Date Approved

8-2018

Graduate Degree Type

Thesis

Degree Name

Engineering (M.S.E.)

Degree Program

School of Engineering

First Advisor

Samhita Rhodes

Second Advisor

Robert Bossemeyer

Third Advisor

Paul Fishback

Academic Year

2017/2018

Abstract

Epilepsy is a common neurological disorder that causes recurrent, unprovoked seizures. Focal, refractory epilepsy is characterized by seizures that start in a specific area in the brain and do not respond to antiepileptic medication. This study was conducted to characterize the connectivity of the focal brain region where seizures originate, known as the epileptogenic zone. Connectivity was measured from electrocorticogram (ECoG) recordings, during seizure events, using information theoretic measures mutual information (MI) and (TE). MI is the amount of information shared between two discrete random variables. TE is the directed information transfer between two discrete random variables. MI provides information about the strength of the connection and TE indicates the direction of information transfer. The analysis is performed in high frequencies, >30 Hz, in order to examine this spectral range of EEG activity, including events called high frequency oscillations (HFOs). The results show three trends in the connectivity of the epileptogenic zone. The first is that there is a reduction in the connectivity of the zone with the rest of the brain just after seizure onset. The second shows the connectivity increases just prior to the termination of the seizure. Finally, the third trend indicates that the direction of the information transfer during the seizure is from outside of the epileptogenic zone to inside. The epileptogenic zone is characterized by a disconnection at seizure onset, fol-lowed by a reconnection just prior to the seizure termination. The results show that the epileptogenic zone exhibits unique properties with respect to connectivity when compared to electrode sites from outside of the zone. These unique behaviors can help in accurately identifying the epileptogenic zone, thus leading to its successful removal.

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