Biofeedback of Slow
Slow cortical potentials (SCPs) of the electroencephalogram (EEG) reflect cortical excitability. Negative SCPs appear in animals as well as in humans before and during epileptic seizures, which are followed by positive potential shifts after their abatement. This leads to the hypothesis that epilepsy involves a deficit in regulating cortical hyperactivation. Operant learning and behavioral principles have been used to develop a treatment program to control SCPs and to teach patients to cope with seizures. The program is described in this chapter, and predictors of outcome are reported. (As in other chapters, italics on first use of a term indicate that the term is included in the glossary at the chapter's end.)
Epilepsy is one of the most common neurological disorders. For every 1000 persons, there are 5 to 10 active cases. Epilepsy is most likely to occur at two periods: the first 10 years of life, and after the age of 60. The annual incidence of new cases is about 50 per 100,000 (Hauser & Hesdorffer, 1990).
The causes of epilepsy are diverse, but in most cases they are unknown. In young children, genetic factors, congenital defects, and developmental disturbances are the most common causes; in elderly patients, mostly cerebrovascular diseases are found.
Epilepsy can be described as a group of neurological conditions that are characterized by recurrent seizures. These seizures are the result of a disturbed balance between excitation and inhibition of neurons that are located predominantly in the cerebral cortex. Exclusively subcortical seizures, and disturbed corticothalamico and corticostriatal circuits, can be observed as well. Depending upon the specific underlying pathophysiological conditions and clinical signs, partial seizures are distinguished from generalized seizures. Partial seizures consist of initial activation of neurons limited to one area of the cortex, the "focus." Patients may