Martin A. Koch

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To achieve a deeper understanding of the brain, scientists, and clinicians use electroencephalography (EEG) and magnetoencephalography (MEG) inverse methods to reconstruct sources in the cortical sheet of the human brain. The influence of structural and electrical anisotropy in both the skull and the white matter on the EEG and MEG source reconstruction is(More)
Language ability and handedness are likely to be associated with asymmetry of the cerebral cortex (grey matter) and connectivity (white matter). Grey matter asymmetry, most likely linked to language has been identified with voxel-based morphometry (VBM) using T(1)-weighted images. Differences in white matter obtained with this technique are less consistent,(More)
This article examines functional and anatomical connectivity in healthy human subjects measured with magnetic resonance imaging methods. Anatomical connectivity in white matter is obtained from measurements of the diffusion tensor. A Monte-Carlo simulation determines the probability that a particle diffuses between two points, with the probability of a jump(More)
BACKGROUND The neuronal basis of persistent developmental stuttering is unknown. The disorder could be related to a reduced left hemisphere dominance, which functional neuroimaging data suggest might lead to right hemispheric motor and premotor overactivation. Alternatively, the core deficit underlying stuttering might be located in the speech-dominant left(More)
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative system disorder affecting both upper and lower motor neurons. Despite supportive electrophysiological investigations, the involvement of the upper motor neuron is often difficult to assess at an early stage of disease. Diffusion tensor MRI provides an estimate of the orientation of fibre(More)
In the monkey the lateral bank of the anterior part of the intraparietal sulcus (area AIP), contains neurons that are involved in visually guided, object-related hand movements. It has also been shown that neurons in the caudal part of the intraparietal sulcus (area CIP) preferentially respond to 3D surface orientation. According to these results, it has(More)
We used diffusion tensor imaging (DTI) to assess Wallerian degeneration of the pyramidal tract within the first 2 weeks after ischemic stroke, and correlated the extent of Wallerian degeneration with the motor deficit. Nine patients with middle cerebral artery stroke were examined 2-16 days after stroke by DTI and T2-weighted MRI. We measured fractional(More)
Stejskal and Tanner's ingenious pulsed field gradient design from 1965 has made diffusion NMR and MRI the mainstay of most studies seeking to resolve microstructural information in porous systems in general and biological systems in particular. Methods extending beyond Stejskal and Tanner's design, such as double diffusion encoding (DDE) NMR and MRI, may(More)
Double wave vector diffusion weighting uses gradients along two different directions between excitation and acquisition. It has been shown theoretically that for restricted diffusion the signal amplitude in such an experiment can depend on the angle between the two gradient vectors. The highest amplitude is obtained with antiparallel orientation, and the(More)
Transcranial magnetic stimulation (TMS) can be used to probe distinct aspects of excitability of the primary motor hand area (M1(Hand)). The motor threshold (MT) reflects the trans-synaptic excitability of corticospinal output neurons. The MT corresponds to the minimal intensity at which TMS evokes a contralateral motor response. Here, we employed(More)