Cortical Localization in Temporal Lobe Epilepsy

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DESCRIPTION (provided by applicant): It is well established that the temporal lobe plays a critical role in language mediation. Yet, the functional-anatomical organization of language within the temporal lobe region is not well understood. This is a significant concern for temporal lobe epilepsy patients who elect surgical treatment for seizure control, because a substantial portion of temporal cortex is removed with this procedure. To preserve verbal abilities, cortical language mapping is often performed to identify "essential" language cortex and spare these areas from resection. Nonetheless, many patients decline post-operatively despite such mapping, primarily with respect to word finding. Although most surgery programs rely on visual object naming to identify 'essential' language cortex, the addition of auditory naming revealed a distinct region in anterior temporal cortex where stimulation impaired auditory but not visual naming. Preliminary follow-up testing suggests that sparing these auditory naming sites preserves word finding whereas resecting these sites results in decline (without affecting seizure outcome). Interestingly, a number of patients declined on both auditory and visual naming, despite the fact that only "pure auditory" sites were resected, and that all visual naming sites were spared. In the proposed studies, psycholinguistic tasks will be used before and after temporal lobe resection to study the role of anterior temporal cortex in the access of words and their meaning. Similar tasks will be used during mapping to delineate language-related structure-function relations at a level of analysis that is not attainable with other methods. Continued post-operative follow-up will assess the reliability of the preliminary findings, and determine whether deficits persist. Seizure outcome will be monitored as well. Primary goals are: 1) To determine how often, and in which patients, removing auditory naming sites results in word finding decline; 2) To determine the extent to which processes involved in word selection and access to word meaning are anatomically distinct, and where these process are represented neuroanatomically, 3) Determine why resection of cortex that appears to support modality-specific (auditory) naming can result in general word finding decline; 4) Determine whether sparing auditory naming sites from resection affects seizure outcome. Results promise deeper understanding of the neuro-functional organization of language, potentially offering improved treatment and preservation of language skills, not only to epilepsy surgery patients, but also to individuals with other neurologically based language disorders.