05). In general, the best SL estimates were computed by second and third order splines including λ correction, the performances of the second order spline being better with more than 64 “electrodes”. Compared with spline Lapladans, the best local methods provided nearly equal estimates with low spatial sampling (19 and 28 “electrodes”), as well as high spatial frequency noise. The error of the SL estimate due to unrealistic scalp model was significant, and it augmented with increased spatial sampling from 64 to 128 electrodes.

Early coding of reaching: frontal and parietal association connections of parieto-occipital cortex.

The ipsilateral association connections of the cortex of the dorsal part of the rostral bank of the parieto‐occipital sulcus and of the adjoining posterior part of the superior parietal lobule were studied by using different retrograde flourescent tracers. Fluoro‐Ruby, Fast blue and Diamidino yellow were injected into visual area V6A, and dorso‐caudal (PMdc, F2) and dorso‐rostral (PMdr, F7) premotor cortex, respectively. The parietal area of injection had been previously characterized physiologically in behaving monkeys, through a variety of oculomotor and visuomanual tasks. Area V6A is mainly linked by reciprocal projections to parietal areas 7m, MIP (medial intraparietal) and PEa, and, to a lesser extent, to frontal areas PMdr (rostral dorsal premotor cortex, F7) and PMdc (F2). All these areas project to that part of the dorsocaudal premotor cortex that has a direct access to primary motor cortex. V6A is also connected to area F5 and, to a lesser extent, to 7a, ventral (VIP) and lateral (LIP) intraparietal areas. This pattern of association connections may explain the presence of visually‐related and eye‐position signals in premotor cortex, as well as the influence of information concerning arm position and movement direction on V6A neural activity. Area V6A emerges as a potential ‘early’ node of the distributed network underlying visually‐guided reaching. In this network, reciprocal association connections probably impose, through re‐entrant signalling, a recursive property to the operations leading to the composition of eye and hand motor commands.

Postural control in patients with Down syndrome

Purpose. To assess postural control in individuals with Down syndrome. Method. Sixty young adults with Down syndrome were assessed and compared to 10 non-handicapped young. The subjects were asked to stay on a force platform for 30 seconds. Postural control was evaluated in two conditions: open and closed eyes. The kinetic data carried out from the force platform (i.e., ground reaction forces and Center of Pression (COP) displacements) were both evaluated in time domain and in frequency domain. Results. Patients with Down syndrome are characterized by instable postural control. In particular the data evaluation in frequency domain underlined for Down syndrome subjects versus control group an increase in frequency oscillation both in anterior-posterior and in medio-lateral direction, that are confirmed in time domain analysis only for medio-lateral direction. In DS no changes are evident between eyes open and eyes closed condition. Conclusion. This study finds that subjects with Down syndrome included in this research demonstrate that deficits in postural control system that may provide a partial explanation for function balance problems that are common in these subjects.

Ictal heart rate increase precedes EEG discharge in drug-resistant mesial temporal lobe seizures

OBJECTIVE Heart rate (HR) changes, mainly tachycardia, are often observed during seizures originating from the temporal lobe. The aim of this study was to analyze the role of ictal HR changes in localizing both mesial and lateral temporal lobe epilepsy (TLE) in a group of 68 patients. The influence of the gender and the side of epilepsy on HR modulation was also evaluated. METHODS Ictal HR was recorded during prolonged Video-EEG monitoring performed in 68 patients affected by drug-resistant TLE during a non-invasive pre-surgical protocol. According to the electro-clinical correlation, obtained by video-EEG monitoring, one hundred-thirteen seizures (n=113) and one hundred-forty-four auras (n=144) were identified and included in the study. Furthermore, the electro-clinical correlation allowed the classification of all the epileptic events (seizures and auras) as having mesial or lateral origin, based on the temporal lobe seizure onset zone. Ictal HR was calculated with respect to the R-R waves, and assessed from 15 sec (s) before (T(- 15)) to 15 s after (T(+15)) the time of EEG seizure onset (T(0)). RESULTS We observed a high incidence (92%) of ictal HR increase in TLE seizures. When the ictal EEG indicated a seizure onset from the mesial temporal structures, the onset of ictal HR increase preceded by about 5 s the EEG ictal onset (SD+/-18.4), whereas the onset of HR increase coincided with the onset of EEG discharges (SD+/-14.8) when the ictal EEG indicated the onset of seizures from the lateral temporal structures. No significant differences were found between male and female patients; and between right and left TLE. CONCLUSIONS Our findings show that ictal HR increase, preceding the onset of the EEG discharge, is associated with ictal EEG seizure pattern defining temporal lobe seizures originating from the mesial temporal lobe structures; this association suggests that the HR changes may be coupled to the functional impairment of neural circuits involved in sympathetic cardiovascular regulation, in the mesial temporal lobe structures. Further studies investigating the relationship between intracranial EEG monitoring and ECG recording are worthwhile, to confirm our results and to give further indications on the pathogenesis of ictal HR abnormalities.

Use of exercise testing in the evaluation of interventional efficacy: an official ERS statement.

This document reviews 1) the measurement properties of commonly used exercise tests in patients with chronic respiratory diseases and 2) published studies on their utilty and/or evaluation obtained from MEDLINE and Cochrane Library searches between 1990 and March 2015. Exercise tests are reliable and consistently responsive to rehabilitative and pharmacological interventions. Thresholds for clinically important changes in performance are available for several tests. In pulmonary arterial hypertension, the 6-min walk test (6MWT), peak oxygen uptake and ventilation/carbon dioxide output indices appear to be the variables most responsive to vasodilators. While bronchodilators do not always show clinically relevant effects in chronic obstructive pulmonary disease, high-intensity constant work-rate (endurance) tests (CWRET) are considerably more responsive than incremental exercise tests and 6MWTs. High-intensity CWRETs need to be standardised to reduce interindividual variability. Additional physiological information and responsiveness can be obtained from isotime measurements, particularly of inspiratory capacity and dyspnoea. Less evidence is available for the endurance shuttle walk test. Although the incremental shuttle walk test and 6MWT are reliable and less expensive than cardiopulmonary exercise testing, two repetitions are needed at baseline. All exercise tests are safe when recommended precautions are followed, with evidence suggesting that no test is safer than others. A review of exercise testing to evaluate interventions aimed to improve exercise tolerance in respiratory patients http://ow.ly/U37mQ

Gating of human short-latency somatosensory evoked cortical responses during execution of movement. A high resolution electroencephalography study

The present study aimed at investigating gating of median nerve somatosensory evoked cortical responses (SECRs), estimated during executed continuous complex ipsilateral and contralateral sequential finger movements. SECRs were modeled with an advanced high resolution electroencephalography technology that dramatically improved spatial details of the scalp recorded somatosensory evoked potentials. Integration with magnetic resonance brain images allowed us to localize different SECRs within cortical areas. The working hypothesis was that the gating effects were time varying and could differently influence SECRs. Maximum statistically significant (p<0. 01) time-varying gating (magnitude reduction) of the short-latency SECRs modeled in the contralateral primary motor and somatosensory and supplementary motor areas was computed during the executed ipsilateral movement. The gating effects were stronger on the modeled SECRs peaking 30-45 ms (N30-P30, N32, P45-N45) than 20-26 ms (P20-N20, P22, N26) post-stimulus. Furthermore, the modeled SECRs peaking 30 ms post-stimulus (N30-P30) were significantly increased in magnitude during the executed contralateral movement. These results may delineate a distributed cortical sensorimotor system responsible for the gating effects on SECRs. This system would be able to modulate activity of SECR generators, based on the integration of afferent somatosensory inputs from the stimulated nerve with outputs related to the movement execution.

Responses of human primary sensorimotor and supplementary motor areas to internally triggered unilateral and simultaneous bilateral one-digit movements. A high-resolution EEG study.

We modelled the responses of human primary sensorimotor areas and supplementary motor area to simple, self‐initiated unilateral and simultaneous bilateral middle finger movements using a novel high‐resolution electroencephalography technology. The results support the view that these cortical motor areas are involved in parallel and present similar activity in the preparation, initiation, and execution of the contralateral and bilateral movements. Furthermore, the left primary sensorimotor area (dominant hemisphere) appears to be activated more than the right primary sensorimotor area during the preparation and performance of the ipsilateral movements.

Dynamic functional coupling of high resolution EEG potentials related to unilateral internally triggered one-digit movements

Between-electrode cross-covariances of delta (0-3 Hz)- and theta (4-7 Hz)-filtered high resolution EEG potentials related to preparation, initiation. and execution of human unilateral internally triggered one-digit movements were computed to investigate statistical dynamic coupling between these potentials. Significant (P < 0.05, Bonferroni-corrected) cross-covariances were calculated between electrodes of lateral and median scalp regions. For both delta- and theta-bandpassed potentials, covariance modeling indicated a shifting functional coupling between contralateral and ipsilateral frontal-central-parietal scalp regions and between these two regions and the median frontal-central scalp region from the preparation to the execution of the movement (P < 0.05). A maximum inward functional coupling of the contralateral with the ipsilateral frontal-central-parietal scalp region was modeled during the preparation and initiation of the movement, and a maximum outward functional coupling during the movement execution. Furthermore, for theta-bandpassed potentials, rapidly oscillating inward and outward relationships were modeled between the contralateral frontal-central-parietal scalp region and the median frontal-central scalp region across the preparation, initiation, and execution of the movement. We speculate that these cross-covariance relationships might reflect an oscillating dynamic functional coupling of primary sensorimotor and supplementary motor areas during the planning, starting, and performance of unilateral movement. The involvement of these cortical areas is supported by the observation that averaged spatially enhanced delta- and theta-bandpassed potentials were computed from the scalp regions where task-related electrical activation of primary sensorimotor areas and supplementary motor area was roughly represented.

Human cortical activity related to unilateral movements. A high resolution EEG study

IN the present study a modern high resolution electroencephalography (EEG) technique was used to investigate the dynamic functional topography of human cortical activity related to simple unilateral internally triggered finger movements. The sensorimotor area (M1- S1) contralateral to the movement as well as the supplementary motor area (SMA) and to a lesser extent the ipsilateral M1-S1 were active during the preparation and execution of these movements. These findings suggest that both hemispheres may cooperate in both planning and production of simple unilateral volitional acts.