The effects of temporal lobe epilepsy on scene encoding

Abstract

Forty-four patients with temporal lobe epilepsy (TLE) (25 left) and 40 healthy control participants performed a complex visual scene-encoding fMRI task in a 4-T Varian scanner. Healthy controls and left temporal lobe epilepsy (LTLE) patients demonstrated symmetric activation during scene encoding. In contrast, right temporal lobe (RTLE) patients demonstrated left lateralization of scene encoding which differed significantly from healthy controls and LTLE patients (all p≤.05). Lateralization of scene encoding to the right hemisphere among LTLE patients was associated with inferior verbal memory performance as measured by neuropsychological testing (WMS-III Logical Memory Immediate, p=0.049; WMS-III Paired Associates Immediate, p=0.036; WMS-III Paired Associates Delayed, p=0.047). In RTLE patients, left lateralization of scene encoding was associated with lower visuospatial memory performance (BVRT, p=0.043) but improved verbal memory performance (WMS-III Word List, p=0.049). These findings indicate that, despite the negative effects of epilepsy, memory functioning is better supported by the affected hemisphere than the hemisphere contralateral to the seizure focus.