An acute seizure prior to memory reactivation transiently impairs associative memory performance in C57BL/6J mice

Abstract

Memory deficits significantly decrease an individual's quality of life and are a pervasive comorbidity of epilepsy. Despite the various distinct processes of memory, the majority of epilepsy research has focused on seizures during the encoding phase of memory, therefore the effects of a seizure on other memory processes is relatively unknown. In the present study, we investigated how a single seizure affects memory reactivation in C57BL/6J adult mice using an associative conditioning paradigm. Initially, mice were trained to associate a tone (conditioned stimulus), with the presence of a shock (unconditioned stimulus). Flurothyl was then administered 1 h before, 1 h after, or 6 h before a memory reactivation trial. The learned association was then assessed by presenting a conditioned stimulus in a new context 24 h or 1 wk after memory reactivation. We found that mice receiving a seizure 1 h prior to reactivation exhibited a deficit in memory 24 h later but not 1 wk later. When mice were administered a seizure 6 h before or 1 h after reactivation, there were no differences in memory between seizure and control animals. Altogether, our study indicates that an acute seizure during memory reactivation leads to a temporary deficit in associative memory in adult mice. These findings suggest that the cognitive impact of a seizure may depend on the timing of the seizure relative to the memory process that is active.