Time-frequency analysis using the matching pursuit algorithm applied to seizures originating from the mesial temporal lobe.
Departments of 1Neurology, 2Physiology, and 3Neurosurgery, 4Maryland Epilepsy Center, University of Maryland School of Medicine, Baltimore, MD and 5 Laboratory of Medical Physics, Institute of Experimental Physics, Warsaw University, Warsaw, Poland
Key Words: matching pursuit, time-frequency analysis, mesial temporal seizures, intracranial recordings, complex partial seizures
The ability to analyze patterns of recorded seizure activity is important in the localization and classification of seizures. The fact that ictal evolution is typically a dynamic and nonstationary process with signals composed of multiple frequencies can limit or complicate visual and other methods of analysis. The recently developed matching pursuit algorithm permits continuous time-frequency decomposition of signals from selected recording channels. This method was applied to analyze intracranial recordings of nonlesional complex partial seizures originating from mesial temporal structures in nine patients. The matching pursuit method permits detailed time-frequency analyses of the entire seizures, including periods that are rapidly evolving. Periods of seizure initiation, transitional rhythmic activity, organized rhythmic activity and intermittent bursting activity were identified. During the periods of organized rhythmic activity, all seizures of mesial temporal origin analysed had a maximum predominant frequency of 5.3-8.4 Hz with a monotonic decline in frequency over a period of less than 60 seconds. The matching pursuit method is a valuable tool for continuous analyses of entire seizures. These analyses may reveal patterns of activity that may aid in the identification and localization of seizure subtypes.
(Supported by NIH grant NS 33732-01)
Electroenceph. clin. Neurophys. 106:513-521 (1998)