Abstracts

Rationale: Using task-based language fMRI to evaluate language function pre-surgically improves post-surgical language outcomes in drug-resistant epilepsy patients. Our recent study demonstrated that a language fMRI task also activates the medial temporal lobes (MTL), a hub for memory function, on an individual basis in adults and children with and without epilepsy (Sepeta et al., 2016). Language fMRI thus may also help predict memory outcomes, and establishing the relationship between MTL activation and cognition has implications for predicting memory outcomes after epilepsy surgery. We explored the functional significance of MTL activation during language fMRI and hypothesized that greater MTL activation and laterality would be associated with better performance on neuropsychological measures of language and memory. Methods: Sixty-five controls and patients with left-hemisphere focal epilepsy (patients, n = 17, mean age = 9.9 ± 2.0; controls, n = 48; mean age = 9.1 ± 2.6) completed a language task (auditory description decision task) in 3T fMRI. Images were processed in SPM8 using a bilateral MTL ROI. Total MTL activation as well as Laterality Index (LI) were calculated after processing. Participants also completed neuropsychological assessment for language (CELF-IV), and verbal (CVLT-C) and visual (CMS Dot Locations) memory. We used linear regression in SPSS to test whether total MTL voxel count and/or laterality predicted neuropsychological performance. Results: Neither amount of activation nor mean MTL LI differed between controls and patients (p 0.24); both groups displayed bilateral mean LI. For participants overall, total amount of MTL activation significantly predicted 12% of the variance in expressive language on the CELF (CELF expressive: p=0.008), such that greater total MTL activation was associated with better language. Neither MTL activation nor LI predicted memory for participants overall. However, MTL LI predicted 31% of the variance in CVLT-C short-delay free recall (p=0.02) for patients only. Conclusions: These findings suggest that total MTL activation across both hemispheres benefits expressive language, and that the MTL may support language function. Furthermore, our previous work has shown that MTL activation is left-lateralized in adults during the same language fMRI task as used in the current study, and this lateralization is correlated with better verbal memory performance. While mean MTL activation in this pediatric sample is bilateral in both controls and patients, individual patterns are variable, and greater left lateralization was associated with better performance on a verbal memory measure. These findings suggest that the relationship between MTL activation and verbal memory may evolve over development, which has implications for timing of epilepsy surgery in pediatric patients. Therefore, future analyses will include more participants, including adults, to examine developmental differences and effects of surgery. Funding: This work was supported by: Avery Translational Research Career Development Program Award [through the Clinical and Translational Science Institute at Children’s National (CTSI-CN) to L.N.S.]Susan S. Spencer Clinical Research Training Fellowship [to L.N.S.]K23 NS093152 from NINDS to LNS