When does vagal activity benefit to the discrimination of highly overlapping memory traces?

Distinguishing among similar events is indeed crucial to memory. In a dangerous context, this ability may be less essential, whereas in a secure context it may provide an adaptative advantage notably in social situations. Vagal activity as a marker of the individual's adaptation in social engagement contexts might predict the ability to discriminate highly similar memories in an unthreatening context. The present study aims to test the relation between vagal activity and memory discrimination by manipulating the visual distinctiveness of stimuli (high vs. low) in an ecological memory discrimination task with humanoid characters. It was expected that vagal activity support adaptive self-regulatory processes which may be needed only when the memory discrimination is challenging (low distinctiveness between true memory and lure). In a study phase, multiple realistic fictional humanoid characters performed the same action on different objects. The characters could be very similar or very distinct one to each other. Then, during a test phase, the participants had to discriminate whether a displayed character on the screen was exactly matched the one performing the given action on a specific object in the study phase (target). Vagal activity was assessed in undergraduate students (n = 40) before the study phase. Higher vagal activity predicted better memory discrimination performance specifically when the distinctiveness between the lure and target was low. These data extend previous work on vagal activity and memory suggesting that heart-brain interactions represent an adaptive psychophysiological mechanism underlying memory discrimination specifically when it is challenging in an unthreatening context.