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The synthetic aperture magnetometry (SAM) is a spatially selective beamformer, which transforms neuromagnetic signals into units of dipole moment on a per-voxel basis. We applied this technique to demonstrate the tomographic distribution of the power calculated from the spontaneous magnetoencephalogram (MEG) activities in a patient with a focal cerebral ischemia.The distribution of spontaneous MEG activity was affected by the changes in the regional cerebral blood flow (rCBF) and also by the presence of magnetic resonance image (MRI)-documented lesion. The present study for the first time demonstrated the altered patterns in the tomography of spontaneous MEG activity at different frequency bands, i.e. delta, alpha and beta bands, in a stroke patient which may elucidate an important implication in the pathoneurophysiology associated with cerebral ischemia. [Copyright &y& Elsevier]

Abstract: A brain machine interface (BMI) provides the possibility of controlling such external devices as prosthetic arms for patients with severe motor dysfunction using their own brain signals. However, there have been few studies investigating the decoding accuracy for multiclasses of useful unilateral upper limb movements using non-invasive measurements. We investigated the decoding accuracy for classifying three types of unilateral upper limb movements using single-trial magnetoencephalography (MEG) signals. Neuromagnetic activities were recorded in 9 healthy subjects performing 3 types of right upper limb movements: hand grasping, pinching, and elbow flexion. A support vector machine was used to classify the single-trial MEG signals. The movement types were predicted with an average accuracy of 66±10% (chance level: 33.3%) using neuromagnetic activity during a 400-ms interval (−200ms to 200ms from movement onsets). To explore the time-dependency of the decoding accuracy, we also examined the time course of decoding accuracy in 50-ms sliding windows from −500ms to 500ms. Decoding accuracies significantly increased and peaked once before (50.1±4.9%) and twice after (58.5±7.5% and 64.4±7.6%) movement onsets in all subjects. Significant variability in the decoding features in the first peak was evident in the channels over the parietal area and in the second and third peaks in the channels over the sensorimotor area. Our results indicate that the three types of unilateral upper limb movement can be inferred with high accuracy by detecting differences in movement-related brain activity in the parietal and sensorimotor areas. [Copyright &y& Elsevier]

Abstract: Alpha rhythm is one of the most prominent electromagnetic changes in the brain, and electroencephalography (EEG) alpha reactivity disturbance may sometimes represent an early sign of cerebral dysfunction. Although magnetoencephalography (MEG) has a better spatial resolution than EEG, it has not extensively been used to explore alpha-power change deficits in schizophrenia as a possible neurophysiological marker of the disease. The purpose of this study was to use MEG to identify abnormalities in alpha synchronization induced by eye-closing in schizophrenia patients compared to healthy controls, and to investigate whether alpha reactivity deficits correlate with clinical features of the disorder. MEG data were recorded in 22 schizophrenia patients and 20 age- and gender-matched controls during eyes-open/eyes-closed resting states. Cortical sources of event-related synchronization (ERS) were estimated using multiple source beamformer, and BrainVoyager was used for statistic group analysis. A significant decrease in ERS in the upper alpha band (10–13Hz) was found in the left posterior temporal region in schizophrenia patients relative to controls, and this activity showed correlation with visual memory scores. This upper alpha ERS deficit may indicate left temporal dysfunction and visual-information processing impairment in schizophrenia, and upon further confirmation it might represent a neurophysiological state marker of the disorder. [Copyright &y& Elsevier]

Abstract: The mu rhythm is regarded as a physiological indicator of the human mirror neuron system (MNS). The dysfunctional MNS hypothesis in patients with autistic spectrum disorder (ASD) has often been tested using EEG and MEG, targeting mu rhythm suppression during action observation/execution, although with controversial results. We explored neural activity related to the MNS in patients with ASD, focusing on power increase in the beta frequency band after observation and execution of movements, known as post-movement beta rebound (PMBR). Multiple source beamformer (MSBF) and BrainVoyager QX were used for MEG source imaging and statistical group analysis, respectively. Seven patients with ASD and ten normal subjects participated in this study. During the MEG recordings, the subjects were asked to observe and later execute object-related hand actions performed by an experimenter. We found that both groups exhibited pronounced PMBR exceeding 20% when observing and executing actions with a similar topographic distribution of maximal activity. However, significantly reduced PMBR was found only during the observation condition in the patients relative to controls in cortical regions within the MNS, namely the sensorimotor area, premotor cortex and superior temporal gyrus. Reduced PMBR during the observation condition was also found in the medial prefrontal cortex. These results support the notion of a dysfunctional execution/observation matching system related to MNS impairment in patients with ASD, and the feasibility of using MEG to detect neural activity, in particular PMBR abnormalities, as an index of MNS dysfunction during performance of motor or cognitive tasks. [Copyright &y& Elsevier]

Abstract: Situs inversus totalis (SI) is a rare condition in which all visceral organs are arranged as mirror images of the usual pattern. The objective of this study was to determine whether SI individuals have reversed brain asymmetries. We performed a neuroimaging study on 3 SI subjects and 11 control individuals with normally arranged visceral organs. The language-dominant hemisphere was determined by magnetoencephalography. Left-hemispheric dominance was observed in 1 SI subject and all controls, whereas right-hemispheric dominance was observed in the remaining 2 SI subjects. Statistical analysis revealed that language dominance patterns in SI subjects were different from those in the controls, suggesting that the developmental mechanisms underlying visceral organ asymmetries are related to those underlying functional brain asymmetry. Anatomical brain asymmetries were determined by magnetic resonance imaging. SI subjects had the same planum temporale (PT) asymmetry pattern as the controls, but a reversed petalia asymmetry pattern. The inferior frontal gyrus (IFG) asymmetry pattern varied within both groups, indicating a relationship between the rightward IFG and right-hemispheric language dominance. These results suggest that the developmental mechanisms underlying visceral organ asymmetries are related to those underlying petalia asymmetry but not to those underlying PT and IFG asymmetries, and that brain asymmetries might develop via multiple region-dependent mechanisms. [Copyright &y& Elsevier]

Abstract: In patients with Alzheimer''s disease (AD), it is sometimes challenging to identify typical findings in electroencephalography (EEG) or magnetoencephalography (MEG) such as a slowing of the posterior dominant activity or an increase in slow activity. In this MEG study, we evaluated the event-related synchronization (ERS) of alpha activity after eye closing in patients with early AD and mild cognitive impairment (MCI) who presented no slow MEG pattern. Thirteen patients with probable AD and thirteen patients with MCI, who met NINCDS-ADRDA and Petersen''s diagnostic criteria, respectively, were enrolled. We also selected fourteen age-matched normal control subjects. MEG activity was acquired during eye-open and eye-closed states. The ERS after eye closing within 8–15Hz frequency band was calculated and its cortical source was superimposed on the individual''s MRI by using the beamformer implemented in Brain Electrical Source Analysis (BESA). The Source image was converted into a standardized image, and group comparisons across patients with AD, MCI and controls were performed using BrainVoyager QX. The averaged ERS was observed dominantly in posterior regions in all three groups. Significant difference in ERS was observed only for the comparison between AD patients and controls, with AD patients showing increased ERS in frontal regions. Frontal shift of posterior alpha activity was observed clearly in AD patients using the combination of beamformer and group comparison. [Copyright &y& Elsevier]

Abstract: Synthetic aperture magnetometry (SAM) was applied to investigate changes in the mechanism of cerebral motor control in patients with tumors around the central sulcus in relation to the clinical relevance. MEG records were made during a resting state and a repetitive hand grasping task in patients with brain tumors around the central sulcus and in four control subjects. Topographic appearance of abnormal focal slowing in the delta, theta, and alpha bands (N =10) and event related desynchronizations (ERD) in the alpha, beta, and low gamma bands during the motor tasks (N =6) were analyzed statistically with SAM in relation to clinical signs and symptoms. Distribution of enhanced focal delta activity coincident with the motor cortices responsible for weakness. Volumetric analysis revealed emergence of tumor-related focal delta activity was greater for intra-axial tumors involving subcortical fibers than for other extra-axial tumors. In addition, patients with increased volume of enhanced delta activity exhibited poor functional recovery in the early post-operative period. Beta ERD in patients during affected side hand movement was also localized exclusively to the ipsilateral hemisphere contrary to the normal pattern. The characteristic focal delta distribution and the altered patterns of ERD in the patient group suggest not only close relation of cortical function and existing pathology but recruitment of diverse motor areas which may be required for the effective movement of the affected side. [Copyright &y& Elsevier]

Abstract: Cerebral occlusive vascular disease has been well investigated in aspect of a risk factor for stroke, however, whether it causes any alteration in brain function is poorly understood. To investigate this, we examined the motor related magnetic field in 20 patients with cerebral occlusive disease (12 with atherosclerotic (AS group) and 8 with non-atherosclerotic lesions (NAS group)) and 7 control subjects, and evaluated the spatial distribution and the intensity (t-value) of event related desynchronization in beta band during hand grasping and finger tapping tasks using synthetic aperture magnetometry. According to the laterality index (L.I.) calculated from peak t-values on both hemispheres, activation pattern was classified into 3 types, as contralateral—(L.I.>0), bilateral—(0.1

We examined transient neural activations from the input of a stimulus to the output of a response during the Stroop task for schizophrenic subjects with/without auditory hallucinations using a spatial filtered technique, synthetic aperture magnetometry (SAM), which provides high temporal and spatial resolution. MEG signals from the presentation of incongruent stimuli to responses were analyzed with a time window of 200 ms in steps of 50 ms. According to our previous studies with healthy subjects, regions showing significant decrease of current source density (CSD) in the 25–60-Hz band, corresponding to event-related desynchronization, were regarded to be activated. The non-hallucinators showed neural activations in the inferior parietal or temporal regions in the early stage of information processing, and successive and temporally overlapping neural activations in the left dorsolateral prefrontal cortex (DLPFC) and primary motor area (M1). The hallucinators showed neural activations in the right DLPFC and M1. Our preliminary results suggest that the schizophrenic subjects showed transient neural activations along the fundamental information flow (sensory input system–executive control system–motor output system), and that lateralization of DLPFC might be related with auditory hallucinations in schizophrenia. [Copyright &y& Elsevier]

Mu rhythm is the alpha (8–15 Hz) band oscillatory activity recorded over the sensorimotor cortex accompanied by a higher frequency band activity like beta (15–30 Hz) band. The contralateral sensorimotor area shows event-related desynchronization (ERD) of mu rhythm during limb movement and event-related synchronization (ERS) after the termination of the movement. Previous studies reported that ERD/ERS of mu and beta rhythm were detected during movement observation in the absence of physical movement, as well as during movement execution, suggesting that further investigations into the ERD/ERS of mu and beta rhythm in movement observation may elucidate the mechanisms of the mirror neuron system. We examined the post-movement ERS in beta band after movement observation by using MEG and Synthetic Aperture Magnetometry (SAM) analysis. The post-movement beta ERS was estimated over the bilateral, primary, sensorimotor area after the movement execution in all subjects, and estimated over the contralateral, primary, sensorimotor area after movement observation in four out of six subjects. Our results suggest that MEG SAM analysis is useful for the investigation of the mirror neuron system, which can be applied to clinical research for neurological and psychiatric diseases. [Copyright &y& Elsevier]

The aim of this study was to verify the relation between gamma-band activity and process of function words. We recorded the neuromagnetic signals in six healthy volunteers during silent reading of verbs (verb task) and forming of the past tenses (past-tense task) and investigated the spatio-temporal distribution of event-related desynchronization (ERD) and synchronization using synthetic aperture magnetometry. In both tasks, ERDs were observed simultaneously at multiple language-related areas. The left junctional area of inferior frontal sulcus and precentral sulcus and the left supramarginal gyrus showed stronger and/or longer-lasting ERDs in past-tense task than in verb task. This result suggests that the gamma-activities reflect the syntactic process of words. [Copyright &y& Elsevier]

Parallel distributed processing neuroimaging in the Stroop color word interference task in five healthy subjects was studied. The total reaction time was set at 650 ms with a time window of 200 ms in steps of 50 ms. Spatially filtered magnetoencephalography analysis, as used in synthetic aperture magnetometry, was used. Neural activation began in the left posterior parietal-occipital area (150–250 ms post-stimulus), followed by the right prefrontal polar area (250–350 ms), the left dorsolateral prefrontal cortex (250–400 ms), and the mid- to lower- primary motor area (350–400 ms). Successive and temporally overlapping activation of various cortical regions were successfully estimated within a short 200 ms time interval, contrary to previous positron emission tomography and fMRI studies. [Copyright &y& Elsevier]

Using synthetic aperture magnetometry (SAM), we examined the spatial distribution of frequency changes in magnetoencephalography signal rhythms on individual magnetic resonance images following somatosensory stimulation. SAM is a novel statistical spatial filtering method that uses an adaptive beamformer. Electrical stimulation of the right median nerve demonstrated high-frequency event-related synchronization (ERS) in the 50–200-Hz range, consistently localized in the contralateral primary sensorimotor area in all subjects (n=7). Event-related desynchronization (ERD) was demonstrated in the 8–13, 13–25 and 25–50-Hz ranges bilaterally in the area surrounding the central sulcus. The differences in the spatial distribution as well as the frequency bands between ERS and ERD suggest that ERS and ERD reflect the responses of different cell assemblies rather than a frequency shift of the same cell assembly. [Copyright &y& Elsevier]

Objectives Phantom limb pain is neuropathic pain after amputation of a limb and partial or complete deafferentation such as brachial plexus root avulsion. The underlying cause of this pain has been attributed to maladaptive plasticity of the sensorimotor cortex. It has been suggested that experimental reorganization would affect pain, especially if it results in functional restoration. We tested the hypothesis that restoration of hand motor function using a brain–machine interface (BMI) based on magnetoencephalographic (MEG) signals will normalize maladapted cortical representation and relieve pain. Methods This study included 10 phantom limb patients (9 brachial plexus root avulsion and 1 amputee). MEG signals during movements of the phantom hand or intact hand were used to train the decoder inferring movements of each hand. The robotic hand was controlled by the decoder. Patients controlled the robotic hand by moving the phantom hand. The training effects were compared among trainings with the phantom decoder, real hand decoder, and random decoder in a randomized cross-over trial. Results BMI training with the phantom decoder increased the decoding accuracy of phantom hand movements and pain. In contrast, BMI training with the intact hand decoder reduced accuracy and pain. Discussion It was suggested that BMI training to modulate the motor representation of phantom hand controlled pain. The sensorimotor cortical plasticity might induce pain. Conclusions and Significance Phantom limb pain was controlled by BMI training to induce sensorimotor cortical plasticity. [ABSTRACT FROM AUTHOR]