Abstracts

Rationale: Chronic temporal lobe epilepsy (TLE) in both children and adults is now known to be associated with widespread neuropsychological abnormalities, including executive function (EF). The timing and course of these diffuse cognitive abnormalities remains to be clarified as well as the structural and functional correlates of abnormal EF. Here we examine EF in children with new onset TLE and its substrate using functional neuroimaging. Methods: Fifteen children (ages 8-13) with newly-diagnosed TLE and 15 healthy controls underwent functional neuroimaging while performing the N-Back task. In this task, participants were presented with a series of single consonant letters and instructed to press a button with their dominant hand when the presented letter was the same as the one presented n letters ago. Subjects were tested using three load conditions: 0-back ('press all letters'), 1-back, and 2-back. Each subject performed low and high working memory (WM) load fMRI runs, in a counterbalanced order, each lasting 310 seconds. Each run consisted of 12 blocks, each comprising 9 trials. Results: Working memory performances for the N-Back task were significantly worse in TLE compared to controls for both accuracy and reaction time (p=0.03 and p=0.001, respectively). Between group differences using the SPM 12 analysis package revealed that TLE participants exhibited areas of reduced task activation compared to controls (p < 0.05, FWE-corrected), using percent signal change, in dorsolateral premotor cortex, dorsal cingulate, and medial premotor cortex, regions known to be associated with the executive control network. Conclusions: Executive dysfunction can be observed in children with newly diagnosed TLE using both neuropsychological assessment and functional neuroimaging with evidence of a correlation between the two measures. Compared to controls, children with TLE demonstrate reduced activation in the executive control network which correlates with a classic working memory task (a component of executive function) on neuropsychological assessment. Further investigation is warranted to assess potential compensatory mechanisms involved in the cognitive impairment in pediatric TLE. Funding: This research was supported by funding from the Epilepsy Foundation, ID: 336343