Learning and memory and its relationship with the lateralization of epileptic focus in subjects with temporal lobe epilepsy

Background : In medial temporal lobe epilepsy (MTLE), previous studies addressing the hemispheric laterality of epileptogenic focus and its relationship with learning and memory processes have reported controversial findings. Objective : To compare the performance of MTLE patients according to the location of the epileptogenic focus on the left (MTLEL) or right temporal lobe (MTLER) on tasks of episodic learning and memory for verbal and visual content. Methods : One hundred patients with MTLEL and one hundred patients with MTLER were tested with the following tasks: the Rey Auditory Verbal Learning Test (RAVLT) and the Logical Memory-WMS-R to evaluate verbal learning and memory; and the Rey Visual Design Learning Test (RVDLT) and the Visual Reproduction-WMS-R to evaluate visual learning and memory. Results : The MTLEL sample showed significantly worse performance on the RAVLT (p < 0.005) and on the Logical Memory tests (p < 0.01) than MTLER subjects. However, there were no significant between-group differences in regard to the visual memory tests. Discussion : Our findings suggest that verbal learning and memory abilities are dependent on the structural and functional integrity of the left temporal lobe, while visual abilities are less dependent on the right temporal lobe.