02512nas a2200289   4500008004100000022001400041245008600055210006900141300001200210490000800222520158400230653001701814653003901831653002701870653002501897100002701922700001901949700002401968700002101992700002102013700002402034700002502058700002302083700002602106700001902132856007102151       2019                        eng d  a0165-027000aA quantitative method for evaluating cortical responses to electrical stimulation0 aquantitative method for evaluating cortical responses to electri  a67 - 750 v3113 aBackground Electrical stimulation of the cortex using subdurally implanted electrodes can causally reveal structural connectivity by eliciting cortico-cortical evoked potentials (CCEPs). While many studies have demonstrated the potential value of CCEPs, the methods to evaluate them were often relatively subjective, did not consider potential artifacts, and did not lend themselves to systematic scientific investigations. New method We developed an automated and quantitative method called SIGNI (Stimulation-Induced Gamma-based Network Identification) to evaluate cortical population-level responses to electrical stimulation that minimizes the impact of electrical artifacts. We applied SIGNI to electrocorticographic (ECoG) data from eight human subjects who were implanted with a total of 978 subdural electrodes. Across the eight subjects, we delivered 92 trains of approximately 200 discrete electrical stimuli each (amplitude 4–15 mA) to a total of 64 electrode pairs. Results We verified SIGNI's efficacy by demonstrating a relationship between the magnitude of evoked cortical activity and stimulation amplitude, as well as between the latency of evoked cortical activity and the distance from the stimulated locations. Conclusions SIGNI reveals the timing and amplitude of cortical responses to electrical stimulation as well as the structural connectivity supporting these responses. With these properties, it enables exploration of new and important questions about the neurophysiology of cortical communication and may also be useful for pre-surgical planning.10aConnectivity10aCortico-cortical evoked potentials10aElectrical stimulation10aElectrocorticography1 aCrowther, Lawrence, J.1 aBrunner, Peter1 aKapeller, Christoph1 aGuger, Christoph1 aKamada, Kyousuke1 aBunch, Marjorie, E.1 aFrawley, Bridget, K.1 aLynch, Timothy, M.1 aRitaccio, Anthony, L.1 aSchalk, Gerwin  uhttp://www.sciencedirect.com/science/article/pii/S016502701830279602102nas a2200229   4500008004100000245013500041210007100176260001200247490000700259520133100266653002101597653001601618653001701634653002701651653003501678653002501713653002501738100001701763700002101780700002301801856004801824       2011                        eng d00aSpace–time network connectivity and cortical activations preceding spike wave discharges in human absence epilepsy: a MEG study.0 aSpace–time network connectivity and cortical activations precedi  c05/20110 v493 aTo describe the spatial and temporal profiles of connectivity networks and sources preceding generalized spike-and-wave discharges (SWDs) in human absence epilepsy. Nonlinear associations of MEG signals and cluster indices obtained within the framework of graph theory were determined, while source localization in the frequency domain was performed in the low frequency bands with dynamic imaging of coherent sources. The results were projected on a three-dimensional surface rendering of the brain using a semi-realistic head model and MRI images obtained for each of the five patients studied. An increase in clustering and a decrease in path length preceding SWD onset and a rhythmic pattern of increasing and decreasing connectivity were seen during SWDs. Beamforming showed a consistent appearance of a low frequency frontal cortical source prior to the first generalized spikes. This source was preceded by a low frequency occipital source. The changes in the connectivity networks with the onset of SWDs suggest a pathologically predisposed state towards synchronous seizure networks with increasing connectivity from interictal to preictal and ictal state, while the occipital and frontal low frequency early preictal sources demonstrate that SWDs are not suddenly arising but gradually build up in a dynamic network.10aAbsence epilepsy10aBeamforming10aConnectivity10aMagnetoencephalography10aNonlinear association analysis10aSmall world networks10aSpike wave discharge1 aGupta, Disha1 aOssenblok, Pauly1 aLuijtelaar, Gilles  uhttp://www.ncbi.nlm.nih.gov/pubmed/21533620