Delayed intensive acquisition training alleviates the lesion-induced place learning deficits after fimbria–fornix transection in the rat

Abstract

This study evaluates the effects of two learning paradigms, intensive vs. baseline, on the posttraumatic acquisition of a water maze based place learning task. Rats were subjected either to a control operation (Sham) or to a fimbria–fornix (FF) transection, which renders the hippocampus dysfunctional and disrupts the acquisition of allocentric place learning. All animals were administered 30 post-lesion acquisition sessions, which spanned either 10 or 30days. The acquisition period was followed by a 7day pause after which a retention probe was administered. The lesioned animals were divided into 3 groups: i) Baseline Acquisition Paradigm (BAP) once daily for 30days starting 1week post-surgery; ii) Early Intensive Acquisition Paradigm (EIAP) 3 times daily for 10days starting 1week post-surgery; and iii) Late Intensive Acquisition Paradigm (LIAP) 3 times daily for 10days starting 3weeks post-surgery. Within the control animals, one group followed the schedule of BAP, and one group followed the schedule of Intensive Acquisition Paradigm (IAP). All lesioned animals showed an impaired task acquisition. LIAP was beneficial in FF animals, in that it led to a better acquisition of the place learning task than the two other acquisition paradigms. The FF/EIAP group did not show improved acquisition compared to the FF/BAP group. The control animals were not differentially affected by the two learning schedules. The findings have implications for cognitive rehabilitation after brain injury and support the assumption that intensive treatment can lead to an improved learning, even when the neural structures underlying such a process are compromised. However, the timing of intensive treatment needs to be considered further.