Effects of an acute seizure on associative learning and memory.

Past studies have demonstrated that inducing several seizures or continuous seizures in neonatal or adult rats results in impairments in learning and memory. The impact of a single acute seizure on learning and memory has not been investigated in mice. In this study, we exposed adult 129SvEvTac mice to the inhalant flurothyl until a behavioral seizure was induced. Our study consisted of 4 experiments where we examined the effect of one seizure before or after delay fear conditioning. We also included a separate cohort of animals that was tested in the open field after a seizure to rule out changes in locomotor activity influencing the results of memory tests. Mice that had experienced a single seizure 1h, but not 6h, prior to training showed a significant impairment in associative conditioning to the conditioned stimulus when compared with controls 24h later. There were no differences in freezing one day later for animals that experienced a single seizure 1h after associative learning. We also found that an acute seizure reduced activity levels in an open-field test 2h but not 24h later. These findings suggest that an acute seizure occurring immediately before learning can have an effect on the recall of events occurring shortly after that seizure. In contrast, an acute seizure occurring shortly after learning appears to have little or no effect on long-term memory. These findings have implications for understanding the acute effects of seizures on the acquisition of new knowledge.