Transection of CA3 does not affect memory performance in rats

Longitudinal hippocampal pathways are needed for seizure synchronization, and there is evidence that their transection may abolish seizures. However, the effect of such transection on memory is unknown. In this study, we investigated the effect of transverse CA3 transections on memory function in Sprague–Dawley rats. With a stereotactic knife, a single CA3 transection was made unilaterally (n = 5) or bilaterally (n = 5). Sham surgery was done in another group (n = 4). Morris water maze and novel object recognition tests were started 18 days later and revealed no significant differences between transected animals and controls. Cresyl-violet brain staining confirmed the locations of transections in the CA3 region. We conclude that normal performances in Morris water maze and novel object recognition tests do not appear to require intact transmission throughout the whole length of CA3, supporting the hypothesis that CA3 transections may be used in temporal lobe epilepsy to interrupt seizure circuitry while preserving memory.

Research highlights
► Hippocampal lamellae are believed to be functional units of memory processing.
► Perpendicular cuts in the hippocampus do not seem to affect performance on memory tasks in rats.
► Hippocampal transections may disrupt seizures without interfering with memory processing in humans.