Brain Topography, Volume 11, Number 1,1998 13 Application of the Directed Transfer Function Method to Mesial and Lateral Onset Temporal Lobe Seizures Piotr J. Franaszczuk*^ and Gregory K. Bergey *^+ Summary: The directed transfer function (DTF) method is a multichannel analysis based on an autoregressive model that detects flow of seizure activity. This report extends the application of the DTF method to compare patterns of flow of seizures with different sites of origin. Analysis of a seizure originating from mesial temporal structures is compared with a seizure originating from lateral temporal neocortex; both complex partial seizures were recorded with intracranial electrodes that combine subdural grid arrays and depth electrodes. The DTF method has the potential to determine patterns of flow of activity, including periods when visual analysis of the intracranial ictal EEG may not allow for definitive source localization. The extension of the DTF analyses into integrated DTF (IDTF) formats is also illustrated. When activity of a relatively discrete frequency can be identified, the IDTF analysis facilitates display of patterns of flow of this selected activity. Introduction Accurate localization of seizure onset is of para- mount importance in the analysis of seizures in patients being considered for surgery for intractable epilepsy. While many seizures can be localized from ictal scalp EEG, other seizures require intracranial ictal recordings (ICEEG) for accurate localization and still other seizures (e.g., neocortical onset seizures) may be difficult to local- ize even with extensive intracranial recording arrays (Burgerman et al. 1995; Matsuoka and Spencer 1993; Wal- czak 1995; Williamson 1992). The recently described di- rected transfer function (DTF) method (Kaminski and Blinowska 1991; Franaszczuk et al. 1994) offers the prom- ise of detecting patterns of flow of seizure activity, poten- tially allowing source localization after regional seizure * Maryland Epilepsy Center, Baltimore, MD, USA. ^ Department of Neurology, Baltimore, MD, USA. + Department of Physiology, University of Maryland School of Medicine and Medical Center, Baltimore, MD, USA. Accepted for publication: April 21,1998. We would like to thank C.P. Fleming, R.EEG.T. for her assistance in obtaining and processing the EEG recordings. Our colleagues at the Maryland Epilepsy Center, Drs. S. Alemayehu, E. Barry, H. Eisenberg, A. Krumholz, F. Mwaisela and A. Wolf participated in the care of these patients. This study was supported by NIH grant NS 33732-01. Correspondence and reprint requests should be addressed to Piotr J. Franaszczuk, Ph.D., Maryland Epilepsy Center, Department of Neu- rology, University of Maryland School of Medicine and Medical Center, 22 South Greene Street, Baltimore, MD, 21201 USA. Fax: 410-706-0186 email: pfranasz@umaryland.edu Copyright © 1998 Human Sciences Press, Inc. spread when visual EEG analysis, even of intracranial recordings, may be relatively unrevealing. The DTF method is a multichannel analysis based on an autore- gressive model that can be appropriately applied to the analysis of ictal and interictal EEGdata providing certain criteria are met. Other investigators have recently ap- plied these methods to analyses of flow of activity in rat hippocampus and adjacent structures (Korzeniewska et al. 1997) and to propagation of EEG activity during sleep in humans (Kaminski et al. 1997). In a previous report (Franaszczuk et al. 1994) the DTF method was applied for the first time to multichan- nel intracranial ictal recordings from patients with known mesial temporal lobe onset seizures to describe the appropriate application of these analyses for seizure activity. It was demonstrated that, if quasi-stationary epochs of the ictal recordings were selected, the DTF method provided reliable detection of patterns of sei- zure flow, both at times early in the evolution of the seizure when visual analysis of the ICEEG revealed a clear focus of seizure activity, and later, following re- gional propagation of seizure activity in temporal lobe, when visual analysis of the ICEEG did not clearly reveal a focal discharge. We now extend these investigations to applications of the DTF method to temporal lobe complex partial seizures originating from lateral tempo- ral neocortex and compare these analyses with patterns of propagation of complex partial seizures of mesial temporal lobe origin. In addition, we describe the method of selecting a specific frequency band of interest and generating an integrated directed transfer function Key words: Directed transfer function; Temporal lobe; Complex partial seizure; Propagation; Autoregressive model.