A non-invasive olfactory bulb measure dissociates Parkinson's patients from healthy controls and discloses disease duration

2021. Behzad Iravani (et al.). npj Parkinson's Disease 7 (1)

Article

Olfactory dysfunction is a prevalent non-motor symptom of Parkinson’s disease (PD). This dysfunction is a result of neurodegeneration within the olfactory bulb (OB), the first processing area of the central olfactory system, and commonly precedes the characteristic motor symptoms in PD by several years. Functional measurements of the OB could therefore potentially be used as an early biomarker for PD. Here, we used a non-invasive method, so-called electrobulbogram (EBG), to measure OB function in PD and age-matched healthy controls to assess whether EBG measures can dissociate PDs from controls. We estimated the spectrogram of the EBG signal during exposure to odor in PD (n = 20) and age-matched controls (n = 18) as well as identified differentiating patterns of odor-related synchronization in the gamma, beta, and theta frequency bands. Moreover, we assessed if these PD-EBG components could dissociate PD from control as well as their relationship with PD characteristics. We identified six EBG components during the initial and later stages of odor processing which dissociated PD from controls with 90% sensitivity and 100% specificity with links to PD characteristics. These PD-EBG components were related to medication, disease duration, and severity, as well as clinical odor identification performance. These findings support using EBG as a tool to experimentally assess PD interventions, potentially aid diagnosis, and the potential development of EBG into an early biomarker for PD.

No Evidence That Hormonal Contraceptives Affect Chemosensory Perception

2021. Martin Schaefer (et al.). i-Perception 12 (1), 1-14

Article

The use of oral contraceptives (OC) in the form of a hormonal pill has been widespread for decades. Despite its popularity and long-time use, there is still much ambiguity and anecdotal reports about a range of potential side effects. Here, we addressed the potential effect of OC use on chemosensory perception. Previous research has almost exclusively focused on olfaction, but we expanded this to the trigeminal system and the sense of taste. We used Bayesian statistics to compare the olfactory, trigeminal, and taste detection abilities between a group of 34 normal cycling women and a group of 26 women using OC. Our results indicated that odor, trigeminal, and taste thresholds were not affected by the use of OC. Moreover, neither odor perception, nor taste perception was affected; all with Bayes factors consistently favoring the null hypothesis. The only exception to these results was odor identification where Bayes factors indicated inconclusive evidence. We conclude that effects of OC use on chemosensory perception are unlikely, and if present, likely are of no to little behavioral relevance.

Odor identity can be extracted from the reciprocal connectivity between olfactory bulb and piriform cortex in humans

2021. Behzad Iravani (et al.). NeuroImage 237

Article

Neuronal oscillations route external and internal information across brain regions. In the olfactory system, the two central nodes -the olfactory bulb (OB) and the piriform cortex (PC) -communicate with each other via neural oscillations to shape the olfactory percept. Communication between these nodes have been well characterized in non-human animals but less is known about their role in the human olfactory system. Using a recently developed and validated EEG-based method to extract signals from the OB and PC sources, we show in healthy human participants that there is a bottom-up information flow from the OB to the PC in the beta and gamma frequency bands, while top-down information from the PC to the OB is facilitated by delta and theta oscillations. Importantly, we demonstrate that there was enough information to decipher odor identity above chance from the low gamma in the OB-PC oscillatory circuit as early as 100 ms after odor onset. These data further our understanding of the critical role of bidirectional information flow in human sensory systems to produce perception. However, future studies are needed to determine what specific odor information is extracted and communicated in the information exchange.

The human olfactory bulb processes odor valence representation and cues motor avoidance behavior

2021. Behzad Iravani (et al.). Proceedings of the National Academy of Sciences of the United States of America 118 (42)

Article

Determining the valence of an odor to guide rapid approach–avoidance behavior is thought to be one of the core tasks of the olfactory system, and yet little is known of the initial neural mechanisms supporting this process or of its subsequent behavioral manifestation in humans. In two experiments, we measured the functional processing of odor valence perception in the human olfactory bulb (OB)—the first processing stage of the olfactory system—using a noninvasive method as well as assessed the subsequent motor avoidance response. We demonstrate that odor valence perception is associated with both gamma and beta activity in the human OB. Moreover, we show that negative, but not positive, odors initiate an early beta response in the OB, a response that is linked to a preparatory neural motor response in the motor cortex. Finally, in a separate experiment, we show that negative odors trigger a full-body motor avoidance response, manifested as a rapid leaning away from the odor, within the time period predicted by the OB results. Taken together, these results demonstrate that the human OB processes odor valence in a sequential manner in both the gamma and beta frequency bands and suggest that rapid processing of unpleasant odors in the OB might underlie rapid approach–avoidance decisions.

Wine Experts' Recognition of Wine Odors Is Not Verbally Mediated

2021. Ilja Croijmans (et al.). Journal of experimental psychology. General 150 (3), 545-559

Article

Experts have better memory for items within their domain of expertise. Critically, this does not depend on more efficient use of language. However, this conclusion is based mainly on findings from experts in visual and auditory domains. Olfactory experts constitute an interesting potential counterexample since language has been implicated to be critically involved in odor memory in previous studies. We examined the role language plays in odor recognition memory for wine experts, who typically display better wine odor memory than novices and who are also able to name odors better than lay people. This suggests wine experts' superior recognition memory for odors may be verbally mediated. In 2 experiments, recognition memory for wine odors, wine-related odors, and common odors was tested in wine experts and novices. The use of language was manipulated in Experiment 1 with an overt naming versus no-naming condition, and in Experiment 2, with a verbal interference task inhibiting covert verbalization. Across the two experiments the results showed wine experts have better recognition memory for wines, but not for wine-related or common odors, indicating their memory advantage is expertise specific. Critically, this effect was not verbally mediated, as there was no relationship between experts' ability to name wines and their memory for them. Likewise, directly inhibiting online use of verbalization did not affect memory for wine odors in experts. In sum, once expertise has been acquired, language does not play a causal role in recognition memory for odors.

Expertise Shapes Multimodal Imagery for Wine

2020. Ilja Croijmans (et al.). Cognitive science 44 (5)

Article

Although taste and smell seem hard to imagine, some people nevertheless report vivid imagery in these sensory modalities. We investigate whether experts are better able to imagine smells and tastes because they have learned the ability, or whether they are better imaginers in the first place, and so become experts. To test this, we first compared a group of wine experts to yoked novices using a battery of questionnaires. We show for the first time that experts report greater vividness of wine imagery, with no difference in vividness across sensory modalities. In contrast, novices had more vivid color imagery than taste or odor imagery for wines. Experts and novices did not differ on other vividness of imagery measures, suggesting a domain-specific effect of expertise. Critically, in a second study, we followed a group of students commencing a wine course and a group of matched control participants. Students and controls did not differ before the course, but after the wine course students reported more vivid wine imagery. We provide evidence that expertise improves imagery, exemplifying the extent of plasticity of cognition underlying the chemical senses.

Putting action into testing

2020. Veit Kubik (et al.). Quarterly Journal of Experimental Psychology 73 (12), 2093-2105

Article

Retrieval practice improves long-term retention. However, it is currently debated if this testing effect can be further enhanced by overtly producing recalled responses. We addressed this issue using a standard cued-recall testing-effect paradigm with verb–noun action phrases (e.g., water the plant) to prompt motor actions as a specifically powerful response format of recall. We then tested whether motorically performing the recalled verb targets (e.g., ?–the plant) during an initial recall test (enacted retrieval) led to better long-term retention than silently retrieving them (covert retrieval) or restudying the complete verb–noun phrases (restudy). The results demonstrated a direct testing effect, in that long-term retention was enhanced for covert retrieval practice compared to restudy practice. Critically, enactment during retrieval further improved long-term retention beyond the effect of covert memory retrieval, both in a congruent noun-cued recall test after 1 week (Experiment 1) and in an incongruent verb-cued recall test of nouns after 2 weeks (Experiment 2). This finding suggests that successful memory retrieval and ensuing enactment contribute to future memory performance in parts via different mechanisms.

Relationship Between Odor Intensity Estimates and COVID-19 Prevalence Prediction in a Swedish Population

2020. Behzad Iravani (et al.). Chemical Senses 45 (6), 449-456

Article

In response to the coronavirus disease 2019 (COVID-19) pandemic, countries have implemented various strategies to reduce and slow the spread of the disease in the general population. For countries that have implemented restrictions on its population in a stepwise manner, monitoring of COVID-19 prevalence is of importance to guide the decision on when to impose new, or when to abolish old, restrictions. We are here determining whether measures of odor intensity in a large sample can serve as one such measure. Online measures of how intense common household odors are perceived and symptoms of COVID-19 were collected from 2440 Swedes. Average odor intensity ratings were then compared to predicted COVID-19 population prevalence over time in the Swedish population and were found to closely track each other (r = -0.83). Moreover, we found that there was a large difference in rated intensity between individuals with and without COVID-19 symptoms and the number of symptoms was related to odor intensity ratings. Finally, we found that individuals progressing from reporting no symptoms to subsequently reporting COVID-19 symptoms demonstrated a large drop in olfactory performance. These data suggest that measures of odor intensity, if obtained in a large and representative sample, can be used as an indicator of COVID-19 disease in the general population. Importantly, this simple measure could easily be implemented in countries without widespread access to COVID-19 testing or implemented as a fast early response before widespread testing can be facilitated.

Non-invasive recording from the human olfactory bulb

2020. Behzad Iravani (et al.). Nature Communications 11 (1)

Article

Measures of neural processing can be obtained non-invasively from all areas of the human brain but one, the olfactory bulb. Here, the authors show that signals obtained from EEG electrodes at the nasal bridge represent responses from the human olfactory bulb, the so-called Electrobulbogram. Current non-invasive neuroimaging methods can assess neural activity in all areas of the human brain but the olfactory bulb (OB). The OB has been suggested to fulfill a role comparable to that of V1 and the thalamus in the visual system and have been closely linked to a wide range of olfactory tasks and neuropathologies. Here we present a method for non-invasive recording of signals from the human OB with millisecond precision. We demonstrate that signals obtained via recordings from EEG electrodes at the nasal bridge represent responses from the human olfactory bulb - recordings we term Electrobulbogram (EBG). The EBG will aid future olfactory-related translational work but can also potentially be implemented as an everyday clinical tool to detect pathology-related changes in human central olfactory processing in neurodegenerative diseases. In conclusion, the EBG is localized to the OB, is reliable, and follows response patterns demonstrated in non-human animal models.

The reminiscence bump is blind to blindness

2020. Stina Cornell Kärnekull (et al.). Consciousness and Cognition 78

Article

The reminiscence bump is the disproportionally high reporting of autobiographical memories from adolescence and early adulthood and is typically observed when memories are evoked by cues, such as words, pictures, and sounds. However, when odors are used the bump shifts to early childhood. Although these findings indicate that sensory modality affects the bump, the influence of the individual's sensory function on the reminiscence bumps is unknown. We examined the reminiscence bumps of sound- and odor-evoked autobiographical memories of early blind and sighted individuals, since early blindness implies considerable effects on sensory experience. Despite differences in sensory experience between blind and sighted individuals, the groups displayed similar age distributions of both sound- and odor-evoked memories. The auditory bump spanned the first two decades of life, whereas the olfactory bump was once again found in early childhood. These results demonstrate that the reminiscence bumps are robust to fundamental differences in sensory experience.

Artin ArshamianResearcher

Publications

A non-invasive olfactory bulb measure dissociates Parkinson's patients from healthy controls and discloses disease duration

No Evidence That Hormonal Contraceptives Affect Chemosensory Perception

Odor identity can be extracted from the reciprocal connectivity between olfactory bulb and piriform cortex in humans

The human olfactory bulb processes odor valence representation and cues motor avoidance behavior

Wine Experts' Recognition of Wine Odors Is Not Verbally Mediated

Expertise Shapes Multimodal Imagery for Wine

Putting action into testing

Relationship Between Odor Intensity Estimates and COVID-19 Prevalence Prediction in a Swedish Population

Non-invasive recording from the human olfactory bulb

The reminiscence bump is blind to blindness