Disruptions in effortful recall could lead to difficulties in autobiographical memory (AM), a condition associated with major depressive disorder (MDD).
A recent JAMA Network Open study assessed whether odor vs word cues could prompt memory in MDD patients with deficits in specific AM recall.
Study: Recall of Autobiographical Memories Following Odor vs Verbal Cues Among Adults With Major Depressive Disorder. Image Credit: Elipetit/Shutterstock.com
Background
MDD severely diminishes and limits an individual’s quality of life. A cognitive feature of MDD is difficulty recalling specific AMs. AM is where specific episodic memories are recalled due to general abstract self-knowledge.
Most studies on AM in MDD have used pictures or words to cue memory retrieval. Research has also shown that odor cues could elicit less verbally mediated and more direct responses.
No study has investigated the presence of over-general AM in MDD when odor cues trigger specific episodic recall.
Compared to memories evoked by words, the memories triggered by odors evoke more emotional memories associated with stronger feelings of reliving.
The phenomenon that odors give rise to highly vivid AMs is called the Proust phenomenon. However, the characteristics of odor-cued AMs in the MDD population have not been studied yet.
About the study
This study was conducted at the University of Pittsburgh School of Medicine and used data collected between September 2021 and November 2022.
Both odor cues and word cues were used in a counterbalanced and random order to assess recall of specific AMs. Adults with a primary diagnosis of MDD were recruited as participants.
The main outcome variable was the fraction of odor-cue-driven specific AMs recall compared to word-cued memories. Secondary outcome measures were vividness, arousal, and recall response time for memories cued by odor.
Study findings
It was noted that MDD participants recalled more specific AMs with odor cues than with word cues. This specificity prevailed despite participants' difficulty identifying the odors presented.
Consistent with previous research on MDD patients, participants of this study were able to identify odors 29% of the time. This finding suggests the lack of correlation between AM recall and the identification of odors.
The fact that odor cues evoked such high rates of AM recall lends credence to the view that odor cues activate a more direct recall route than verbally mediated ones.
Odor cues may also be more effective at improving memory in depression because, unlike them, word cues face some constraints from prefontally and verbally mediated processing deficits.
Odor-cued memories were seen to be more vivid and arousing than word-cued memories.
No order association was noted in this within-participant design setting i.e., the order of presentation of word and odor cues was irrelevant. Furthermore, no association was documented between depression severity and memory performance.
These preliminary results suggest that improving autobiographical specificity could lead to a lowering of depressive symptoms.
Future research should try to uncover the underlying mechanisms of odor-cued AMs to test the hypothesis that hippocampal and amygdala activity are augmented by odor cues.
Odor-cued memory-specificity training could offer an affordable way to ensure amygdala activation during positive memory recall.
Future research should also focus on taste cues, as the amygdala directly maps the gustatory cortex. For this reason, taste cues could also bring about an increase in AM specificity.
However, participants may be less willing to engage with such a protocol, and there may be more allergy issues relative to odor cues.
Conclusions
In sum, it was observed that odor cues evoked recall of more specific AMs in participants with MDD relative to word cues.
AMs evoked by odor cues were also more vivid and arousing, lending credence to the Proust phenomenon. This study is expected to motivate further research using larger samples in more diverse settings to explain these associations further.
The key limitation of this study centered around the absence of a healthy control group. Not having a well-identified benchmark made it difficult to make conclusive inferences regarding the occurrence of the overgeneral memory phenomenon in the sample.
However, compared with the healthy population average of recalling specific memories, researchers suggested the possibility of an overgenerality.
A second limitation was the relatively small sample size. While the primary outcome was detected with sufficient power, bigger samples are required to explore other recalled memories' characteristics, such as valence, further.
Finally, the study participants were mainly white females. Although future research should use diverse samples, it must be noted that the sample used here represented the patients with a primary MDD diagnosis.
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