NEUROPSYCHOLOGICAL AND COGNITIVE STUDIES IN EPILEPSY

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We have been performing imaging studies of language organization in normal controls and patients with epilepsy. Using positron emission tomography (PET), activation of cerebral blood flow (CBF) associated with word and object recognition, auditory comprehension, and phoneme, word, and sentence production are localized in the brain. Data from subdural stimulation, PET, and magnetic resonance imaging (MRI) are integrated using digital image processing techniques. The combined stimulation and PET data allow us to study the relationship between activation and disruption of cognitive activity, and to form more accurate concepts of the organization of cerebral function. These studies will elucidate the function of regions such as the basal temporal language area, which are of clinical importance when surgery for uncontrolled seizures is planned. Digital signal processing tech~niques are used to confirm anatomic localization of functional mapping. Using surface fitting algor~ithms, PET, CT, MRI, and subdural electrode positons are aligned. In PET experiments, rest conditions are averaged and subtracted from activated conditions, in order to reveal reigons of inreased blood flow during task performance. We found a high concordance between PET~CBF and subdural stimulation mapping using a number of different functional tets. This result shows the practicality of noninvasive preoperative functional brain mapping, and also demonstrates the close correlation of disruption and activation studies.