Synchronization Clusters of Interictal Activity in the Lateral Temporal Cortex of Epileptic Patients: Intraoperative Electrocorticographic Analysis

GUILLERMO J. ORTEGA, ‡LISET MENENDEZ DE LA PRIDA, ∗RAFAEL G. SOLA, AND †JESUS PASTOR

EPILEPSIA

WILEY-BLACKWELL PUBLISHING, INC

Año: 2008 vol. 49 p. 269 - 280

0013-9580

Objective: Drug-resistant temporal lobe epilepsy(TLE) can be treated by tailored surgery guided byelectrocorticography (ECoG). Although its value isstill controversial, ECoG activity can provide continuousinformation on intracortical interactionsthat may be useful to understand the pathophysiologyof TLE. The goal of this study is to characterizelocal interactions inmultichannel ECoG recordingsof the lateral cortex of TLE patients using threesynchronization measures and to link this informationwith surgical outcome.Methods: Intraoperative ECoG recordings from 29TLE patients were obtained using grids of 20 electrodes(4 × 5) covering regions T1, T2, and T3 ofthe lateral temporal lobe. Linear correlation, mutualinformation, and phase synchronization werecalculated to quantify lateral intracortical interactions.Surrogate data files were generated to testresults statistically.Results: By distributing locally the interactions betweenthe electrodes, we characterized the spatialpatterns of ECoG activity. We found clustersof synchronized activity at specific areas of thelateral temporal cortex in most patients. Methodologically,linear correlation and phase synchronizationperformed better than mutual informationfor cluster discrimination. ROC analysissuggested that surgical removal of sharply definedsynchronization clusters correlated with seizurecontrol.Conclusions: Our results show that synchronous intraoperativeECoG activity emerges from specificcortical areas that are highly differentiated fromthe rest of the temporal cortex. This suggests thatsynchronization analysis could be used to functionallymap into the temporal cortex of TLE patients.Moreover, our results suggest that these sites mightbe involved in the circuits that participate in clinicalseizures.