Neurogenesis-mediated forgetting minimizes proactive interference

Abstract

Established memories may interfere with the encoding of new memories, particularly when existing and new memories overlap in content. By manipulating levels of hippocampal neurogenesis, here we show that neurogenesis regulates this form of proactive interference. Increasing hippocampal neurogenesis weakens existing memories and, in doing so, facilitates the encoding of new, conflicting (but not non-conflicting) information in mice. Conversely, decreasing neurogenesis stabilizes existing memories, and impedes the encoding of new, conflicting information. These results suggest that reduced proactive interference is an adaptive benefit of neurogenesis-induced forgetting.

Adult hippocampal neurogenesis and cognitive flexibility — linking memory and mood

“…In addition to pattern integration and pattern separation during memory encoding, neurogenesis has also been proposed to promote the clearance of previously established memories 100,101 . This post-encoding memory erasure may act concurrently with pattern separation to reduce proactive interference, a process by which previously learned information impedes the learning of new information that has a highly similar content.…”

“…In accordance with the memory clearance hypothesis 78,100 , neurogenesis may promote the erasure of previously learned associations; for example, where a safety platform is hidden in the Morris water maze task. ‘Forgetting’ the old association may consequently facilitate the learning of novel associations, such as the new location of the safety platform 101 (FIG. 2).…”

Adult Neurogenesis in the Songbird: Region-Specific Contributions of New Neurons to Behavioral Plasticity and Stability

“…The distinctions among various permutations of this idea lie largely in the details of memory encoding [Hunsaker and Kesner, 2013;Hersman et al, 2015]. The other idea is that new neurons lead to forgetting of older memories, which may be necessary to permit new learning, and thus is equally adaptive [Frankland et al, 2013;Epp et al, 2016]. Naturally, the two ideas are not incompatible and may even be complementary.…”

“…New neurons may confer plasticity or sensitivity via increased excitability and lowered firing thresholds, due both to smaller membrane surface area [Schmidt-Hieber et al, 2004;Ge et al, 2007] and an excitable response to GABA [Toni and Schinder, 2015]. Regardless, a common supposition is that either via properties inherent in the cells themselves and/or via addition of new nodes to a circuit, new neurons provide increased behavioral plasticity permissive for learning new [Ikrar et al, 2013;Johnston et al, 2016] and/or overwriting old [Yau et al, 2015;Epp et al, 2016] memories. The goal of this review is to explore whether new neurons may contribute to functions other than learning or behavioral plasticity when incorporated into brain regions outside of the hippocampus and olfactory bulb.…”

Neurogenesis in Cancun: where science meets the sea

“…He provided information on the top-down control of adult-born neuron activity to encode hedonic values, as well as interesting new data on a possible connection between the microbiome and adult neurogenesis. Paul Frankland (Hospital for Sick Children, Toronto, Canada) talked about the role of hippocampal neurogenesis in forgetting and minimizing proactive interference (Epp et al, 2016). In both Lledo's and Frankland's talks, optogenetic or chemogenetic approaches in awake mice were employed to corroborate and build upon previous findings with regard to the functional roles of adult-born neuron in learning and memory.…”