Evidence for the standard model, multiple trace theory, or the unified theory?

ABSTRACT There have been two dominating theories for memory consolidation: the standard model (SM) and multiple trace theory (MTT). Whereas lesion studies have largely indicated a waning role for the hippocampus in memory consolidation, and thus have supported SM, findings from neuroimaging studies have produced varying results. Tallman et al. (this issue) argue that this variability may result from confounding factors and that, once these factors are accounted for, their neuroimaging results support SM. They do not, however, consider a third option: the unified theory. Here, we suggest that their findings, along with neurobiochemical and engram cell studies, may better fit this third theory.