Transection of CA3 does not affect memory performance in rats

Abstract

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. Using 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 (MWM) and Novel object recognition (NOR) tests were started 18 days later revealing 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 performance in MWM and NOR tests does 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.

Gestational protein restriction induces CA3 dendritic atrophy in dorsal hippocampal neurons but does not alter learning and memory performance in adult offspring

“…The functional significance of dendritic remodeling in terms of absolute impact on hippocampus processing has remained elusive. Supporting our data showing no significant MWM score differences despite of reduced dendritic arborization in this pyramidal cell layer, recently, Koubeissi et al (2011) have demonstrated that bilateral cuts of the CA3 dorsal hippocampus layer did not affect MWM scores in rats.…”

Long‐term outcome and neuroradiologic changes after multiple hippocampal transection combined with multiple subpial transection or lesionectomy for temporal lobe epilepsy

“…Intermittent incisions perpendicular to the longitudinal axis of the hippocampal formation from its ventricular surface at 4-to 5-mm intervals without ablation of fimbria are expected to inhibit abnormal longitudinal synchronization and thus abolish epileptic activity, while preserving the intrahippocampal neural circuitry and, ultimately, memory function. 6,7 The seizure outcome of MHT at 1 year after surgery was equivalent to that of temporal lobectomy, and the memory indices were preserved at the preoperative level. 5 Although other groups subsequently reported similar results, 8,9 the long-term outcomes after MHT still remain to be clarified, because of the small patient numbers and the limited periods of follow-up in those studies.…”

“…It is a hippocampal counterpart to multiple subpial transection (MST), which is applied to the neocortices. Intermittent incisions perpendicular to the longitudinal axis of the hippocampal formation from its ventricular surface at 4‐ to 5‐mm intervals without ablation of fimbria are expected to inhibit abnormal longitudinal synchronization and thus abolish epileptic activity, while preserving the intrahippocampal neural circuitry and, ultimately, memory function …”

Transsylvian hippocampal transection for mesial temporal lobe epilepsy: surgical indications, procedure, and postoperative seizure and memory outcomes

“…22,23 Although the concept of HT was a proposed hypothesis, not an accepted doctrine, recent studies have described detailed electrophysiological observations in humans 25 and memory preservation in rat models 12 that support the theory and efficacy of HT. However, in the previous literature, the important processes of the surgery and the depth and extent of transection were ambiguous.…”