Development of a retrieval-induced forgetting paradigm in rodents to model adaptive forgetting in the mammalian brain

GALLO FRANCISCO; MORICI JUAN FACUNDO; MIRANDA MAGDALENA; WEISSTAUB NOELIA; BEKINSCHTEIN PEDRO

Congreso; Congreso de la SAN 2016; 2016

Over a century of memory studies have presumed that forgetting was the product of passive mechanisms such as decay and interference. In the last two decades, however, studies on Retrieval-Induced Forgetting (RIF) have demonstrated the existence of active mechanisms of adaptive forgetting, such as the inhibitory control. Despite this, the lack of animal models precluded the understanding of the neurobiological mechanisms underlying these processes. Using spontaneous object recognition, we developed a paradigm that allowed us to observe retrieval-induced forgetting in rats. We have shown that forgetting an item associated with a particular context occurs under conditions which cause competition between memory traces (two pairs of objects that share a context as an evocation cue). We used local pharmacological inactivation to show that this kind of forgetting requires the activity of the medial prefrontal cortex (mPFC) in rats; structure homologous to the human dorsolateral prefrontal cortex (DLPFC). By using c-Fos imaging, we also observed that mPFC activation by retrieval practice occurs only during the first practice sessions, providing evidence that, as for humans, forgetting is adaptive also for rats. These results are consistent with the idea that the RIF occurs via a top-down inhibitory control mechanism exerted by the mPFC on structures where memory traces may be stored.