Abstracts

Rationale: This research focuses on the investigation of spatial memory impairment in Temporal Lobe Epilepsy (TLE) and the associated underlying pathological cause. Depleted and abnormal development of adult stem cell derived new neurons in the hippocampus has been correlated with performance in spatial memory tasks in animals. Recently, research has highlighted a specific memory retention impairment in animals and humans with TLE, known as accelerated forgetting. We aimed to investigate accelerated forgetting in spatial navigation tasks in humans with selective unilateral Amydalo-hippocampectomy, and animals with kainite induced chronic TLE, and the associated role of neurogenesis. Methods: Patients with unilateral selective Amydalo-hippocampectomies were assessed using a Virtual Morris Water Maze. They were tested over sessions spaced 3-6 weeks apart. Animals with chronic kainate-induced TLE were trained using a Morris Water Maze. One group of animals were tested immediately, while another was tested ten days later to assess for accelerated forgetting. Animal tissue was removed and processed for immuno staining with antibodies to BrdU, Doublecortin and NeuN. Results: Kainate animals had depleted neurogenesis with altered dendritic arborisation, and a higher percentage of cells growing ectopically compared to the controls. It was found that both kainate treated animals and humans with right sided selective hippocampal resection were able to learn the task after extensive training, but showed significant impairment in the retention trials compared to control subjects. Conclusions: This research provides evidence of a hippocampal origin, involving the process of neurogenesis, for accelerated forgetting in spatial tasks.