BASAL TEMPORAL LANGUAGE AREA (BTLA) AND LATERALITY INDEX MEASURED BY MEG DURING LANGUAGE TASKS
Abstract number :
2.218
Submission category :
Year :
2003
Submission ID :
3931
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Susan M. Bowyer, Toya V. Fleming, Karen M. Mason, John E. Moran, Brien J. Smith, Norman Tepley, Gregory L. Barkley Neurology, Henry Ford Hospital, Detroit, MI; Physics, Oakland University, Rochester Hills, MI; School of Medicine, Wayne State University, D
The determination of cortical areas, critical for language processing, is necessary prior to any surgical resection. The goal of non-invasive imaging techniques such as Magnetoencephalography (MEG) and functional Magnetic Resonance Imaging (fMRI) is to replace the current gold standards of invasive-intracranial mapping and semi-invasive Wada testing for determining language processing areas. Consequently, the significance of the basal temporal language area (BTLA) and determination of the language dominant hemisphere were investigated with MEG.
MEG recordings (148-channel WH Magnes) were made on 6 control subjects and 12 patients, diagnosed with partial epilepsy, during semantic (verb generation) and non-semantic (picture naming) language tasks. Eight of the patients also underwent successful semi-invasive Wada testing that determined their language dominant hemisphere. MEG data were analyzed by MR-FOCUSS, a current density imaging technique. A laterality index (LI) was calculated for each patient from this solution to determine which hemisphere had more neural activation during these language tasks.
A significant MEG signal arising from activation in the BTLA was found in the fusiform gyrus 130-180ms after stimulus onset during Verb Generation. This activation was seen in 5/6 controls and 9/12 patients with localization-related epilepsy. The LI index calculated for 8 of the epilepsy patients was in agreement with their Wada test results.
BTLA can be visualized using MEG. Activation is seen during Verb Generation tasks for control subjects and subjects with epilepsy at ~150ms. BTLA activation is not seen during Picture Naming tasks. We suspect that the lack of activation of BTLA in the picture naming task is due to the fact that BTLA is more likely involved in working memory processing rather than language comprehension. The MEG LI determined from the verb generation task agreed with the results from the Wada Test in all eight patients tested. MR-FOCUSS reliably localized and quantified activity in language specific areas. MEG can be used to determine the dominant hemisphere non-invasively, providing less risk to patients than current invasive language lateralization methods.
[Supported by: The United States NIH/NINDS Grant number R01 NS 30914 and L.E.A.R.N.]