The role of rewarding and novel events in facilitating memory persistence in a separate spatial memory task

Abstract

Many insignificant events in our daily life are forgotten quickly but can be remembered for longer when other memorymodulating events occur before or after them. This phenomenon has been investigated in animal models in a protocol in which weak memories persist longer if exploration in a novel context is introduced around the time of memory encoding. This study aims to understand whether other types of rewarding or novel tasks, such as rewarded learning in a T-maze and novel object recognition, can also be effective memory-modulating events. Rats were trained in a delayed matching-to-place task to encode and retrieve food locations in an event arena. Weak encoding with only one food pellet at the sample location induced memory encoding but forgetting over 24 h. When this same weak encoding was followed by a rewarded task in a T-maze, the memory persisted for 24 h. Moreover, the same persistence of memory over 24 h could be achieved by exploration in a novel box or by a rewarded T-maze task after a "non-rewarded" weak encoding. When the one-pellet weak encoding was followed by novel object exploration, the memory did not persist at 24 h. Together, the results confirm that place encoding is possible without explicit reward, and that rewarded learning in a separate task lacking novelty can be an effective memory-modulating event. The behavioral and neurobiological implications are discussed.

Influence of reward motivation on human declarative memory

“…In the future, projects investigating whether and how novelty exploration, emotional arousal or extrinsic reward may boost long-term memory formation, especially for material that does not inspire curiosity or intrinsic motivation, could help translate the present body of neuroscientific knowledge to practical applications. A first animal demonstration showed that novelty exploration indeed can facilitate consolidation in subsequent declarative memory formation and lead to improved recall 24 h later (Salvetti et al, 2014). Similar effects of novelty exploration in humans, have so far been reported for immediate memory tests (Fenker et al, 2008;Schomaker et al, 2014).…”

Facilitation of fear extinction by novelty depends on dopamine acting on D1-subtype dopamine receptors in hippocampus

“…Novelty enhances the phosphorylation state of CREB in the hippocampus (43) and activates hippocampal MAPKs (44). Salvetti et al (45) showed that novelty presented after weak memory training can promote the memory consolidation of a spatial task.…”

Spatial object recognition memory formation under acute stress

“…Moreover, there are findings suggesting the existence of a similar process operating in LTM formation in humans (Ballarini et al, 2013;Dunsmoor, Murty, Davachi, & Phelps, 2015). Besides OF, other experiences such as objects' exploration in a novel arena, a novel taste, a Morris water maze session, a contextual fear conditioning reminder session, contextual fear conditioning extinction session or a rewarded T-maze task were further described as protein supplier events that promote unrelated memories (Ballarini et al, 2009;Cassini et al, 2013;Dong et al, 2012;Salvetti, Morris, & Wang, 2014). Considering the plethora of data about the modulatory effect on memory processes caused by stress or by the administration of glucocorticoids (Cadle & Zoladz, 2015;Joëls et al, 2006;Sandi & Pinelo-Nava, 2007) we considered that a stressful event could influence unrelated memory formation by providing or competing for protein resources.…”