Abstracts

Rationale: Epilepsy and stress go hand in hand, but our understanding of this relationship in humans is lacking. Our objective was to assess the neural response to psychosocial stress during fMRI in patients with left temporal lobe epilepsy (LTLE). Methods: Included in the study were 16 LTLE patients who believe that stress is a factor in their seizure control (+S) and 7 who do not (-S). The stress paradigm is based on the Montreal Imaging Stress Task, which increased the stress hormone cortisol during fMRI in a group of healthy subjects (Dedovic et al., 2005). The paradigm consists of (1) a control task in which subjects performed simple subtraction and (2) a stress task in which subjects performed difficult subtraction. Subjects were given positive feedback during the control task and negative feedback during the stress task regardless of performance. MRI data processing (image coregistration, motion correction, spatial normalization), subject- and group-level statistics and visualization were performed using AFNI. General linear model (GLM) was used to assess each subject's neural response to stress by comparing stressful and non-stressful conditions (e.g., difficult vs. easy math problems and negative vs. positive feedback). 1-sample t-tests of GLM results were performed to determine overall patterns of stress-related activation for each group. Results: Both +S and -S groups were more accurate and responded faster for math problems during the control task compared to the stress task (all p<.0005), but the groups did not differ in accuracy or response times for math problems during either task (all p>.12). Increased activation was observed in +S bilaterally in the superior temporal gyrus (STG) in response to difficult compared to easy math problems (corrected p<.05; voxelwise p<.005, cluster >18 voxels). Increased activation also occurred for +S in the left insula and bilaterally in the STG, Brodmann area 39 and posterior cingulate in response to negative feedback compared to positive feedback (corrected p<.05; voxelwise p<.005, cluster >18 voxels). Increased activation to the stressful compared to non-stressful conditions were not observed in the -S group. Conclusions: The +S group showed an overall increased response to stressful task conditions than the -S group despite similar behavioral performance between the two. The increased activation in the +S group to the stressful compared to non-stressful conditions may be part of a compensatory mechanism in order to achieve similar task performance as the -S group. These data support a relationship between the perceived importance of stress in seizure control and brain activation to stressful stimuli among patients with LTLE. Group differences in brain activation patterns may also be related to seizure frequency and requires further study.