Understanding memory loss: development of a retrieval-induced forgetting paradigm in rodents to model adaptive forgetting in the mammalian brain?.

FRANCISCO GALLO; FACUNDO MORICI; MAGDALENA MIRANDA; MICHAEL ANDERSON; NOELIA WEISSTAUB; PEDRO BEKINSCHTEIN

Congreso; Federation of Latin American and Caribbean Neuroscience Societies Congress (FALAN 2016).; 2016

Over a century of memory studies have presumed that forgetting was theproduct of passive mechanisms such as decay and interference. In the last twodecades, however, studies on Retrieval-Induced Forgetting (RIF) have demonstratedthe existence of active mechanisms of adaptive forgetting, such as theinhibitory control. Despite this, the lack of animal models precluded the understandingof the neurobiological mechanisms underlying these processes. Usingspontaneous object recognition, we developed a paradigm that allowed us toobserve retrieval-induced forgetting in rats. We have shown that forgetting anitem associated with a particular context occurs under conditions which causecompetition between memory traces (two pairs of objects that share a contextas an evocation cue). We used local pharmacological inactivation to show thatthis kind of forgetting requires the activity of the medial prefrontal cortex(mPFC) in rats; structure homologous to the human dorsolateral prefrontalcortex (DLPFC). By using c-Fos imaging, we also observed that mPFC activationby retrieval practice occurs only during the rst practice sessions, providing evidencethat, as for humans, forgetting is adaptive also for rats. These results areconsistent with the idea that the RIF occurs via a top-down inhibitory controlmechanism exerted by the mPFC on structures where memory traces may bestored.