Intrusive memories as conditioned responses to odours: A critical test of cue-specificity

Intrusive memories, a hallmark of trauma-related psychopathology, have been conceptualised as conditioned responses (CRs) to trauma-related cues. Yet, some real-world and laboratory findings challenge whether such memories are indeed a result of a neutral conditioned stimulus (CS) signaling a distressing outcome (unconditioned stimulus). Understanding which associative learning processes contribute to intrusive memories would help optimise treatments. The present study critically tested the conditioning account of intrusive memories by examining their cue-specificity. Undergraduates (N = 91) completed a within-subject conditioned-film paradigm using neutral odours as CSs (CS1+, CS2+, CS-) paired with three film types depicting accidents/injury, violence/threat, or neutral scenes. Participants recorded intrusive memories in daily life for eight days. To elicit cue-specific intrusions, participants sprayed an odour (CS2+) on their clothes either upon leaving the lab (Day 0, n = 45) or three days later at home (Day 3, n = 46). On Day 7, participants completed a task in the lab assessing intrusive memories cued by the CS odours. Although exposure to the odour cue on Day 3 produced more intrusive memories than a control odour, these were not selective for the associated film type. In the lab, partial cue-specificity emerged: one conditioned odour (CS1+) elicited mostly cue-specific intrusions, whereas the other (CS2+) evoked intrusions from both distressing film types. Explicit memory for the contingencies enhanced cue specificity in the lab, but not in daily life. These findings call into question the conceptualisation of intrusive memories as CRs, suggesting that associative learning contributes to intrusive memories, but that cue-specificity may be context dependent.