Impact of the acquisition protocol on the sensitivity to demyelination and axonal loss of clinically feasible DWI techniques: a simulation study.

OBJECTIVE: To evaluate: (a) the specific effect that the demyelination and axonal loss have on the DW signal, and (b) the impact of the sequence parameters on the sensitivity to damage of two clinically feasible DWI techniques, i.e. DKI and NODDI. METHODS: We performed a Monte Carlo simulation of water diffusion inside a novel synthetic model of white matter in the presence of axonal loss and demyelination, with three compartments with permeable boundaries between them. We compared DKI and NODDI in their ability to detect and assess the damage, using several acquisition protocols. We used the F test statistic as an index of the sensitivity for each DWI parameter to axonal loss and demyelination, respectively. RESULTS: DKI parameters significantly changed with increasing axonal loss, but, in most cases, not with demyelination; all the NODDI parameters showed sensitivity to both the damage processes (at p < 0.01). However, the acquisition protocol strongly affected the sensitivity to damage of both the DKI and NODDI parameters and, especially for NODDI, the parameter absolute values also. DISCUSSION: This work is expected to impact future choices for investigating white matter microstructure in focusing on specific stages of the disease, and for selecting the appropriate experimental framework to obtain optimal data quality given the purpose of the experiment.

Visual Learning Induces Changes in Resting-State fMRI Multivariate Pattern of Information.

When measured with functional magnetic resonance imaging (fMRI) in the resting state (R-fMRI), spontaneous activity is correlated between brain regions that are anatomically and functionally related. Learning and/or task performance can induce modulation of the resting synchronization between brain regions. Moreover, at the neuronal level spontaneous brain activity can replay patterns evoked by a previously presented stimulus. Here we test whether visual learning/task performance can induce a change in the patterns of coded information in R-fMRI signals consistent with a role of spontaneous activity in representing task-relevant information. Human subjects underwent R-fMRI before and after perceptual learning on a novel visual shape orientation discrimination task. Task-evoked fMRI patterns to trained versus novel stimuli were recorded after learning was completed, and before the second R-fMRI session. Using multivariate pattern analysis on task-evoked signals, we found patterns in several cortical regions, as follows: visual cortex, V3/V3A/V7; within the default mode network, precuneus, and inferior parietal lobule; and, within the dorsal attention network, intraparietal sulcus, which discriminated between trained and novel visual stimuli. The accuracy of classification was strongly correlated with behavioral performance. Next, we measured multivariate patterns in R-fMRI signals before and after learning. The frequency and similarity of resting states representing the task/visual stimuli states increased post-learning in the same cortical regions recruited by the task. These findings support a representational role of spontaneous brain activity.

Combining Multi-Shell Diffusion with Conventional MRI Improves Molecular Diagnosis of Diffuse Gliomas with Deep Learning.

The WHO classification since 2016 confirms the importance of integrating molecular diagnosis for prognosis and treatment decisions of adult-type diffuse gliomas. This motivates the development of non-invasive diagnostic methods, in particular MRI, to predict molecular subtypes of gliomas before surgery. At present, this development has been focused on deep-learning (DL)-based predictive models, mainly with conventional MRI (cMRI), despite recent studies suggesting multi-shell diffusion MRI (dMRI) offers complementary information to cMRI for molecular subtyping. The aim of this work is to evaluate the potential benefit of combining cMRI and multi-shell dMRI in DL-based models. A model implemented with deep residual neural networks was chosen as an illustrative example. Using a dataset of 146 patients with gliomas (from grade 2 to 4), the model was trained and evaluated, with nested cross-validation, on pre-operative cMRI, multi-shell dMRI, and a combination of the two for the following classification tasks: (i) IDH-mutation; (ii) 1p/19q-codeletion; and (iii) three molecular subtypes according to WHO 2021. The results from a subset of 100 patients with lower grades gliomas (2 and 3 according to WHO 2016) demonstrated that combining cMRI and multi-shell dMRI enabled the best performance in predicting IDH mutation and 1p/19q codeletion, achieving an accuracy of 75 ± 9% in predicting the IDH-mutation status, higher than using cMRI and multi-shell dMRI separately (both 70 ± 7%). Similar findings were observed for predicting the 1p/19q-codeletion status, with the accuracy from combining cMRI and multi-shell dMRI (72 ± 4%) higher than from each modality used alone (cMRI: 65 ± 6%; multi-shell dMRI: 66 ± 9%). These findings remain when we considered all 146 patients for predicting the IDH status (combined: 81 ± 5% accuracy; cMRI: 74 ± 5%; multi-shell dMRI: 73 ± 6%) and for the diagnosis of the three molecular subtypes according to WHO 2021 (combined: 60 ± 5%; cMRI: 57 ± 8%; multi-shell dMRI: 56 ± 7%). Together, these findings suggest that combining cMRI and multi-shell dMRI can offer higher accuracy than using each modality alone for predicting the IDH and 1p/19q status and in diagnosing the three molecular subtypes with DL-based models.

Analyzing the sensitivity of quantitative 3D MRI of longitudinal relaxation at very low field in Gd-doped phantoms.

PURPOSE: Recently, new MRI systems working at magnetic field below 10 mT (Very and Ultra Low Field regime) have been developed, showing improved T1-contrast in projected 2D maps (i.e. images without slice selection). Moving from projected 2D to 3D maps is not trivial due to the low SNR of such devices. This work aimed to demonstrate the ability and the sensitivity of a VLF-MRI scanner operating at 8.9 mT in quantitatively obtaining 3D longitudinal relaxation rate (R1) maps and distinguishing between voxels intensities. We used phantoms consisting of vessels doped with different Gadolinium (Gd)-based Contrast Agent (CA) concentrations, providing a set of various R1 values. As CA, we used a commercial compound (MultiHance®, gadobenate dimeglumine) routinely used in clinical MRI. METHODS: 3D R1 maps and T1-weighted MR images were analysed to identify each vessel. R1 maps were further processed by an automatic clustering analysis to evaluate the sensitivity at the single-voxel level. Results obtained at 8.9 mT were compared with commercial scanners operating at 0.2 T, 1.5 T, and 3 T. RESULTS: VLF R1 maps offered a higher sensitivity in distinguishing the different CA concentrations and an improved contrast compared to higher fields. Moreover, the high sensitivity of 3D quantitative VLF-MRI allowed an effective clustering of the 3D map values, assessing their reliability at the single voxel level. Conversely, in all fields, T1-weighted images were less reliable, even at higher CA concentrations. CONCLUSION: In summary, with few excitations and an isotropic voxel size of 3 mm, VLF-MRI 3D quantitative mapping showed a sensitivity better than 2.7 s-1 corresponding to a concentration difference of 0.17 mM of MultiHance in copper sulfate doped water, and improved contrast compared to higher fields. Based on these results, future studies should characterize R1 contrast at VLF, also with other CA, in the living tissues.

Impaired sustained attention in euthymic bipolar disorder patients and non-affected relatives: an fMRI study.

OBJECTIVE: Behavioral deficits in sustained attention have been reported during both acute and euthymic phases of type I bipolar disorder (BD-I) and also in non-affected relatives of bipolar disorder (BD) patients. In particular, selective failure in target recognition was proposed as a potential trait marker for BD, but there are few studies exploring the neural correlates. The aim of the present study was to analyze the behavioral and functional magnetic resonance imaging (fMRI) response of euthymic BD-I patients and non-affected relatives during a sustained attention task. METHODS: Twenty-four euthymic BD-I patients, 22 non-affected first-degree relatives of BD-I subjects, and 24 matched controls underwent a continuous performance test (CPT) with two levels of difficulty during event-related fMRI scanning. RESULTS: Both patients and relatives showed a lower accuracy in target detection when compared to controls. The fMRI data analysis revealed between-group differences in several brain regions involved in sustained attention. During error in target recognition, both patients and relatives showed a larger activation in the bilateral insula and the posterior part of the middle cingulate cortex. By contrast, during correct target response, only patients failed to activate the right insula, whereas relatives showed an increased activation of the left insula and bilateral inferior parietal lobule - limited to the higher attention load - and an augmented deactivation of the posterior cingulate/retrosplenial cortex. CONCLUSIONS: A selective impairment in target recognition during a CPT was behaviorally and functionally detectable in both euthymic BD-I patients and non-affected first-degree relatives, suggesting that specific sustained attention deficits may be a potential trait marker for BD-I.

The role of left superior parietal lobe in male sexual behavior: dynamics of distinct components revealed by FMRI.

INTRODUCTION: Despite the interest for the brain correlates of male sexual arousal, few studies investigated neural mechanisms underlying psychogenic erectile dysfunction (ED). Although these studies showed several brain regions active in ED patients during visual erotic stimulation, the dynamics of inhibition of sexual response is still unclear. AIM: This study investigated the dynamics of brain regions involved in the psychogenic ED. METHODS: Functional magnetic resonance imaging (fMRI) and simultaneous penile tumescence (PT) were used to study brain activity evoked in 17 outpatients with psychogenic ED and 19 healthy controls during visual erotic stimulation. Patterns of brain activation related to different phases of sexual response in the two groups were compared. MAIN OUTCOME MEASURES: Simultaneous recording of blood oxygen level-dependent fMRI responses and PT during visual erotic stimulation. RESULTS: During visual erotic stimuli, a larger activation was observed for the patient group in the left superior parietal lobe, ventromedial prefrontal cortex, and posterior cingulate cortex, whereas the control group showed larger activation in the right middle insula and dorsal anterior cingulate cortex and hippocampus. Moreover, the left superior parietal lobe showed a larger activation in patients than controls especially during the later stage of sexual response. CONCLUSION: Our results suggest that, among regions more active in patient group, the left superior parietal lobe plays a crucial role in inhibition of sexual response. Previous studies showed that left superior parietal lobe is involved in monitoring of internal body representation. The larger activation of this region in patients during later stages of sexual response suggests a high monitoring of the internal body representation, possibly affecting the behavioral response. These findings provide insight on brain mechanisms involved in psychogenic ED.

Neuroplasticity within and between Functional Brain Networks in Mental Training Based on Long-Term Meditation.

(1) The effects of intensive mental training based on meditation on the functional and structural organization of the human brain have been addressed by several neuroscientific studies. However, how large-scale connectivity patterns are affected by long-term practice of the main forms of meditation, Focused Attention (FA) and Open Monitoring (OM), as well as by aging, has not yet been elucidated. (2) Using functional Magnetic Resonance Imaging (fMRI) and multivariate pattern analysis, we investigated the impact of meditation expertise and age on functional connectivity patterns in large-scale brain networks during different meditation styles in long-term meditators. (3) The results show that fMRI connectivity patterns in multiple key brain networks can differentially predict the meditation expertise and age of long-term meditators. Expertise-predictive patterns are differently affected by FA and OM, while age-predictive patterns are not influenced by the meditation form. The FA meditation connectivity pattern modulated by expertise included nodes and connections implicated in focusing, sustaining and monitoring attention, while OM patterns included nodes associated with cognitive control and emotion regulation. (4) The study highlights a long-term effect of meditation practice on multivariate patterns of functional brain connectivity and suggests that meditation expertise is associated with specific neuroplastic changes in connectivity patterns within and between multiple brain networks.

Predicting Overall Survival Time in Glioblastoma Patients Using Gradient Boosting Machines Algorithm and Recursive Feature Elimination Technique.

Despite advances in tumor treatment, the inconsistent response is a major challenge among glioblastoma multiform (GBM) that lead to different survival time. Our aim was to integrate multimodal MRI with non-supervised and supervised machine learning methods to predict GBM patients' survival time. To this end, we identified different compartments of the tumor and extracted their features. Next, we applied Random Forest-Recursive Feature Elimination (RF-RFE) to identify the most relevant features to feed into a GBoost machine. This study included 29 GBM patients with known survival time. RF-RFE GBoost model was evaluated to assess the survival prediction performance using optimal features. Furthermore, overall survival (OS) was analyzed using univariate and multivariate Cox regression analyses, to evaluate the effect of ROIs and their features on survival. The results showed that a RF-RFE Gboost machine was able to predict survival time with 75% accuracy. The results also revealed that the rCBV in the low perfusion area was significantly different between groups and had the greatest effect size in terms of the rate of change of the response variable (survival time). In conclusion, not only integration of multi-modality MRI but also feature selection method can enhance the classifier performance.

Effects of somatosensory stimulation and attention on human somatosensory cortex: an fMRI study.

It is well known that primary and non-primary areas of human somatosensory cortex are involved in the processing of adequate deviant/rare stimuli and omission of frequent stimuli. However, the relative weight and interaction of these variables is poorly known. This functional magnetic resonance imaging (fMRI) study tested the hypothesis that somatosensory stimulus processing and attention especially interact in non-primary somatosensory areas including secondary somatosensory cortex (SII) and insula. To test this hypothesis, responses of somatosensory cortex were mapped during four conditions of an oddball paradigm: DELIVERED COUNT and IGNORE (count or ignore deviant/rare electrical stimuli, respectively); OMITTED COUNT and IGNORE (count or ignore the rare omission of frequent electrical stimuli, respectively). The deviant/rare and frequent electrical stimuli were delivered to median and ulnar nerve, respectively. It was observed that contralateral (left) primary somatosensory responses were not markedly modulated by the mentioned deviant/rare events. Furthermore, contralateral SII and insula responded to all but not OMITTED IGNORE (purely attentive) condition, whereas ipsilateral (right) SII responded to all conditions. Finally, ipsilateral insula responded to the COUNT (attentive) conditions, regardless of the physical presence of the deviant/rare stimuli. The results suggest that in somatosensory modality, bilateral SII and left (contralateral) insula reflect complex integrative processes of stimulus elaboration and attention, whereas right (ipsilateral) insula mainly sub-serves active attention to deviance within a sequence of somatosensory stimuli.

Altered brain response without behavioral attention deficits in healthy siblings of schizophrenic patients: an event-related fMRI study.

Attention deficits are common in schizophrenics and sometimes reported in their healthy relatives. The aim of this study was to analyse the behavioural performance and the brain activation of healthy siblings of schizophrenic patients during a sustained-attention task. Eleven healthy siblings of schizophrenic patients and eleven matched controls performed a Continuous Performance Test (CPT), during 1.5 T fMRI. The stimuli were presented at three difficulty-levels, using different degrees of degradation (0, 25 and 40%). There were no significant differences in CPT performance (mean reaction time and percentage of errors) between the two groups. Performance worsened with increasing degradation in both groups. Differences were found when comparing the BOLD signal change in the medial frontal gyrus/dorsal anterior cingulate, right precentral gyrus, bilateral posterior cingulate and bilateral insula. The most evident between group differences were observed in the left insula/inferior frontal gyrus: siblings showed a larger activation during wrong responses and a reduced activation during correct responses in the degraded runs. In conclusion, healthy siblings of schizophrenic patients showed differences in brain function in several brain regions previously reported in schizophrenic subjects, in the absence of behavioral attention deficits. The differences were greater in the two more difficult levels of attention demand and might be expressions of altered and/or compensatory mechanisms in subjects at increased risk for schizophrenia.

Large-scale brain networks account for sustained and transient activity during target detection.

Target detection paradigms have been widely applied in the study of human cognitive functions, particularly those associated with arousal, attention, stimulus processing and memory. In EEG recordings, the detection of task-relevant stimuli elicits the P300 component, a transient response with latency around 300 ms. The P300 response has been shown to be affected by the amount of mental effort and learning, as well as habituation. Furthermore, trial-by-trial variability of the P300 component has been associated with inter-stimulus interval, target-to-target interval or target probability; however, understanding the mechanisms underlying this variability is still an open question. In order to investigate whether it could be related to the distinct cortical networks in which coherent intrinsic activity is organized, and to understand the contribution of those networks to target detection processes, we carried out a simultaneous EEG-fMRI study, collecting data from 13 healthy subjects during a visual oddball task. We identified five large-scale networks, that largely overlap with the dorsal attention, the ventral attention, the core, the visual and the sensory-motor networks. Since the P300 component has been consistently associated with target detection, we concentrated on the first two brain networks, the time-course of which showed a modulation with the P300 response as detected in simultaneous EEG recordings. A trial-by-trial EEG-fMRI correlation approach revealed that they are involved in target detection with different functional roles: the ventral attention network, dedicated to revealing salient stimuli, was transiently activated by the occurrence of targets; the dorsal attention network, usually engaged during voluntary orienting, reflected sustained activity, possibly related to search for targets.

Toward a brain theory of meditation.

The rapidly progressing science of meditation has led to insights about the neural correlates of focused attention meditation (FAM), open monitoring meditation (OMM), compassion meditation (CM) and loving kindness meditation (LKM), in terms of states and traits. However, a unified theoretical understanding of the brain mechanisms involved in meditation-related functions, including mindfulness, is lacking. After reviewing the main forms of meditation and their relationships, the major brain networks and brain states, as well as influential theoretical views of consciousness, we outline a Brain Theory of Meditation (BTM). BTM takes the lead from considerations about the roles of the major brain networks, i.e., the central executive, salience and default mode networks, and their interplay, in meditation, and from an essential energetic limitation of the human brain, such that only up to 1% of the neurons in the cortex can be concurrently activated. The development of the theory is also guided by our neuroscientific studies with the outstanding participation of Theravada Buddhist monks, with other relevant findings in literature. BTM suggests mechanisms for the different forms of meditation, with the down-regulation of brain network activities in FAM, the gating and tuning of network coupling in OMM, and state-related up-regulation effects in CM and LKM. The theory also advances a leftward asymmetry in top-down regulation, and an enhanced inter-hemispheric integration, in meditation states and traits, also with implications for a theoretical understanding of conscious access. Meditation thus provides a meta-function for an efficient brain/mind regulation, and a flexible allocation of highly limited and often constrained (e.g., by negative emotion and mind wandering) brain activity resources, which can be related to mindfulness. Finally, a series of experimental predictions is derived from the theory.

Understanding brain connectivity from EEG data by identifying systems composed of interacting sources.

In understanding and modeling brain functioning by EEG/MEG, it is not only important to be able to identify active areas but also to understand interference among different areas. The EEG/MEG signals result from the superimposition of underlying brain source activities volume conducted through the head. The effects of volume conduction produce spurious interactions in the measured signals. It is fundamental to separate true source interactions from noise and to unmix the contribution of different systems composed by interacting sources in order to understand interference mechanisms. As a prerequisite, we consider the problem of unmixing the contribution of uncorrelated sources to a measured field. This problem is equivalent to the problem of unmixing the contribution of different uncorrelated compound systems composed by interacting sources. To this end, we develop a principal component analysis-based method, namely, the source principal component analysis (sPCA), which exploits the underlying assumption of orthogonality for sources, estimated from linear inverse methods, for the extraction of essential features in signal space. We then consider the problem of demixing the contribution of correlated sources that comprise each of the compound systems identified by using sPCA. While the sPCA orthogonality assumption is sufficient to separate uncorrelated systems, it cannot separate the individual components within each system. To address that problem, we introduce the Minimum Overlap Component Analysis (MOCA), employing a pure spatial criterion to unmix pairs of correlates (or coherent) sources. The proposed methods are tested in simulations and applied to EEG data from human micro and alpha rhythms.

Optimized 3D co-registration of ultra-low-field and high-field magnetic resonance images.

The prototypes of ultra-low-field (ULF) MRI scanners developed in recent years represent new, innovative, cost-effective and safer systems, which are suitable to be integrated in multi-modal (Magnetoencephalography and MRI) devices. Integrated ULF-MRI and MEG scanners could represent an ideal solution to obtain functional (MEG) and anatomical (ULF MRI) information in the same environment, without errors that may limit source reconstruction accuracy. However, the low resolution and signal-to-noise ratio (SNR) of ULF images, as well as their limited coverage, do not generally allow for the construction of an accurate individual volume conductor model suitable for MEG localization. Thus, for practical usage, a high-field (HF) MRI image is also acquired, and the HF-MRI images are co-registered to the ULF-MRI ones. We address here this issue through an optimized pipeline (SWIM-Sliding WIndow grouping supporting Mutual information). The co-registration is performed by an affine transformation, the parameters of which are estimated using Normalized Mutual Information as the cost function, and Adaptive Simulated Annealing as the minimization algorithm. The sub-voxel resolution of the ULF images is handled by a sliding-window approach applying multiple grouping strategies to down-sample HF MRI to the ULF-MRI resolution. The pipeline has been tested on phantom and real data from different ULF-MRI devices, and comparison with well-known toolboxes for fMRI analysis has been performed. Our pipeline always outperformed the fMRI toolboxes (FSL and SPM). The HF-ULF MRI co-registration obtained by means of our pipeline could lead to an effective integration of ULF MRI with MEG, with the aim of improving localization accuracy, but also to help exploit ULF MRI in tumor imaging.

A frontal but not parietal neural correlate of auditory consciousness.

Hemodynamic correlates of consciousness were investigated in humans during the presentation of a dichotic sequence inducing illusory auditory percepts with features analogous to visual multistability. The sequence consisted of a variation of the original stimulation eliciting the Deutsch's octave illusion, created to maintain a stable illusory percept long enough to allow the detection of the underlying hemodynamic activity using functional magnetic resonance imaging (fMRI). Two specular 500 ms dichotic stimuli (400 and 800 Hz) presented in alternation by means of earphones cause an illusory segregation of pitch and ear of origin which can yield up to four different auditory percepts per dichotic stimulus. Such percepts are maintained stable when one of the two dichotic stimuli is presented repeatedly for 6 s, immediately after the alternation. We observed hemodynamic activity specifically accompanying conscious experience of pitch in a bilateral network including the superior frontal gyrus (SFG, BA9 and BA10), medial frontal gyrus (BA6 and BA9), insula (BA13), and posterior lateral nucleus of the thalamus. Conscious experience of side (ear of origin) was instead specifically accompanied by bilateral activity in the MFG (BA6), STG (BA41), parahippocampal gyrus (BA28), and insula (BA13). These results suggest that the neural substrate of auditory consciousness, differently from that of visual consciousness, may rest upon a fronto-temporal rather than upon a fronto-parietal network. Moreover, they indicate that the neural correlates of consciousness depend on the specific features of the stimulus and suggest the SFG-MFG and the insula as important cortical nodes for auditory conscious experience.

Preferential coding of eye/hand motor actions in the human ventral occipito-temporal cortex.

The human ventral occipito-temporal cortex (OTC) contains areas specialized for particular perceptual/semantic categories, such as faces (fusiform face area, FFA) and places (parahippocampal place area, PPA). This organization has been interpreted as reflecting the visual structure of the world, i.e. perceptual similarity and/or eccentricity biases. However, recent functional magnetic resonance imaging (fMRI) studies have shown not only that regions of the OTC are modulated by non-visual, action-related object properties but also by motor planning and execution, although the functional role and specificity of this motor-related activity are still unclear. Here, through a reanalysis of previously published data, we tested whether the selectivity for perceptual/semantic categories in the OTC corresponds to a preference for particular motor actions. The results demonstrate for the first time that face- and place-selective regions of the OTC exhibit preferential BOLD response to the execution of hand pointing and saccadic eye movements, respectively. Moreover, multivariate analyses provide novel evidence for the consistency across neural representations of stimulus category and movement effector in OTC. According to a 'spatial hypothesis', this pattern of results originates from the match between the region eccentricity bias and the typical action space of the motor effectors. Alternatively, the double dissociation may be caused by the different effect produced by hand vs. eye movements on regions coding for body representation. Overall, the present findings offer novel insights on the coupling between visual and motor cortical representations.

Human cortical responses during one-bit delayed-response tasks: an fMRI study.

Neuroimaging study of cognition across aging requires simple tasks ensuring: (i) high rate of correct performances in neurophysiological settings; and (ii) significant modulation of cortical activity. As a preliminary step, the present functional magnetic resonance imaging (fMRI) study tested the hypothesis that very simple delayed-response tasks fit these requirements in normal young adults. The short-term memory (STM) variant included a sequence of cue stimulus (two vertical bars), delay period (blank screen for only 5s), go stimulus, and motor response compatible with the taller vertical bar. Noteworthy, the retention (only one bit) could be based on visuo-spatial, phonological, and somatomotor coding. In the control variant (no STM, NSTM), the cue stimulus was present during the delay period. Results showed high rate of correct performances in both tasks (about 95%). Compared to the NSTM task (delay period), the STM task enhanced cortical responses in bilateral dorsolateral prefrontal (Brodmann area 8-9 (BA 8-9)), lateral premotor (BA 6L), medial premotor (BA 6M), inferior parietal (BA 40), and superior parietal (BA 7) areas. In the STM task, cortical responses were stronger in right than left BA 8-9 and BA 6L. These results indicate that, in normal young adults, a simple STM variant of delayed-response tasks (one bit to be retained) is correctly performed and enhances bilateral fronto-parietal responses. Therefore, it may be used for future cognitive neuroimaging studies on aging.

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. Results replicated previous fMRI evidence. Right M1 and S1 were much more activated during left rather than right movements, whereas such a difference was less evident in left M1 and S1. A novel finding consisted in an analogous functional hemispherical asymmetry in left and right SMA. Strikingly, left SMA activation did not differ statistically during right (contralateral) vs. left (ipsilateral) movements. It was concluded that, in right-handed subjects, left SMA plays a prevailing role in the control of voluntary movements.

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. This review summarizes the physical principles, instrumentation, main clinical applications and perspectives for the clinical use of MCG. This second part is devoted to the description of the main current clinical applications and perspectives.

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. This review summarizes the physical principles, instrumentation, main clinical applications and perspectives for the clinical use of MCG. This first part is devoted to the description of the physical principles and instrumentation.