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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.

The Proustian memory effect—that fragrances elicit more emotional and evocative memories than other memory cues—is well established. Fragrances also potentiate a variety of psychological states from moods to motivated behavior. Consumer research has shown that pleasant, product-congruent scents enhance product appeal, that products with greater emotional and cognitive involvement are perceived more positively, and that scent can increase recall for product information. However, the effect of Proustian memories on product perception has never been examined. The aim of the present study was to address this issue. An extensive pilot test in which the methods for the main experiment were established was first conducted. The main experiment then tested how a product (body lotion) that varied in fragrance pleasantness and Proustian memory potency was perceived. Data analyses from a nationwide study showed that if the lotion fragrance was perceived as very pleasant, and it evoked potent personal emotional memories, that lotion was liked better and judged to be superior on a variety of functional and emotional attributes than the same lotion whose scent was perceived as equally pleasant but was not experienced as evocative. Our findings demonstrate that it is the personal potency of Proustian memories evoked by a product’s fragrance, more than the hedonic qualities of the scent per se, that drives product perception and has important implications for the development of scented products.

Breathing plays an important role in perception of odors and the experience of emotions. We used the dipole tracing method to analyze brain areas related to odor-induced autobiographical memory and emotions estimated from averaged electroencephalograms triggered by inspiration onset during odor presentation. Odor stimuli were perfumes subjects named that elicited a specific, pleasant and personal memory as well as two pleasant odors for controls. The perfumes induced specific emotional responses during memory retrieval, arousal level of the memory, feelings of pleasantness and a sense of familiarity with the odor. Respiration measurement indicated that tidal volume increased and respiratory frequency decreased during presentation of perfume stimuli, showing a deep and slow breathing pattern. Throughout the olfactory stimulation, electroencephalograms and respiration were simultaneously recorded. In the averaged potentials, low frequency oscillation was phase-locked to inspiration. Dipole analysis showed that perfumes activated more widespread areas of the right parahippocampal cortex and converged in the right amygdala compared to control odors. Slow breathing synchronized with odor-induced autobiographical memory and emotions may be subconsciously stored in the parahippocampal cortex and amygdala.

An important feature of olfactory perception is its dependence on respiratory activity. By inspiration, olfactory information ascends directly to olfactory-related limbic structures. Therefore, every breath with odor molecules activates these limbic areas associated with emotional experience and memory retrieval. We tested whether odors associated with autobiographical memories can trigger pleasant emotional experiences and whether respiration changes during stimulation with these odors. During presentation of odors related to autobiographical memories and control odors, we measured minute ventilation, tidal volume, respiratory frequency, O2 consumption, and end tidal CO2 concentration. Findings showed that autobiographical memory retrieval was associated with increasing tidal volume and decreasing respiratory frequency more than during presentation of control odors. Subjective feelings such as emotional arousal during retrieval of the memory, arousal level of the memory itself, or pleasantness and familiarity toward the odor evoked by autobiographical memory were more specific emotional responses compared with those related to control odors. In addition, high trait anxiety subjects responded with a stronger feeling of being taken back in time and had high arousal levels with tidal volume increases. We discussed assumptions regarding how deep and slow breathing is related to pleasantness and comfortableness of an autobiographical memory.

How can people imagine colors from smelling odors? We assumed that when people can name an odor correctly, they can imagine an appropriate color of the odor source through semantic imagery. The participants smelled 20 everyday odors and for each one chose imagined color from a hue-circle of 24 colors. They also named odors whenever they could. Only 8 odors could be associated with each color-category, and many of the 8 were named easily. However, people also could imagine colors from odors, whether the odors could be named or not. From this we can suggest that people would associate an odor with some inner semantic representations, even if they can't name the odor, then they could imagine colors in accordance with the representations.