Abstracts

Rationale: In addition to memory impairments, deficits in executive functioning are common in individuals with temporal lobe epilepsy (TLE), including impairments in attention, abstraction, and problem-solving ability. Functional neuroimaging studies have found that frontostriatal circuits are critical for executive functioning. Using diffusion tractography, the current study aims to test the hypothesis that the strength of frontostriatal connections are linked to executive functioning in TLE. Methods: Nine left TLE subjects (age 37.7 /- 4.0 yrs [mean /- SEM]) underwent 3 Tesla MRI scanning including high resolution DTI (64 non-collinear directions, b value = 800 s/mm2) and T1-weighted MP-Rage scans (sense coils 2.4, TR 8.4 ms, TE 3.7 ms) as well as Trails Making Tests. DTI tractography was performed using FSL (http://www.fmrib.ox.ac.uk/fsl/) to determine the relative strength of connections between the caudate nucleus and four prefrontal regions (dorsal prefrontal, ventrolateral, anterior cingulate, and lateral orbitofrontal cortex) in each hemisphere. First, caudate and prefrontal regions were segmented using Freesurfer (http://surfer.nmr.mgh.harvard.edu/). Second, these segmented regions were registered to the FA map generated in FSL using FLIRT. Third, probabilistic tractography was performed to assess for mean percent of connections between the caudate and each prefrontal region. Finally, statistical testing for correlations between mean percent of connections of in each prefrontal region and Trails A, B scores was performed using Spearmans rho and corrected for multiple comparisons (Bonferoni corrections, p <0.05/8 = 0.006).