Memory Reactivation of Complex Events and Memory Preactivation in Humans

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The hippocampus’ role in memory integration is starting to be understood. However, the exact mechanisms by which existing memories affect newly acquired information remains a matter of debate. We present two approaches to investigate this topic. It has been demonstrated that reactivation during off-line periods is important for memory integration. In previous studies, reactivation of relatively simple stimuli had been investigated but evidence for reactivation of complex events has been lacking. For our first experiment, we use multivariate pattern analyses to assess reactivation of complex events. Analyses of the resting-state blocks of an fMRI memory integration paradigm with complex life-like stimuli showed no evidence for reactivation. We discuss methodological limitations that could explain these results. In rodents it has been found that not only reactivation of previously encoded information, but also preactivation of to be encountered information can be beneficial for memory integration. Contrary to reactivation which refers to experiences in the past, preactivation refers to activation corresponding to events in the future. To date, preactivation had not been assessed in humans. In our second experiment, we present a novel behavioral reaction time paradigm to assess preactivation. The results strongly suggest that humans show preactivation of to be encountered events. For future research, we suggest an fMRI version of the preactivation paradigm used here to shed light on the hippocampus’ role in preactivation.
Faculteit der Sociale Wetenschappen