Abstracts

Rationale: Temporal lobe epilepsy (TLE) is one of the most common epileptic syndromes of focal epilepsy in adults. TLE patients often suffer from cognitive deficits and progressive memory impairments, especially with hippocampal pathology. Hippocampus and medial prefrontal cortex (MPFC) are known to play important roles in cognitive functions, especially memory processing. In this study, we investigated the functional connectivity between medial temporal lobe (MTL) and MPFC, and its relationship with memory impairments in TLE patients. Methods: Resting state functional magnetic resonance imaging (rs-fMRI) and neuropsychological tests were performed on 60 patients with TLE (mean age 42.17 12.41 years) and 30 healthy controls (mean 41.47 12.49 years). TLE patients included 31 patients with left TLE and 29 patients with right TLE (mean 39.84 12.98 vs 44.66 11.24 years old). We assessed verbal, nonverbal memory, attention and executive functions, using the Korean version of California Verbal Learning Test (K-CVLT), Rey-Kim Complex Figure Test (RCFT), Boston Naming Test (BNT), Controlled Oral Word Association Test (COWAT), and Stroop test. In addition, we analyzed seed-based functional connectivity in left MTL-MPFC and right MTL-MPFC, using the regions of interest (ROIs) in left/right hippocampus, parahippocampal gyrus and amygdala for left/right MTL seeds, respectively. Also, we examined the correlation analysis between the MTL/MPFC functional connectivity values and various neuropsychological test scores. Results: Compared to healthy controls, TLE patients showed worse performance in various neuropsychological tests including CVLT total (p = 0.0003), CVLT immediate recall (p = 0.0225), CVLT delayed recall (p = 0.0005), RCFT immediate recall (p = 0.0011), RCFT delayed recall (p = 0.0003), COWAT (p = 0.0001), BNT (p = 0.0001), and Stroop test scores (p = 0.0003). Functional connectivity analysis in TLE patients tended to decrease in left MTL-MPFC and right MTL-MPFC compared to controls, but it did not reach statistical significance. Interestingly, average functional connectivity value in left MTL-MPFC was significantly lower in left TLE group when directly compared with right TLE group (p = 0.0138). Furthermore, decreased left MTL-MPFC connectivity in TLE patients was significantly correlated with more severe verbal memory impairment, especially with lower CVLT delayed recall scores (p = 0.0331). Conclusions: As a result, patients with left TLE showed decreased functional interaction in left MTL-MPFC functional connectivity. Moreover, we found that the verbal memory deficits in these patients were significantly correlated with altered functional connectivity in left MTL/MPFC. Overall, these findings support the left MTL-MPFC functional network should have crucial role in verbal memory function. Funding: Supported by grants of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare [H114C1989 to HWL], and of the Basic Science Research Program through the National Research Foundation (NRF) by the Ministry of Science, ICT and future planning, Republic of Korea [2014-R1A2A1A11052103 to HWL and 2015R1C1A1A01052438 to CHP].