Forgetting to remember: biological mechanisms of adaptive forgetting

BEKINSCHTEIN, PEDRO

Congreso; Reunión Anual de la Sociedad Argentina de Fisiología (SAFIS) 2018; 2018

SAIC SAI SAFIS

Neurobiologicalresearch on memory has focused on the mechanisms underlying memory storage,with less attention to forgetting. However, forgetting is a ubiquitous phenomenonthat is actively promoted in many species. How and whether active forgettingmechanisms are driven by adaptive behavior is unknown. Here we show that control processes that enable flexible behavior inmammals promote active forgetting of traces that hinder retrieval of memoriesneeded to guide behavior. Wefound that when rats retrieved their prior experience with an object to guidenew exploration, it significantly reduced their later recognition of otherobjects previously encountered in that environment. Consistent with similarfindings in humans, this retrieval-induced forgetting wascompetition-dependent, cue-independent, long-lasting, and reliant on controlprocesses mediated by the prefrontal cortex: Silencingmedial prefrontal cortex with muscimol selectively abolished the forgettingeffect. cFosimaging revealed that prefrontal control demands declined over repeatedretrievals as competing memories were forgotten, revealing a key adaptivebenefit of forgetting. Occurring in 88% of the 63 rats studied, this findingestablishes an unusually robust model of how active forgetting harmonizes themnemonic ecosystem with behavioral demands, and permits isolation of itscircuit, cellular and molecular mechanisms.