Magnetic Resonance Imaging (MRI)

We studied 12 patients with brain tumors in the vicinity of the sensorimotor region to provide a preoperative three-dimensional visualization of the functional anatomy of the rolandic cortex. We also evaluated the role of cortex-muscle coherence analysis and anatomical landmarks in identifying the sensorimotor cortex. The functional landmarks were based on neuromagnetic recordings with a whole-scalp magnetometer, coregistred with magnetic resonance images.

To determine if interaural time differences (ITDs) in binaural stimuli affect the middle-latency auditory evoked fields (AEFs) in the same manner as they affect the N100m deflection, neuromagnetic responses were recorded over the whole head using a 122-channel SQUID magnetometer. Binaural stimuli were lateralized to three positions, left, midline, and right, on the basis of ITDs. The N100m was significantly larger to stimuli with contralaterally-leading ITDs than to stimuli with no, or with ipsilaterally-leading ITDs.

Visual perceptual learning (VPL) is consolidated during sleep. However, the underlying neuronal mechanisms of consolidation are not yet fully understood. It has been suggested that the spontaneous brain oscillations that characterize sleep stages are indicative of the consolidation of learning and memory. We investigated whether sleep spindles and/or slow-waves are associated with consolidation of VPL during non-rapid eye movement (NREM) sleep during the first sleep cycle, using magnetoencephalography (MEG), magnetic resonance imaging (MRI), and polysomnography (PSG).

Previously, we introduced the use of individual cortical location and orientation constraints in the spatiotemporal Bayesian dipole analysis setting proposed by Jun et al. ([2005]; Neuroimage 28:84-98). However, the model's performance was limited by slow convergence and multimodality of the numerically estimated posterior distribution. In this paper, we present an intuitive way to exploit functional magnetic resonance imaging (fMRI) data in the Markov chain Monte Carlo sampling -based inverse estimation of magnetoencephalographic (MEG) data.

The Landau-Kleffner syndrome (LKS) is characterized by electroencephalographic spike discharges and verbal auditory agnosia in previously healthy children. We recorded magnetoencephalographic (MEG) spikes in a patient with LKS, and compared their sources with anatomical information from magnetic resonance imaging. All spikes originated close to the left auditory cortex. The evoked responses were contaminated by spikes in the left auditory area and suppressed in the right--the latter responses recovered when the spikes disappeared.

The cerebellum is heavily involved in the control of accurate eye movements. Cerebellar lesions typically results in nystagmus and dysmetria, inability to stop the eyes at the end of a conjugate movement. Up to now, no cerebellar activity has been identified from non-invasive electrophysiological data. Here we report on neuromagnetic signals of eight healthy subjects in association with visually guided horizontal saccades.

BACKGROUND: TMS activations of white matter depend not only on the distance from the coil, but also on the orientation of the axons relative to the TMS-induced electric field, and especially on axonal bends that create strong local field gradient maxima. Therefore, tractography contains potentially useful information for TMS targeting.

Blood oxygen level dependent-functional magnetic resonance imaging (BOLD-fMRI) and magnetoencephalographic (MEG) signals are both coupled to postsynaptic potentials, although their relationship is incompletely understood. Here, the wide range of BOLD-fMRI and MEG responses produced by auditory cortex was exploited to better understand the BOLD-fMRI/MEG relationship. Measurements of BOLD and MEG responses were made in the same subjects using the same stimuli for both modalities. The stimuli, 24-s sequences of click trains, had duty cycles of 2.5, 25, 72, and 100%.

We recorded somatosensory evoked fields (SEFs) from 10 healthy subjects to ulnar and median nerve stimuli presented at random intervals of 2.4-21.6 s. The subjects either counted the stimuli or ignored them by reading a book. The stimuli activated in both conditions the contralateral SI cortex, the ipsi- and contralateral SII cortices, and the posterior parietal cortex (PPC), in line with earlier observations. In addition, a novel response was observed in nine subjects at 120-160 ms.