Hemispherical asymmetry in human SMA during voluntary simple unilateral movements. An fMRI study.

Functional magnetic resonance imaging (fMRI) was used to test the hypothesis of a prevailing role of left supplementary motor area (SMA) during voluntary right and left finger movements, in line with subjects' right hand preference. fMRI responses were quantified using task-related percent increase of the signal from statistically activated voxels in primary somatosensory (S1), primary motor (M1), and SMA cortical regions. Regional analysis comprised both extension and intensity of statistically activated groups of voxels.

Multimodal integration of high-resolution EEG and functional magnetic resonance imaging data: a simulation study.

Previous simulation studies have stressed the importance of the use of fMRI priors in the estimation of cortical current density. However, no systematic variations of signal-to-noise ratio (SNR) and number of electrodes were explicitly taken into account in the estimation process. In this simulation study we considered the utility of including information as estimated from fMRI.

Raynaud's phenomenon: Infrared functional imaging applied to diagnosis and drug effects.

A non-invasive, innovative approach to the study of Raynaud's Phenomenon is proposed. A group of patients, with respect of a control group, underwent a simultaneous assessment of thermal properties of all ten fingers using infrared functional imaging (IRFI). The assessment highlighted a quite different behaviour between patients with Primary- (PRP) and those with scleroderma - Raynaud's Phenomenon (SSc) and, compared with other existing techniques, seems to be an objective and effective tool to discriminate between PRP and RP secondary to SSc.

Cortical source estimate of combined high resolution EEG and fMRI data related to voluntary movements.

Objectives: In this paper, we employed advanced methods for the modeling of human cortical activity related to voluntary right one-digit movements from combined high-resolution electroencepholography (EEG) and functional magnetic resonance imaging (fMRI).

Methods: Multimodal integration between EEG and fMRI data was performed by using realistic head models, a large number of scalp electrodes (128) and the estimation of current density strengths by linear inverse estimation.

Results: Increasing of spatial details of the estimated cortical density distributions has been detected by using the proposed integration method with respect to the estimation using EEG data alone.

Topographic organization of the human primary and secondary somatosensory cortices: comparison of fMRI and MEG findings.

We studied MEG and fMRI responses to electric median and tibial nerve stimulation in five healthy volunteers. The aim was to compare the results with those of a previous study using only fMRI on the primary and secondary somatosensory cortices in which the somatotopic organization of SII was observed with fMRI. In the present work we focus on the comparison between fMRI activation and MEG equivalent current dipole (ECD) localizations in the SII area.

Comparison between SI and SII responses as a function of stimulus intensity.

In this MEG study we investigated the differences in responses to somatosensory electrical stimuli between primary (SI) and secondary (SII) sensory cortices using 10 different levels of stimulus intensity, starting from below the sensory threshold up to a weak painful level. SI dipole source linearly increased in amplitude as the stimulus intensity raised up to a strong motor level and then saturated at higher stimulation levels. The contralateral and ipsilateral SII dipole source strengths followed the stimulus intensity growing up to the motor threshold, but showed a decrease at the strong motor level, followed by an increase as the stimulus intensity raised towards the weak painful threshold.

Magnetocardiography: current status and perspectives. Part II: Clinical applications.

Magnetocardiography (MCG) is a non-invasive and risk-free technique allowing body surface recording of the magnetic fields generated by the electrical activity of the heart. The MCG recording system allows spatially and temporally accurate measurements of the very weak magnetic fields produced by currents flowing within myocardial fibers during cardiac activity. MCG has now been around for over 30 years, but only recently has progress in instrumentation put the technique on the verge of clinical applicability.

Magnetocardiography: current status and perspectives. Part I: Physical principles and instrumentation.

Magnetocardiography (MCG) is a non-invasive and risk-free technique allowing body surface recording of the magnetic fields generated by the electrical activity of the heart. The MCG recording system allows spatially and temporally accurate measurements of the very weak magnetic fields produced by currents flowing within myocardial fibers during cardiac activity. MCG has now been around for over 30 years, but only recently has progress in instrumentation put the technique on the verge of clinical applicability.

Somatosensory processing during movement observation in humans.

Objectives: A neural system matching action observation and execution seems to operate in the human brain, but its possible role in processing sensory inputs reaching the cortex during movement observation is unknown.

Methods: We investigated somatosensory evoked potentials (SEPs), somatosensory evoked fields (SEFs) and the temporal spectral evolution of the brain rhythms (approximately 10 and approximately 20 Hz) following electrical stimulation of the right median nerve in 15 healthy subjects, during the following randomly intermingled conditions: a pure cognitive/attentive task (mental calculation); the observation of a motoric act (repetitive grasping) with low cognitive content ('Obs-grasp'); and the observation of a complex motoric act (finger movement sequence), that the subject had to recognize later on, therefore reflecting an adjunctive cognitive task ('Obs-seq'). These conditions were compared with an absence of tasks ('Relax') and actual motor performance.

Linear inverse source estimate of combined EEG and MEG data related to voluntary movements.

A method for the modeling of human movement-related cortical activity from combined electroencephalography (EEG) and magnetoencephalography (MEG) data is proposed. This method includes a subject's multi-compartment head model (scalp, skull, dura mater, cortex) constructed from magnetic resonance images, multi-dipole source model, and a regularized linear inverse source estimate based on boundary element mathematics. Linear inverse source estimates of cortical activity were regularized by taking into account the covariance of background EG and MEG sensor noise.

Integration of high resolution EEG and functional magnetic resonance in the study of human movement-related potentials.

Cortical sources of human movement-related potentials (i.e. unilateral finger extension) were modeled using functional magnetic resonance imaging (fMR) data as a constraint of a linear inverse source estimation from highly sampled (128 channels) EEG data.

Topographic organization of the human primary and secondary somatosensory areas: an fMRI study.

The topographical organization of SI and SII somatosensory areas was investigated using fMRI at 1.5 T and electrical sensory stimulation. Electrical stimuli were delivered unilaterally to the median nerve at the wrist and to the tibial nerve at the medial malleolus, during a block paradigm study.

Morphology of somatosensory evoked fields: inter-hemispheric similarity as a parameter for physiological and pathological neural connectivity.

The morphology of somatosensory evoked fields (SEF) following electrical separate stimulation of left and right median nerve in 22 healthy volunteers was explored. The analysis of morphological properties of individual SEFs has been performed, in order to quantify an inter-hemispheric correlation coefficient. Despite a high inter-subject variability of the SEF morphologies, a high intra-subject inter-hemispheric shape correlation occurs in the post-stimulus epoch of 100 ms from the stimulus onset.

Tonotopic cortical changes following stapes substitution in otosclerotic patients: a magnetoencephalographic study.

The aim of the study was to investigate and follow up the tonotopic organization of the primary auditory cortex in otosclerotic patients before and after corrective surgery. The characteristics of primary auditory cortex activation were studied in ten otosclerotic patients (i.e.

Functional localization of the sensory hand area with respect to the motor central gyrus knob.

The aim of this work was to investigate the topography of the primary sensory hand cortex with magnetoencephalography in order to define the functional anatomy of this area in healthy humans. Previous studies denoted an inverted Ohm or an horizontal epsilon shaped knob on the pre-central gyrus as a landmark for the motor hand area; therefore a systematic difference between the orientation of the source for thumb with respect to little finger should be observed. We found this systematic difference, but the direction of the sources activated during thumb and little finger stimulation did not converge, as would be expected if only the Ohm convexity is activated: in fact our results suggest that thumb sensory area also extends to the area lateral to this convexity.

Bilateral neuromagnetic activation of human primary sensorimotor cortex in preparation and execution of unilateral voluntary finger movements.

Extracranial magnetoencephalographic activity was separately recorded (25 channels) from bilateral primary sensorimotor cortex (M1-S1) of normal right-handers during unilateral finger movements. Standard dipole analysis indicated only a contralateral M1-S1 source for first movement-evoked field (MEF1) peaking at about 115 ms after electromyographic onset. However, the subtraction of the magnetic field generated by this source from the recorded magnetic field disclosed a low-amplitude ipsilateral central-parietal MEF1 that was explained by an ipsilateral M1-S1 source.

The use of an inhomogeneous applied field improves the spatial sensitivity profile of an in vivo SQUID susceptometer.

We present a SQUID susceptometer with a non-homogeneous magnetizing field which is null at the sensing coil and increases towards the patient position with a constant gradient plus a cubic term at large distances. Compared with the magnetizing fields of similar instruments described in the literature, our gradient field enhances the signal due to internal organs with respect to the signal due to superficial tissue. Preliminary measurements have been performed on phantoms of known magnetic susceptibility.

Hand motor cortical area reorganization in stroke: a study with fMRI, MEG and TCS maps.

The anatomical and functional correlates of the hand sensorimotor areas was investigated in a stroke patient with a malacic lesion in the left fronto-parieto-temporal cortex. The patient presented hemiplegia and motor aphasia 12 months earlier, followed by an excellent motor recovery. Transcranial magnetic stimulation mapping, functional magnetic resonance and magnetoencephalography were used as methods of functional imaging and all yielded consistent results.

A neuromagnetic normative data set for hemispheric sensory hand cortical representations and their interhemispheric differences.

Somatotopy of human hand primary sensory cortex has been studied neuromagnetically [C. Baumgartner, A. Doppelbauer, L.

On the reorganization of sensory hand areas after mono-hemispheric lesion: a functional (MEG)/anatomical (MRI) integrative study.

The topography of primary sensory cortical hand area following a monohemispheric lesion (sudden = stroke; progressive = neoplasm) was investigated in relationship with clinical recovery of sensorimotor deficits. Twenty seven patients with monohemispheric lesions were studied in a clinically stabilized condition. Functional informations from magnetoencephalography (MEG) were integrated with anatomical data from magnetic resonance imaging (MRI).

Spatial properties and interhemispheric differences of the sensory hand cortical representation: a neuromagnetic study.

We performed a neuromagnetic investigation of the sensory hand cortical representation in the two hemispheres of 20 healthy volunteers. The localizations within the brain hemispheres of the cortical Equivalent Current Dipoles (ECDs) activated with the shortest latencies (N20 m and P30 m components) by separate stimulation of contralateral median nerve, thumb and little finger were analysed. The ECD spatial coordinates were in agreement with the known somatotopy of the sensory homunculus: little finger more medial and posterior, thumb more lateral and anterior, median nerve in-between.