ODor-evoked Autobiographical Memory in Alzheimer's disease?

Déjà vu and involuntary autobiographical memories as two distinct cases of familiarity in patients with Alzheimer's disease

The continuum between involuntary autobiographical memories and déjà vu, as proposed by Barzykowski and Moulin, can be better defined by considering research on autobiographical retrieval in patients with Alzheimer's disease. Although autobiographical retrieval in patients with Alzheimer's disease can generally be associated with a sense of familiarity, involuntary retrieval can trigger an autonoetic experience of retrieval in these patients.

Behavioral, neurological, and psychiatric frailty of autobiographical memory

Autobiographical-episodic memory is considered to be the most complex of the five long-term memory systems. It is autonoetic, which means, self-reflective, relies on emotional colorization, and needs the features of place and time; it allows mental time traveling. Compared to the other four long-term memory systems-procedural memory, priming, perceptual, and semantic memory-it develops the latest in phylogeny and ontogeny, and is the most vulnerable of the five systems, being easily impaired by brain damage and psychiatric disorders. Furthermore, it is characterized by its fragility and proneness to distortion due to environmental influences and subsequent information. On the brain level, a distinction has to be made between memory encoding and consolidating, memory storage, and memory retrieval. For encoding, structures of the limbic system, with the hippocampus in its center, are crucial, for storage of widespread cortical networks, and for retrieval again a distributed recollection network, in which the prefrontal cortex plays a crucial role, is engaged. Brain damage and psychiatric diseases can lead to what is called "focal retrograde amnesia." In this context, the clinical picture of dissociative or functional or psychogenic amnesia is central, as it may result in autobiographical-emotional amnesia of the total past with the consequence of an impairment of the self as well. The social environment therefore can have a major impact on the brain and on autobiographical-episodic memory processing. This article is categorized under: Psychology > Memory.

Development and validation of the Olfactory Memory Test Battery (OMTB) based on odors with high- and low-verbalizability

BACKGROUND

Odor memory is an important field of clinical research for its distinctive characteristics, which differ from those of other sensory systems. To date, several tests have been implemented for the assessment of odor memory. Despite a range of studies demonstrating the importance of verbal mediation in odor memory, few have distinguished odor memory performance in different odor verbalization levels.

NEW METHOD

We aimed to develop a standardized odor memory test toolbox with one group of odors that are easily verbally identified and the other group of odors that are difficult to identify. The test contained two odor categories (high- and low-verbalizability odors), each consisting of three subtests (short- and long-term memory and working memory).

RESULTS

Satisfactory test-retest reliability and solid validity of the odor recognition and working memory test were shown in both odor categories. Moreover, people scored significantly better with high- than low-verbalizability odors. A negative age effect on odor memory performance was also found.

COMPARISON WITH EXISTING METHODS

No previous odor memory test distinguished odor memory performance in different odor verbalization levels, while the Olfactory Memory Test Battery (OMTB) contains high- and low-verbalizability odors and each category has three subtests.

CONCLUSIONS

The present study indicated the OMTB is a comprehensive assessment of odor memory with good reliability and validity. All subtests can be used separately or in combination with each other according to the clinical and research needs.

Influences of age-related positivity effect on characteristics of odor-evoked autobiographical memories in older Japanese adults

Older adults tend to remember past life events more positively than younger adults. This tendency is the age-related positivity effect. The present study examined whether this effect occurred for odor-evoked autobiographical memories. In total, 317 young and 181 older Japanese participants were asked to recall autobiographical events evoked by odors. Participants then completed the odor-evoked autobiographical memory questionnaire (OEAMQ) to measure the characteristics of the recalled memories. In the results, older participants recalled more positive memories than younger participants. Older participants also rated the OEAMQ subscales higher than the younger participants. Furthermore, there were significant positive correlations between the ratings of odor emotional characteristics and OEAMQ subscales. The age-related positivity effect was observed for odor-evoked autobiographical memories. The emotion aroused by odor played a significant role in some attributes of odor-evoked autobiographical memory. The age-related positivity effect in odor-evoked autobiographical memories has important implications for understanding the cognitive mechanisms of aging in autobiographical memory and olfaction and for applications in well-being and dementia in older adults.

Development of the function of autobiographical memories evoked by odor scale for older Japanese people

Odor-evoked autobiographical memory and related psychological changes have been evaluated based on several factors, such as emotionality, clarity, and re-experience. We developed the Function of Autobiographical Memories Evoked by Odor Scale (FAMOS) for older Japanese people as a new method for comprehensively evaluating the functions of odor-evoked autobiographical memory. We used the diary method; participants were instructed to record the contents of everyday involuntary autobiographical memories triggered by odor and complete the FAMOS. In Study 1, 600 older adults were surveyed to select items for the FAMOS and examine the factor structure. An exploratory factor analysis with PROMAX rotation using the maximum likelihood method resulted in four factors: (1) Evoking positive emotion, (2) Identity, (3) Facilitating communication, and (4) Coping with negative emotion. Sufficient reliability was demonstrated. In Study 2, the FAMOS's validity was examined in 600 older adults. We found significant correlations (Pearson) with the affective valence of odors, the Odor-evoked Autobiographical Memory Questionnaire, and other scales, confirming the validity of the FAMOS. In Study 3, the FAMOS was administered to 600 younger and 600 older adults; generational differences were compared for further validity. Older adults had higher “Evoking positive emotion,” “Identity,” and “Facilitating communication” scores on the FAMOS than younger adults, suggesting a fair degree of reliability and validity of the FAMOS.

Motor Cortex Response to Pleasant Odor Perception and Imagery: The Differential Role of Personality Dimensions and Imagery Ability

Background

Neuroimaging studies have shown a complex pattern of brain activation during perception of a pleasant odor and during its olfactory imagery. To date, little is known regarding changes in motor cortex excitability during these tasks. Bergamot essential oil (BEO) is extensively used in perfumes and cosmetics for its pleasantness. Therefore, to further our understanding of the human sense of smell, this study aimed to investigate the effect of perception and imagery of a pleasant odor (BEO) on motor cortex using Transcranial magnetic stimulation (TMS).

Materials and Methods

We examined the primary motor cortex (M1) excitability during perception of a pleasant odor (BEO) or perception of odorless saline (experiment 1). Furthermore, we tested the effect of olfactory imagery (OI) of BEO on corticospinal excitability (experiment 2). The increase in motor evoked potential (MEP) amplitude was correlated with personality dimensions scores, pleasantness, vividness, and general imagery ability.

Results

The results indicate that the corticospinal excitability changed after both perception and imagery of a pleasant odor (BEO). The correlation analysis shows an association with neuroticism personality trait (experiment 1) and with general olfactory imagery ability (experiment 2).

Conclusion

Both perception of a pleasant odor and its olfactory imagery modulate motor cortex excitability. The enhanced brain activation is affected by specific individual characteristics. Overall, our findings provide physiological evidence for a complex interaction between the olfactory and motor systems.