Abstracts

Rationale: Epilepsy may affect cognition, and specific cognitive deficits are associated with different epilepsy syndromes. Patients with temporal lobe epilepsy (TLE) often suffer from impaired memory and language function, and we have previously shown that subjects with TLE are impaired on specific tactile and auditory tasks. In this study we sought to determine if TLE impairs visual information processing and if such impairments may result from anti-epileptic drug (AED) treatment.Methods: A visual frequency discrimination and a luminance discrimination task were administered to 30 subjects with medically intractable unilateral TLE and 27 neurologically normal controls. Both low-level psychophysical tasks were performed at two stimulus durations, short and long. In addition, TLE subjects performed the luminance discrimination task while taking their usual AEDs, and after AED withdrawal during video-EEG monitoring. Each task was completed three times at each stimulus duration, and the mean of the three thresholds was taken as the final psychophysical threshold. In addition to the visual tasks subjects completed the Wechsler Abbreviated Scale of Intelligence. Data were analyzed using a repeated measures ANOVA.Results: There was no significant age or FSIQ difference between groups. Group main effect was non-significant in either task, and the group x duration interaction was also NS. Not surprisingly, in both tasks the main effect of stimulus duration was highly significant (p < 0.001), with better performance at the longer stimulus duration. Therefore, TLE subjects performed as well as controls on both tasks, at both stimulus durations. There was also no difference in performance of the TLE subjects on the luminance discrimination task at high and low AED levels.Conclusions: A temporal lobe seizure focus does not impair performance on low-level visual psychophysical tasks, in contrast to its effect on selected auditory and tactile tasks. This suggests that TLE does not significantly disrupt visual processing networks. Furthermore, performance is unaffected by AED treatment, even at relatively high doses, indicating that these medications do not cause a non-specific disruption of visual function.