Abstracts

Currently, neural activity and focus localization in epileptic patients is essential for pre-surgical evaluation. Several methods have been devised to locate activity by applying combinations of EEG, MEG, PET, SPECT, and fMRI. Phase-Dynamic Quantification combines Recurrence Quantification Analysis, phase correlation, and three-dimensional temporal and spatial alignment to track seizure activity along with pre- and postictal responses. Utilizing high-frequency (12-25kHz) multi-channel brain activity, we introduce a method for correlating dynamic temporal phase which permits tracking of the seizure focus. Multichannel neuronal potentials were collected synchronously over the course of 2 mos from a chronically seizing animal model of limbic epilepsy (n=1). Arrays of tungsten microwire electrodes were stereotaxically implanted in the dentate and CA1-2 of the hippocampus. Neuronal activity was recorded at 24414.1Hz. Electrode placement and CA1-2/Dentate targeting were verified post-mortem using a high-field (17.6 Tesla) MRI brain imaging instrument. Hippocampus depth and grid recording were also obtained in humans undergoing presurgical epilepsy evaluations (n=2). Cortical activity was recorded continuously at 400Hz. All data sets were analyzed for phase correlation. In all time series analyzed, the results demonstrated a well-defined seizure path within the epileptogenic focus. In each human data set, phase correlation coincided with the seizure focus that was determined by visual analysis of temporal lobe depth and grid recordings.
Figure shows dynamic moving focus phase correlation using three 400 Hz signals. Phase-Dynamic Quantification reveals epilepsy as a highly organized contiguous neural pathway that can be localized and tracked. This method may of clinical utility assist with seizure localization.[figure1] (Supported by Office of Naval Research Funding, National Institutes of Health, National Science Foundation, Children[apos]s Miracle Network.)