Odors Associated With Autobiographical Memory Induce Visual Imagination of Emotional Scenes as Well as Orbitofrontal-Fusiform Activation

Abstract

Specific odors can induce memories of the past, especially those associated with autobiographical and episodic memory. Odors associated with autobiographical memories have been found to elicit stronger activation in the orbitofrontal cortex, hippocampus, and parahippocampus compared with odors not linked to personal memories. Here, we examined whether continuous odor stimuli associated with autobiographical memories could activate the above olfactory areas in older adults and speculated regarding whether this odor stimulation could have a protective effect against age-related cognitive decline. Specifically, we used functional magnetic resonance imaging to investigate the relationship between blood oxygen levels in olfactory regions and odor-induced subjective memory retrieval and emotions associated with autobiographical memory in older adults. In our group of healthy older adults, the tested odors induced autobiographical memories that were accompanied by increasing levels of retrieval and the feeling of being “brought back in time.” The strength of the subjective feelings, including vividness of the memory and degree of comfort, impacted activation of the left fusiform gyrus and left posterior orbitofrontal cortex. Further, our path model suggested that the strength of memory retrieval and of the emotions induced by odor-evoked autobiographical memories directly influenced neural changes in the left fusiform gyrus, and impacted left posterior orbitofrontal cortex activation through the left fusiform response.

Role of the amygdala‐medial orbitofrontal relationship in odor recognition in the elderly

“…β-phenyl ethyl alcohol was used for odor stimuli, as in a previous study (Masaoka et al, 2021), which confirmed that the stimuli did not elicit memory retrieval or arousal (i.e., the stimuli were categorized as "normal odors") (Masaoka et al, 2012(Masaoka et al, , 2021. Subjects were requested to breath normally and avoid sniffing behaviors during odor presenta-tion.…”

“…The left posterior OFC has a dominant role in odor memory recognition (Masaoka et al., 2021 ), while the left OFC is dominant in terms of odor‐related emotion processing (Royet et al., 2003 ). In this study, left hemisphere structures including the AMG, ENT, para‐HI, HI were involved in olfactory detection.…”

“…The subjects in this study were a subset of those in previous studies (Iizuka et al., 2021 ; Kubota et al., 2020 ; Masaoka et al., 2021 ) with MRI, olfaction, and cognitive test data obtained in 2020. Older adults without cognitive impairment ( N = 30), as confirmed by two neurologists using the Japanese version of the Montreal Cognitive Assessment (MoCA) (Nasreddine et al., 2005 ), were tested in this study.…”

“…The imaging protocol used in this study was detailed previously (Masaoka et al., 2021 ). After a brief clinical examination, MRI scanning (3‐Tesla Magnetom Trio scanner; Siemens, Erlangen, Germany) was conducted at Ebara Hospital, Tokyo, Japan, between 6 pm and 8 pm on Mondays.…”

Behavioral, neurological, and psychiatric frailty of autobiographical memory

“…During mental travel, not only the event is reconstructed (Conway & Howe, 2022), but also the emotion or affect attached to it (Meconi et al, 2021). That this is the case becomes evident from the results of patients with Urbach–Wiethe disease ( Lipoid proteinosis ), a rare very genetic disease (Rosenberger et al, 2019), which leads to a reduced odor perception (Siebert et al, 2003) and to reduced processing of memories with biological and social significance (El Haj, 2022; Iizuka et al, 2021; Larsson & Willander, 2009; Markowitsch & Staniloiu, 2011b, 2012a, 2012b; Masaoka et al, 2021; Phelps, 2004). We demonstrated this in a patient with Urbach‐Wiethe disease by using a paradigm implying a short, narrated story, supported by a picture show.…”