Molecular changes induced by novelty exposure

Exposure to novelty around the time of weak training enhances long-term memory (Ballarini et al., 2009). This enhancement is conserved across rodent models to humans (Fenker et al., 2009). It was proposed that synapses have been ‘tagged’ during the weak training and captured later by the strong event, i.e. novelty exposure (Moncada et al., 2007; Lisman et al., 2011). Concurrently, novelty induces dopamine and noradrenaline release in the hippocampus which similarly enhances memories (Moncada et al., 2011; Duszkiewicz et al., 2019). However, the synaptic and molecular changes induced by novelty have been less studied. One experiment found that the phosphorylated cAMP Response Element-Binding Protein (pCREB) in the hippocampus acts as a marker for the detection of novelty in the environment (Moncada and Viola, 2006). Here, we describe the time course of pCREB induction and the expression of other immediate early genes after novelty both, with biochemical and histochemical methods. These results shed light on the transcription programs that are induced to capture potential tags.