A simple wavelet-based test for evoked responses.

Statistically valid detection of evoked responses from magnetoencephalographic (MEG) sensors is complicated by temporal autocorrelation. By decorrelating time series and transforming them toward normality, the discrete wavelet transform (DWT) allows the analyst to test for an association between stimulus and sensor time series with appropriate degrees of freedom. Eswaran et al.

Prediction of labor in term and preterm pregnancies using non-invasive magnetomyographic recordings of uterine contractions.

Objective: The purpose of this study was to characterize the noninvasive magnetic field recordings of the uterine electrophysiological activity in patients reporting onset of uterine contractions.

Study Design: Transabdominal magnetomyographic (MMG) recordings were performed with the use of the SARA system's 151 primary magnetic sensors (CTF Systems Inc, Coquitlam, British Columbia, Canada). Eleven term and 4 preterm patients participated in the study.

Fetal MEG redistribution by projection operators.

The fetal magnetoencephalogram (fMEG) is measured in the presence of large interference from the maternal and fetal magnetocardiograms. This interference can be efficiently attenuated by orthogonal projection of the corresponding spatial vectors. However, the projection operators redistribute the fMEG signal among sensors.

Human fetal brain imaging by magnetoencephalography: verification of fetal brain signals by comparison with fetal brain models.

Fetal magnetoencephalogram (fMEG) is measured in the presence of a large interference from maternal and fetal magnetocardiograms (mMCG and fMCG). This cardiac interference can be successfully removed by orthogonal projection of the corresponding spatial vectors. However, orthogonal projection redistributes the fMEG signal among channels.

A placebo-controlled randomized crossover trial of the N-methyl-D-aspartic acid receptor antagonist, memantine, in patients with chronic phantom limb pain.

Unlabelled: In the present study we investigated the effect of the N-methyl-D-aspartic acid (NMDA) receptor antagonist memantine (30 mg/d) on the intensity of chronic phantom limb pain (PLP) and cortical reorganization. In 8 patients with chronic PLP, memantine was tested in a placebo-controlled double-blinded crossover trial of 4 wk duration per trial. The intensity of PLP was rated hourly by the patients on a visual analog scale during baseline and both treatment periods.

Analysis of uterine contractions: a dynamical approach.

The development of suitable techniques for quantifying mechanical and electrophysiological aspects of uterine contractions has been an active area of research. The uterus is a physiological system consisting of a large number of interacting muscle cells. The activity of these cells evolves with time, a trait characteristic of a dynamical system.

[New perspectives in intrauterine surveillance with the fetal magnetoencephalogram].

Purpose: Despite intensive research and surveillance up to now one has failed to reduce cerebral handicaps in newborn. Fetal heart rate tracing (CTG) and Doppler have reduced the number of subpartal severe asphyxia and fetal death. But, 90% of cerebral damage is a result of antepartal problems.

First magnetomyographic recordings of uterine activity with spatial-temporal information using 151 channel sensor array (SARA).

The lack of an effective method for the diagnosis and management of labor points to the need for a new device. SARA-SQUID Array for Reproductive Assessment, is capable of recording spatial-temporal biomagnetic activity. The SARA system is first of its kind in the world dedicated to maternal-fetal research.

Noninvasive antepartum recording of fetal S-T segment with a newly developed 151-channel magnetic sensor system.

Objective: The objective of this study was to evaluate the efficiency of the detection of the S-T segment in the fetal PQRST complex that is recorded in the antepartum period with the use of a newly developed noninvasive 151-channel magnetic sensor array.

Study Design: One hundred two fetal magnetocardiographic recordings were performed on normal fetuses with gestational ages that ranged from 27.5 to 39.

Effects of hydration and hyperventilation on cortical complexity.

The effects of hydration and hyperventilation on cortical complexity were investigated in a sample of 19 healthy volunteers in a double-blind placebo design using magnetoencephalographic recordings. The subjects were asked to abstain from the intake of liquids 18 h before the study. Spontaneous magnetoencephalograms (MEG) were recorded before and after drinking 750 ml water (WAT group: nine subjects) or saline solution (SAL group: ten subjects) with eyes closed and open and during hyperventilation (HV) with eyes open.

Combining MEG and MRI with neuronavigation for treatment of an epileptiform spike focus in the precentral region: a technical case report.

Background: Epileptic foci are often located in the vicinity but not necessarily within the boundaries of intra-axial brain tumors. Resection of these tumors is based on two major goals: first, maximizing tumor removal without provoking new neurologic deficits, and second, minimizing epileptic seizure activity. Magnetic source imaging (MSI) depicts the generators of magnetic fields overlaid on individual magnetic resonance (MR) images.

Complexity of visual stimuli and non-linear EEG dynamics in humans.

The effects of stimulus complexity on the nonlinear electrical brain (EEG) dynamics were investigated in a sample of 24 healthy volunteers. Stimuli used were either a single mechanical low-friction pendulum with a periodic movement (temporal frequency about 1 Hz) or a double-pendulum with a chaotic movement, which were observed for 2-3 min in each case. The prediction that a more complex visual stimulus (double-pendulum) increases the dimensional complexity of brain activity as compared to a simple visual stimulus (single-pendulum), was confirmed by determination of pointwise correlation dimension.

Application of wavelet transform to uterine electromyographic signals recorded using abdominal surface electrodes.

Objective: The aim of this study was to explore the use of the wavelet transform technique to extract and display simultaneously the time, frequency and amplitude information corresponding to electromyographic (EMG) activity of the uterus during labor recorded using abdominal electrodes.

Methods: Uterine EMG signals were recorded from patients in labor using three pairs of electrodes placed across the maternal abdomen. In all the patients uterine activity was also recorded either from an intrauterine pressure catheter (IUPC) or a tocodynamometer.

Short-term serial magnetoencephalography recordings offetal auditory evoked responses.

The study objective was to determine whether short-term serial magnetoencephalographic (MEG) measurements would increase the odds in favor of obtaining fetal auditory evoked responses in normal fetuses. The recordings were performed in two phases using the newly developed 151-channel fetal MEG system, superconducting quantum interference device array for reproductive assessment. Ten pregnant subjects with gestational ages ranging from 30-35 weeks were recruited to participate.

Magnetoencephalographic recordings of visual evoked brain activity in the human fetus.

We investigated the feasibility of recording visual evoked brain activity in the human fetus by use of non-invasive magnetoencephalography (MEG). Each recording lasted 6 min and consisted of a sequence of 180 flashes with 33 ms duration delivered 2 s apart over the maternal abdomen. Four of ten fetuses included showed a response; the ranges of amplitude and latency of peak response were 15-30 x 10(-15) Tesla and 180-390 ms, respectively.

First magnetomyographic recordings of uterine activity with spatial-temporal information with a 151-channel sensor array.

Objective: The purpose of this study was to examine the feasibility of recording the spatial-temporal magnetomyographic activity from the pregnant uterus with the use of the newly developed 151-channel noninvasive device, known as the superconducting quantum interference device array for reproductive assessment.

Study Design: Uterine magnetomyographic signals were recorded from 10 pregnant subjects with the 151-channel sensor array curved to fit the pregnant abdomen. The recording sessions were 16 minutes in length, with a sampling rate of 250 Hz.

Effects of water on cortical excitability in humans.

The effects of water on cortical excitability, measured using magnetoencephalographic recordings, were investigated in a sample of 19 healthy volunteers in a double-blind, placebo experiment comparing water with saline solution. Spontaneous magnetoencephalogram as well as auditory-evoked magnetic fields were recorded before and after the drinking of 750 mL water (9 subjects) or saline solution (10 subjects) and during and after hyperventilation following the drinking conditions. Hyperventilation was used to enhance the hypothesized synchronizing effect of water on spontaneous magnetoencephalographic activity.

Early activation of the primary somatosensory cortex without conscious awareness of somatosensory stimuli in tumor patients.

The primary sensory cortex has usually been regarded as a necessary step in the information processing stream leading to conscious awareness. Recently, it has been proposed that that higher order associative areas rather than the primary sensory areas are the neural basis of conscious perception. In two patients with tumors near the central region we recorded magnetic somatosensory evoked fields.

Multiple frequency steady-state evoked magnetic field mapping of digit representation in primary somatosensory cortex.

Magnetic source imaging of multiple frequency steady-state somatosensory evoked responses was examined using a 151-channel magnetoencephalography (MEG) system and a dual-channel electrical stimulator. Somatotopy of digit representation was studied in healthy subjects and effects of injury-related cortical plasticity in patients with unilateral transections of the median or the ulnar nerve. Dipole source locations exhibited somatotopic order with overlap between neighboring digits.

[Neural networks and pain processing. New insights from imaging techniques].

Imaging techniques with high spatial and temporal resolution (PET,fMRI, MEG) provide detailed information about the brains' processing of pain. Structures detected by these techniques are not understood as pain centers but as nodal points of a dynamic network which is influenced by physiological and psychological input. Imaging techniques can be used for the investigation of different pain components.

Cortical reorganization after digit-to-hand replantation.

Functional recovery after digit-to-hand replantation depends on the interaction of various factors. In addition to peripheral mechanisms, cortical and subcortical reorganization of digit representation may play a substantial role in the recovery process. However, cortical processes during the first months after replantation are not well understood.

Neuroimaging of chronic pain: phantom limb and musculoskeletal pain.

New developments in brain imaging lead to a better understanding of cortical and subcortical processes involved in pain perception and the establishment of chronic pain. For different forms of chronic pain long-term changes in cortical structures have been described. In patients with phantom limb pain and back pain alterations in the somatotopic organization of the primary somatosensory (SI) could be observed.

Activity patterns of human somatosensory cortex adapt dynamically to stimulus properties.

Long-term synchronous tactile stimulation of two sites of the body results in integrated, overlapping cortical representations whereas asynchronous stimulation leads to segregated representations. To investigate the cortical capacity to adapt dynamically to stimulation properties 22 subjects were stimulated at digits 1, 3 and 5 of both hands in either random or fixed order. Changes in the functional organization of the somatosensory cortex were inferred by neuromagnetic source analysis based on somatosensory evoked magnetic fields.