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Abstract:
When we experience aversive events, these often turn into unwanted memories. Simple reminders can then trigger the involuntary retrieval of these memories. However, prior evidence indicates that we can intentionally suppress the retrieval process to prevent unwanted memories from entering awareness. Such suppression can render memories less vivid and eventually cause forgetting. Here, we test the hypothesis that retrieval suppression weakens memories by compromising their unique neural representations. In an fMRI study, Participants learned associations between reminders and aversive scenes. They were then repeatedly presented with the reminders. For some of these, participants were instructed to suppress the retrieval of the associated scene. Suppression was associated with increased activation in the right dorsolateral prefrontal cortex and a concomitant decrease in hippocampal and parahippocampal activation, a pattern that has been linked to the top-down inhibition of retrieval processes. Critically, we assessed the distributed activity patterns of individual memories (as a proxy for their neural representations) both before and after suppression. Using representational similarity analysis, we could thus track changes in the specificity of the neural representations. We observed that memories became less vivid after suppression, and that a stronger decline in vividness was associated with a greater reduction in the specificity of memory representations in the parahippocampal gyrus. These preliminary results support the hypothesis that suppression deteriorates memories by compromising their unique neural representations.
