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Neurodynamic imaging - insight into neurocognitive development and disorders

Introduction Magnetoencephalography (MEG) represents non-invasive and non-contact measurements of tiny extracranial magnetic fields (on the order of 100 fT) evoked by sensory and cognitive processes. Its millisecond temporal resolution allows for a direct and real-time monitoring of neuronal activity. The application of source modeling, statistical tools, and cortical oscillation analysis provides a unique insight into spatio-temporal tracking of cortical pathways not matched by other techniques. Neural oscillatory synchronization has been proposed as a dynamic link between the different brain areas engaged into the same perceptual or cognitive process. The extraordinary sensitivity of the measured magnetic signals to the primary neuronal current of interest demonstrated great functional anatomical diversity across subjects and emphasized the need for a within subject as opposed to an across subject analysis. It is to be expected that the individual processing strategies are reflected even more clearly in the timing than in the sites of cortical activation. MEG studies can contribute to the understanding of cerebral activation sequences in healthy subjects and in patients with neurological or psychiatric diseases, as well as in person with special cognitive abilities. Materials & Methods SQUID coupled neuromagnetometers, hundreds of which are distributed over the entire head in the modern whole-head systems, are typically housed in magnetically shielded rooms. Recent sensor developments in Japan and at the Los Alamos National Laboratory indicate that special design of helmets could allow for a good quality of neuromagnetic measurements even outside the shielded rooms. A range of commercial and research software packages are available for display and spatio-temporal characterization and analysis of MEG data. Results Millisecond temporal resolution of MEG and spatio-temporal source localization procedures have proven successful in the localization of, for example, multiple cortical representations of the visual field onto the human cortex, their retinotopic and functional organization as well as the first demonstration of the effects of spatial visual attention in the primary visual cortex via feedback mechanisms which occur later in time, around 150 ms post-stimulus. Neurodynamic imaging is increasingly contributing to our understanding of the neurocognitive development and maturation by identifying the neural mechanisms of normal cognitive processes which could lead to an understanding how they are injured/perturbed in mental illnesses. While all modern functional brain imaging methods have been used in a range of clinical studies, MEG has already entered into routine clinical protocols for the localization of epileptic foci and pre-surgical functional mapping. Conclusions A few MEG studies reviewed here demonstrate the capabilities of neurodynamics imaging since these techniques could be used repetitively and over prolonged periods of time with no harm or discomfort to children and adults alike to examine human neurocognitive development in health and disease.

neurodynamic imaging; neurocognitive development; functional brain organization

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