The Baboon Model of Epilepsy: Current Applications in Biomedical Research

Abstract

Epilepsy is a condition of recurrent, unprovoked seizures (Adams and Victor, 1993). Seizures are episodic changes in behavior associated with a synchronized electrical discharge from the populations of neurons in the cerebral cortex. To classify human epilepsies as focal or generalized, clinicians rely on a seizure description combined with electroencephalography (EEG) (Commission on the Classification and Terminology of the International League Against Epilepsy, 1981 and 1989). Because seizures are rarely recorded in brief EEG samples, clinicians rely on the the detection of interictal (between seizures) epileptic discharges, which serve as markers for the seizure type. Focal epilepsies begin with focal symptomatology and are associated with interictal epileptic discharges (IEDs) that are focal or lateralized to one cerebral hemisphere. Generalized epilepsies are associated with sudden unresponsiveness or bilateral motor symptoms at onset, and IEDs tend to involve both hemispheres simultaneously. While most focal epilepsies are symptomatic, related to a localized structural lesion, generalized epilepsies are predominantly idiopathic, and considered to be heritable. Some epilepsies, mainly idiopathic in characterization, include seizure types that are elicited by specific stimuli. Photosensitivity describes an enhanced cerebral excitation by exposure to intermittent light stimulation (ILS), such as a flickering light source. Photosensitivity is rare, occurring in about 5% of people with epilepsy, but is more frequently encountered in idiopathic or symptomatic generalized epilepsies (Janz and Durner, 1997). Most photosensitive patients have juvenile myoclonic epilepsy (JME), with a prevalence of 30–60% (Janz and Durner, 1997). EEG findings of photosensitivity include the activation of IEDs, or photoparoxysmal responses, and the activation of myoclonic or generalized tonicclonic seizures, or photoconvulsive responses. Because all of these responses are associated with cortical excitability and a predisposition to seizures, they may be referred to as photoepileptic responses. Because of the prevalence of