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.
Highlights
Specific odors can induce autobiographical memories (AM-odor), which are accompanied by the visual experience of a spatial and emotional scene, feelings of “being brought back in time” to a moment in the past, heightened emotional arousal, and the sensation of comfort (Willander and Larsson, 2006)
An increased level of memory retrieval and feeling of being “brought back in time” accompanied activity in the left posterior orbitofrontal cortex (POFC) and left fusiform gyrus. Subjective feelings such as the vividness of the memory and degree of comfort impacted the level of left fusiform gyrus and left POFC activation
Our path model suggested that the strength of the memory and emotions elicited by the odorinduced autobiographical memory, which was associated with neural changes in two brain regions, could indirectly impact subjective pleasantness
Summary
Specific odors can induce autobiographical memories (AM-odor), which are accompanied by the visual experience of a spatial and emotional scene, feelings of “being brought back in time” to a moment in the past, heightened emotional arousal, and the sensation of comfort (Willander and Larsson, 2006). Odor Memory and Orbitofrontal-Fusiform Activations retrieval induced by a specific odor can induce powerful visual imagery (Herz, 2004). Brain imaging studies have indicated that AM-odors activate the hippocampus (HI) and amygdala (AMG) (Herz, 2004; Masaoka et al, 2012a), and in younger individuals, the posterior orbitofrontal cortex (POFC) as well (Watanabe et al, 2018). Because olfactory information is directly transmitted to the piriform cortex, AMG, and entorhinal cortex (ENT), that is, centers of emotion and memory processing, olfactory input to these areas is directly associated with individual emotional past experiences (Herz and Cupchik, 1992; Masaoka et al, 2012a). The level of OFC activation elicited by an AM-odor might be associated with the strength of a particular memory, with parallel activation of the para-HI (Watanabe et al, 2018)
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