Magnetic source imaging (MSI) provided nonredundant information in 33% of patients. In those who have undergone surgery to date, MSI added useful information that changed treatment in 6 (9%), without increasing complications. MSI has benefited 21% who have gone to surgery.

Objective: MEG dipole localization of epileptic spikes is useful in epilepsy surgery for mapping the extent of abnormal cortex and to focus intracranial electrodes. Visually analyzing large amounts of data produces fatigue and error. Most automated techniques are based on matching of interictal spike templates or predictive filtering of the data and do not explicitly include source localization as part of the analysis. This leads to poor sensitivity versus specificity characteristics. We describe a fully automated method that combines time-series analysis with source localization to detect clusters of focal neuronal current generators within the brain that produce interictal spike activity.Methods: We first use an ICA (Independent Components Analysis) method to decompose the multichannel MEG data and identify those components that exhibit spike-like characteristics. From these detected spikes we then find those whose spatial topographies across the array are consistent with focal neural sources, and determine the foci of equivalent current dipoles and their associated time courses. We then perform a clustering of the localized dipoles based on distance metrics that takes into consideration both their locations and time courses. The final step of refinement consists of retaining only those clusters that are statistically significant. The average locations and time series from significant clusters comprise the final output of our method.Results and Significance: Data were processed from four patients with partial focal epilepsy. In all three subjects for whom surgical resection was performed, clusters were found in the vicinity of the resectioned area.Conclusion: The presented procedure is promising and likely to be useful to the physician as a more sensitive, automated and objective method to help in the localization of the interictal spike zone of intractable partial seizures. The final output can be visually verified by neurologists in terms of both the location and distribution of the dipole clusters and their associated time series. Due to the clinical relevance and demonstrated promise of this method, further investigation of this approach is warranted.

Various studies have indicated an impairment of sensory signal processing in schizophrenic patients. Anatomical and functional imaging studies have indicated morphological and metabolic abnormalities in the thalamus in schizophrenia. Other results give evidence for an additional role of cortical dysfunction in sensory processing in schizophrenia. Advanced analysis of human median nerve somatosensory evoked potentials (SEPs) reveals a brief oscillatory burst of low-amplitude and high-frequency activity ( approximately 600 Hz), the so-called high frequency oscillations (HFOs). The present study explores the behavior of HFOs in a cohort of schizophrenic patients in comparison to a group of controls. HFOs in the group of patients appeared with a delayed latency. In the low-frequency part of the SEPs an increase in amplitude was found. These results are interpreted to reflect a lack of somatosensory inhibition in the somatosensory pathway, either at a thalamic or a cortical level.

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