How we build persistent memories: an investigation of memory durability during encoding and a manipulation of early consolidation

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Only a subset of our experiences are remembered while most are forgotten. What determines whether we remember or forget? In two studies, we aimed at predicting memory retention by looking at the initial encoding phase of an association memory task and investigated the influence of catecholamines on memory retention. Both studies employed an item-location paradigm. In the first experiment, we used a subsequent memory paradigm where we additionally differentiated between durable and weak memory persistence. The results revealed that several frontal and temporal areas exhibited increased activation during the encoding of durable in comparison to weak memories, including the fusiform gyrus, inferior frontal gyrus, superior frontal gyrus, and left lateral orbitofrontal cortex. Furthermore, increased connectivity during encoding between the inferior frontal gyrus and the posterior cingulate cortex was predictive of durable memory retention. All in all, these areas have shown to be crucially involved in successful encoding, revealing stronger activation in a specific set of regions that lead to durable memories. In our second experiment, we explored the influence of methylphenidate on memory retention during the consolidation phase in a double blind, placebo-controlled study. The results revealed no significant difference between groups on memory retention or reaction times. A significant main effect between treatment groups of systolic and diastolic blood pressure and a significant interaction between treatment group and time of heart rate measures was found. To our knowledge, this was the first study to look into the effects of methylphenidate on memory retention during the consolidation phase. Overall, we investigated the neural correlates of durable memory formation during encoding and the facilitation of memory retention during early consolidation. Future studies should focus on integrating findings on a systems and molecular level to adequately assess predictors for durable memories.
Faculteit der Sociale Wetenschappen