Abstracts

Rationale: Auditory naming (AN) is an ecologically valid method for assessing word-finding deficits and has been reliably interrupted by electrocortical stimulation (ECS) of the temporal lobe (Hamberger et al., 2001). Moreover, AN has been found to be impaired in left vs. right temporal lobe (TL) epilepsy patients and appears to best discriminate these two groups among a number of common neuropsychological (NP) measures (Doss & Risse, 2006). Magnetic Source Imaging (MSI) is a functional neuroimaging procedure, which is being used to localize language specific regions in the brain (Papanicolaou et al., 2004). This study investigated the relationship between MSI TL language activations and performance on language measures by patients undergoing pre-surgical NP evaluation. The hypothesis is that AN will demonstrate the strongest relationship with left hemisphere MSI TL activations. Methods: The sample consisted of 22 subjects (age 18-65 years) with epilepsy and/or brain tumor who had undergone presurgical evaluation at the Minnesota Epilepsy Group. The sample was 59% male and 86% right handed. Left hemisphere pathology was seen in 82%. For MSI language mapping, an auditory word recognition task was used to activate TL language-specific cortex. The MEG unit consisted of a 148-channel Magnes 2500 WH system (4-D Neuroimaging, San Diego, CA) housed in a magnetically shielded room. Single equivalent current dipole (ECD) model across each whole hemisphere was used in the analysis of language data. However, only activations in the lateral right and left TL were retained for further analysis. A language asymmetry index (AI) was calculated using the formula R-L/R+L. Subjects with AI > 0 and < 0 showed a preponderance of language activity sites in the right and left TL, respectively. NP test results were obtained as part of a standard pre-surgical evaluation. The following tests were correlated with both the MSI total TL language activations and MSI AI using a bivariate SPSS procedure: WAIS-III Vocabulary (VOC), Information (INF), and Similarities (SIM), AN, Boston Naming Test (BNT), and D-KEFS Animals fluency (AF). Total correct raw scores were used for each test. Results: In this sample, 78% showed relative left hemisphere dominance with respect to MSI TL language activations. There were no significant correlations between any test and total TL language activations. The following 1-tailed Pearson correlation coefficients (r) between the AI and NP test results were obtained: VOC = -.14 (ns), INF = -.15 (ns), SIM = .09 (ns), BNT = -.38 (p = .04), AF = .08 (ns), and AN = -.41 (p = .03).Conclusions: As predicted, AN demonstrates the strongest relationship to MSI TL language activations among commonly administered language measures. The observed relationship reveals that higher AN scores are associated with a greater preponderance of language activity sources in the left TL. These preliminary results further support the finding that AN is a valid measure of left TL function and the inclusion of this test in presurgical evaluations.