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

Olfactory outcomes in skull base surgery

PURPOSE OF REVIEW

This review examines the impact of skull base surgery on olfactory function, a critical yet often overlooked aspect of postoperative quality of life. As surgical techniques continue to evolve, understanding their impact on olfaction is key to optimizing patient outcomes.

RECENT FINDINGS

The relationship between skull base surgery and olfactory function continues to be debated in the literature. With the adoption of transnasal surgical approaches, a significant concern has been its impact on olfaction. Prior studies have shown evidence of olfactory dysfunction following transnasal skull base surgery, though these findings are not universal. A particular area of discussion involves the use of the pedicled nasoseptal flap, which has demonstrated potentially negative short-term olfactory impacts. Additional concerns surround flap design (olfactory strip preservation) and technique of flap harvest (cold knife versus electrocautery). Evidence suggests that olfactory strip preservation may effectively maintain postoperative olfactory performance, while cold knife techniques offer no clear advantage over electrocautery.

SUMMARY

The inconsistencies in the literature underscore the need for standardized, large-scale studies that directly compare surgical techniques to better understand the impact of transnasal skull base surgery on olfaction. This is essential to optimizing surgical outcomes and improving patient quality of life postoperatively.

Neural correlates of olfactory working memory in the human brain

Previous research has revealed that the insula, pallidum, thalamus, hippocampus, middle frontal gyrus, and supplementary motor area are activated during odor memory and that the performance of olfactory working memory is affected by the verbalization of odors. However, the neural mechanisms underlying olfactory working memory and the role of verbalization in olfactory working memory are not fully understood. Twenty-nine participants were enrolled in a study to complete olfactory and visual n-back tasks using high- and low-verbalizability stimuli while undergoing fMRI imaging. The behavioral results showed that the participants achieved greater accuracy in the visual rather than olfactory n-back task. We observed increased activation in the precentral gyrus, superior frontal gyrus, middle frontal gyrus, supplementary motor area, and inferior parietal gyrus during olfactory working memory. Interestingly, decreased activation was observed in the olfactory 2-back task versus the 0-back task. Moreover, the left angular gyrus and inferior parietal gyrus were more strongly activated during processing of olfactory working memory using high-verbalizability odors. In conclusion, olfactory working memory engages cross-modal regions to facilitate responses, is involved in the monitoring and manipulation of information during working memory, and boasts a unique activation pattern that is different from that of visual working memory. Semantic information supports the representation of odor information in the working memory system.

A novel olfactory sorting task

BACKGROUND

This study aimed to develop a simple self-administered screening tool for odor memory, which allowed users to self-test their olfactory function repeatedly even at home.

METHODS

One hundred and ten participants were recruited (30 men, age = 50.1 ± 9.9 years; 80 women, age = 47.1 ± 11.5 years); half of them were heathy volunteers, the other half were patients with olfactory dysfunction. Fifty-one healthy participants volunteered for a retest within an interval of a maximum of 14 days. Olfactory function was assessed using the extended Sniffin' Sticks test (SST) comprising tests for odor threshold, identification, and discrimination. All participants received the Novel Olfactory Sorting Task (NOST) which is based on the sorting of 12 matching pairs of odors involving olfactory and cognitive functions. After that, all participants rated questions related to their test performance and the practicability of the test.

RESULTS

Consistent with the previous literature, significant effects of age were found. Results showed an acceptable test-retest reliability and a satisfactory validity of the NOST. The NOST score not only had positive correlations with SST, but also was capable of differentiating severe hyposmia/anosmia from normosmia by the score of 5.5 (sensitivity of 76.2%, specificity of 77.6%).

CONCLUSION

The present study showed the good reliability, validity, and possible clinical usefulness of the NOST. As a self-performed screening test, it can be comprehended and conducted easily, which may provide a quick and simple approach to obtaining a global estimation of olfactory and cognitive functions.

Gender differences in the relationship between neuroticism and odor memory

Given the indications on the relationship between neuroticism and various olfactory functions as well as the emotionality of odor memory, it is surprising that no research so far has investigated whether neuroticism corresponds with odor memory performance. Thus, the purpose of our study was to address this question in the context of gender differences. Participants (73 men) completed the 60-items NEO Five Factor Inventory and participated in 32-items "Test for odor memory". In the separate analyses conducted for men and women, we demonstrated that women outperformed men regarding the number of correct odor recognitions in the odor memory test and had higher neuroticism level than men. Spearman correlation showed further that neuroticism was positively associated with D-prime (R = 0.3, p = .021) and the number of correct odor recognitions in women (R = 0.32, p = .014). This effect was, respectively, moderately (B10 = 5.2) and strongly confirmed using the Bayesian approach (B10 = 8). However, Bonferroni post-hoc correction for multiple comparisons further revealed that in case of neuroticism and the number of hits, as well as D-prime, alpha level was below significance, indicated by p = .006. The correlation between neuroticism level and odor memory performance was significantly higher in women compared to men (Z = 1.8, p = .038), while in case of neuroticism and D-prime, it was on a trend level (Z = 1.5, p = .074). Overall, the present results indicate that neuroticism might be linked to conscious odors' remembering for women, which can be explained by the warning role of odor memory and its connection to limbic structures, as well as by the higher level of neuroticism and odor memory performance in women compared to men.