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Mignot C, Weise S, Podlesek D, Leonhardt G, Bensafi M, Hummel T. What do brain oscillations tell about the human sense of smell? J Neurosci Res 2024; 102:e25335. [PMID: 38634155 DOI: 10.1002/jnr.25335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 04/04/2024] [Accepted: 04/06/2024] [Indexed: 04/19/2024]
Abstract
Brain activity may manifest itself as oscillations which are repetitive rhythms of neuronal firing. These local field potentials can be measured via intracranial electroencephalography (iEEG). This review focuses on iEEG used to map human brain structures involved in olfaction. After presenting the methodology of the review, a summary of the brain structures involved in olfaction is given, followed by a review of the literature on human olfactory oscillations in different contexts. A single case is provided as an illustration of the olfactory oscillations. Overall, the timing and sequence of oscillations found in the different structures of the olfactory system seem to play an important role for olfactory perception.
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Affiliation(s)
- Coralie Mignot
- Smell & Taste Clinic, Department of Otorhinolaryngology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Susanne Weise
- Smell & Taste Clinic, Department of Otorhinolaryngology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Dino Podlesek
- Department of Neurosurgery, Technische Universität Dresden, Dresden, Germany
| | - Georg Leonhardt
- Department of Neurosurgery, Technische Universität Dresden, Dresden, Germany
| | - Moustafa Bensafi
- Lyon Neuroscience Research Center, CNRS-INSERM-University Claude Bernard of Lyon, CH Le Vinatier, Lyon, France
| | - Thomas Hummel
- Smell & Taste Clinic, Department of Otorhinolaryngology, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
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Iravani B, Frasnelli J, Arshamian A, Lundström JN. Metabolic state modulates neural processing of odors in the human olfactory bulb. Biol Psychol 2024; 187:108770. [PMID: 38460755 DOI: 10.1016/j.biopsycho.2024.108770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 03/04/2024] [Accepted: 03/05/2024] [Indexed: 03/11/2024]
Abstract
The olfactory and endocrine systems have recently been shown to reciprocally shape the homeostatic processes of energy intake. As demonstrated in animal models, the individual's metabolic state dynamically modulates how the olfactory bulb process odor stimuli using a range of endocrine signals. Here we aimed to determine whether the neural processing of odors in human olfactory bulb is modulated by metabolic state. Participants were exposed to food-associated odors, in separate sessions being hungry and sated, while neural responses from the olfactory bulb was obtained using electrobulbogram. We found significantly higher gamma power activity (51-100 Hz) in the OB's response to odors during the Hunger compared to Sated condition. Specifically, EBG gamma power were elevated while hungry already at 100 ms after odor onset, thereby suggesting intra-bulbar modulation according to metabolic state. These results demonstrate that, akin to other animal models, hunger state affects OB activity in humans. Moreover, we show that the EBG method has the potential to measure internal metabolic states and, as such, could be used to study specificities in olfactory processing of individuals suffering from pathologies such as obesity or anorexia.
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Affiliation(s)
- Behzad Iravani
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Department of Neurology and Neurological Sciences, Stanford, CA, USA
| | - Johannes Frasnelli
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Department of Anatomy, Université du Québec à Trois-Rivières, Trois-Rivieres, QC, Canada
| | - Artin Arshamian
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Johan N Lundström
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Monell Chemical Senses Center, Philadelphia, PA, USA.
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Dikeçligil GN, Gottfried JA. What Does the Human Olfactory System Do, and How Does It Do It? Annu Rev Psychol 2024; 75:155-181. [PMID: 37788573 DOI: 10.1146/annurev-psych-042023-101155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Historically, the human sense of smell has been regarded as the odd stepchild of the senses, especially compared to the sensory bravado of seeing, touching, and hearing. The idea that the human olfaction has little to contribute to our experience of the world is commonplace, though with the emergence of COVID-19 there has rather been a sea change in this understanding. An ever increasing body of work has convincingly highlighted the keen capabilities of the human nose and the sophistication of the human olfactory system. Here, we provide a concise overview of the neuroscience of human olfaction spanning the last 10-15 years, with focus on the peripheral and central mechanisms that underlie how odor information is processed, packaged, parceled, predicted, and perturbed to serve odor-guided behaviors. We conclude by offering some guideposts for harnessing the next decade of olfactory research in all its shapes and forms.
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Affiliation(s)
| | - Jay A Gottfried
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA; ,
- Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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GoodSmith MS, Wroblewski KE, Schumm LP, McClintock MK, Pinto JM. Association of APOE ε4 Status With Long-term Declines in Odor Sensitivity, Odor Identification, and Cognition in Older US Adults. Neurology 2023; 101:e1341-e1350. [PMID: 37495381 PMCID: PMC10558172 DOI: 10.1212/wnl.0000000000207659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 06/02/2023] [Indexed: 07/28/2023] Open
Abstract
BACKGROUND AND OBJECTIVES The APOE ε4 allele confers susceptibility to faster decline in odor identification and subsequently to Alzheimer disease (AD). Odor identification requires recognizing and naming odors and detecting them (odor sensitivity). Whether APOE ε4 is associated with decline of odor sensitivity and whether such decline serves as a harbinger of cognitive decline and AD remains unclear. We determined whether and when APOE ε4 affects decline in odor sensitivity, odor identification, and cognition in the National Social Life Health and Aging Project (NSHAP). METHODS We used data from NSHAP, a nationally representative survey study of home-dwelling US older adults. Olfaction was measured over time (odor identification in 2005, 2010, and 2015; odor sensitivity in 2010 and 2015; both using validated tests). Cognition was measured with a modified version of the Montreal Cognitive Assessment in 2010 and 2015. Genotyping was performed using DNA samples collected in 2010. Odor sensitivity and identification were compared among APOE ε4 carriers and noncarriers stratified by age. Relationships between APOE ε4, odor sensitivity, odor identification, and cognition were analyzed in cross-section using ordinal logistic regression and longitudinally using mixed-effects models adjusted for confounders. RESULTS Odor sensitivity was measured in 865 respondents, odor identification in 1,156 respondents, and cognition in 864 respondents; all these respondents had genetic data available. Odor sensitivity deficits in APOE ε4 carriers were apparent at ages 65-69 years, whereas odor identification deficits did not appear until ages 75-79 years. Subsequently, odor sensitivity did not decline more rapidly with aging in APOE ε4 carriers compared with that in noncarriers (carrier status and aging interaction: odds ratio [OR] 1.44, 95% CI 0.94-2.19, p = 0.092), whereas odor identification declined more rapidly in carriers (aging 10 years interaction: OR 0.26, 95% CI 0.13-0.52, p < 0.001). As expected, and in parallel to odor identification, cognition declined more rapidly in APOE ε4 carriers (interaction: OR 0.55, 95% CI 0.34-0.89, p = 0.015). DISCUSSION APOE ε4 affects decline of odor sensitivity earlier than odor identification or cognition. Thus, testing odor sensitivity may be useful to predict future impaired cognitive function. Identifying the mechanism underlying these relationships will elucidate the key role of olfaction in neurodegeneration during aging.
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Affiliation(s)
- Matthew S GoodSmith
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL.
| | - Kristen E Wroblewski
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL
| | - L Philip Schumm
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL
| | - Martha K McClintock
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL
| | - Jayant M Pinto
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL
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Kocsis B, Pittman-Polletta B. Neuropsychiatric consequences of COVID-19 related olfactory dysfunction: could non-olfactory cortical-bound inputs from damaged olfactory bulb also contribute to cognitive impairment? Front Neurosci 2023; 17:1164042. [PMID: 37425004 PMCID: PMC10323442 DOI: 10.3389/fnins.2023.1164042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 05/24/2023] [Indexed: 07/11/2023] Open
Affiliation(s)
- Bernat Kocsis
- Department of Psychiatry, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA, United States
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Zhou L, Ran Q, Yi R, Tang H, Zhang Y, Yu T. Glutamatergic Neurons of Piriform Cortex Delay Induction of Inhalational General Anesthesia. FUNDAMENTAL RESEARCH 2023. [DOI: 10.1016/j.fmre.2022.12.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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Farruggia MC, Pellegrino R, Scheinost D. Functional Connectivity of the Chemosenses: A Review. Front Syst Neurosci 2022; 16:865929. [PMID: 35813269 PMCID: PMC9257046 DOI: 10.3389/fnsys.2022.865929] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 05/05/2022] [Indexed: 01/01/2023] Open
Abstract
Functional connectivity approaches have long been used in cognitive neuroscience to establish pathways of communication between and among brain regions. However, the use of these analyses to better understand how the brain processes chemosensory information remains nascent. In this review, we conduct a literature search of all functional connectivity papers of olfaction, gustation, and chemesthesis, with 103 articles discovered in total. These publications largely use approaches of seed-based functional connectivity and psychophysiological interactions, as well as effective connectivity approaches such as Granger Causality, Dynamic Causal Modeling, and Structural Equation Modeling. Regardless of modality, studies largely focus on elucidating neural correlates of stimulus qualities such as identity, pleasantness, and intensity, with task-based paradigms most frequently implemented. We call for further "model free" or data-driven approaches in predictive modeling to craft brain-behavior relationships that are free from a priori hypotheses and not solely based on potentially irreproducible literature. Moreover, we note a relative dearth of resting-state literature, which could be used to better understand chemosensory networks with less influence from motion artifacts induced via gustatory or olfactory paradigms. Finally, we note a lack of genomics data, which could clarify individual and heritable differences in chemosensory perception.
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Affiliation(s)
- Michael C. Farruggia
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT, United States,*Correspondence: Michael C. Farruggia,
| | | | - Dustin Scheinost
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT, United States,Child Study Center, Yale School of Medicine, New Haven, CT, United States,Department of Biomedical Engineering, Yale School of Engineering and Applied Science, New Haven, CT, United States,Department of Radiology & Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States,Wu Tsai Institute, Yale University, New Haven, CT, United States
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Spatiotemporal dynamics of odor representations in the human brain revealed by EEG decoding. Proc Natl Acad Sci U S A 2022; 119:e2114966119. [PMID: 35584113 PMCID: PMC9173780 DOI: 10.1073/pnas.2114966119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
To elucidate when and where in the brain different aspects of odor perception emerge, we decoded odors from an electroencephalogram and associated the results with perception and source activities. The odor information was decoded 100 ms after odor onset at the earliest, with its signal sources estimated in and around the olfactory areas. The neural representation of odor unpleasantness emerged 300 ms after odor onset, followed by pleasantness and perceived quality at 500 ms. During this time, brain regions representing odor information spread rapidly from the olfactory areas to regions associated with emotional, semantic, and memory processing. The results suggested that odor perception emerges through computations in these areas, with different perceptual aspects having different spatiotemporal dynamics. How the human brain translates olfactory inputs into diverse perceptions, from pleasurable floral smells to sickening smells of decay, is one of the fundamental questions in olfaction. To examine how different aspects of olfactory perception emerge in space and time in the human brain, we performed time-resolved multivariate pattern analysis of scalp-recorded electroencephalogram responses to 10 perceptually diverse odors and associated the resulting decoding accuracies with perception and source activities. Mean decoding accuracies of odors exceeded the chance level 100 ms after odor onset and reached maxima at 350 ms. The result suggests that the neural representations of individual odors were maximally separated at 350 ms. Perceptual representations emerged following the decoding peak: unipolar unpleasantness (neutral to unpleasant) from 300 ms, and pleasantness (neutral to pleasant) and perceptual quality (applicability to verbal descriptors such as “fruity” or “flowery”) from 500 ms after odor onset, with all these perceptual representations reaching their maxima after 600 ms. A source estimation showed that the areas representing the odor information, estimated based on the decoding accuracies, were localized in and around the primary and secondary olfactory areas at 100 to 350 ms after odor onset. Odor representations then expanded into larger areas associated with emotional, semantic, and memory processing, with the activities of these later areas being significantly associated with perception. These results suggest that initial odor information coded in the olfactory areas (<350 ms) evolves into their perceptual realizations (300 to >600 ms) through computations in widely distributed cortical regions, with different perceptual aspects having different spatiotemporal dynamics.
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Smell-induced gamma oscillations in human olfactory cortex are required for accurate perception of odor identity. PLoS Biol 2022; 20:e3001509. [PMID: 34986157 PMCID: PMC8765613 DOI: 10.1371/journal.pbio.3001509] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 01/18/2022] [Accepted: 12/08/2021] [Indexed: 11/24/2022] Open
Abstract
Studies of neuronal oscillations have contributed substantial insight into the mechanisms of visual, auditory, and somatosensory perception. However, progress in such research in the human olfactory system has lagged behind. As a result, the electrophysiological properties of the human olfactory system are poorly understood, and, in particular, whether stimulus-driven high-frequency oscillations play a role in odor processing is unknown. Here, we used direct intracranial recordings from human piriform cortex during an odor identification task to show that 3 key oscillatory rhythms are an integral part of the human olfactory cortical response to smell: Odor induces theta, beta, and gamma rhythms in human piriform cortex. We further show that these rhythms have distinct relationships with perceptual behavior. Odor-elicited gamma oscillations occur only during trials in which the odor is accurately perceived, and features of gamma oscillations predict odor identification accuracy, suggesting that they are critical for odor identity perception in humans. We also found that the amplitude of high-frequency oscillations is organized by the phase of low-frequency signals shortly following sniff onset, only when odor is present. Our findings reinforce previous work on theta oscillations, suggest that gamma oscillations in human piriform cortex are important for perception of odor identity, and constitute a robust identification of the characteristic electrophysiological response to smell in the human brain. Future work will determine whether the distinct oscillations we identified reflect distinct perceptual features of odor stimuli. Intracranial recordings from human olfactory cortex reveal a characteristic spectrotemporal response to odors, including theta, beta and gamma oscillations, and show that high-frequency responses are critical for accurate perception of odors.
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Iravani B, Arshamian A, Schaefer M, Svenningsson P, Lundström JN. A non-invasive olfactory bulb measure dissociates Parkinson's patients from healthy controls and discloses disease duration. NPJ Parkinsons Dis 2021; 7:75. [PMID: 34408159 PMCID: PMC8373926 DOI: 10.1038/s41531-021-00220-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 06/22/2021] [Indexed: 11/22/2022] Open
Abstract
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.
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Affiliation(s)
- Behzad Iravani
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | - Artin Arshamian
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Department of Psychology, Stockholm University, Stockholm, Sweden
| | - Martin Schaefer
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Per Svenningsson
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Johan N Lundström
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
- Monell Chemical Senses Center, Philadelphia, PA, USA.
- Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA.
- Stockholm University Brain Imaging Centre, Stockholm University, Stockholm, Sweden.
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