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Liu D, Lu J, Wei L, Yao M, Yang H, Lv P, Wang H, Zhu Y, Zhu Z, Zhang X, Chen J, Yang QX, Zhang B. Olfactory deficit: a potential functional marker across the Alzheimer's disease continuum. Front Neurosci 2024; 18:1309482. [PMID: 38435057 PMCID: PMC10907997 DOI: 10.3389/fnins.2024.1309482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Accepted: 02/02/2024] [Indexed: 03/05/2024] Open
Abstract
Alzheimer's disease (AD) is a prevalent form of dementia that affects an estimated 32 million individuals globally. Identifying early indicators is vital for screening at-risk populations and implementing timely interventions. At present, there is an urgent need for early and sensitive biomarkers to screen individuals at risk of AD. Among all sensory biomarkers, olfaction is currently one of the most promising indicators for AD. Olfactory dysfunction signifies a decline in the ability to detect, identify, or remember odors. Within the spectrum of AD, impairment in olfactory identification precedes detectable cognitive impairments, including mild cognitive impairment (MCI) and even the stage of subjective cognitive decline (SCD), by several years. Olfactory impairment is closely linked to the clinical symptoms and neuropathological biomarkers of AD, accompanied by significant structural and functional abnormalities in the brain. Olfactory behavior examination can subjectively evaluate the abilities of olfactory identification, threshold, and discrimination. Olfactory functional magnetic resonance imaging (fMRI) can provide a relatively objective assessment of olfactory capabilities, with the potential to become a promising tool for exploring the neural mechanisms of olfactory damage in AD. Here, we provide a timely review of recent literature on the characteristics, neuropathology, and examination of olfactory dysfunction in the AD continuum. We focus on the early changes in olfactory indicators detected by behavioral and fMRI assessments and discuss the potential of these techniques in MCI and preclinical AD. Despite the challenges and limitations of existing research, olfactory dysfunction has demonstrated its value in assessing neurodegenerative diseases and may serve as an early indicator of AD in the future.
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Affiliation(s)
- Dongming Liu
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Jiaming Lu
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Liangpeng Wei
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Mei Yao
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Huiquan Yang
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Pin Lv
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Haoyao Wang
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Yajing Zhu
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
| | - Zhengyang Zhu
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
| | - Xin Zhang
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Jiu Chen
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Qing X. Yang
- Department of Radiology, Center for NMR Research, Penn State University College of Medicine, Hershey, PA, United States
| | - Bing Zhang
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
- Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China
- Institute of Brain Science, Nanjing University, Nanjing, China
- Jiangsu Provincial Medical Key Discipline (Laboratory), Nanjing, China
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Wang Q, Yang Y, Wang K, Shen L, Chen Q. Fate of the second task in dual-task interference is associated with sensory system interactions with default-mode network. Cortex 2023; 166:154-171. [PMID: 37385005 DOI: 10.1016/j.cortex.2023.05.011] [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: 10/01/2022] [Revised: 03/01/2023] [Accepted: 05/23/2023] [Indexed: 07/01/2023]
Abstract
Psychological refractory period (PRP) effect refers to the delay in responding to the second of two tasks occurring in rapid succession. While all the major models of PRP highlight the importance of the frontoparietal control network (FPCN) in prioritizing the neural processing of the first task, the fate of the second task remains poorly understood. Here, we provide novel neural evidence on how the functional connectivity between sensory systems and the default-mode network (DMN) suspends the neural processing of the second task to ensure the efficient completion of the first task in dual-task situation. In a cross-modal PRP paradigm, a visual task could either precede or follow an auditory task. The DMN was generally deactivated during task performance and selectively coupled with the sensory system underlying the second task subjected to the PRP effect. Specifically, the DMN showed neural coupling with the auditory system when the auditory task came after the visual task, and with the visual system vice versa. More critically, the strength of the DMN-Sensory coupling correlated negatively with the size of the PRP effect: the stronger the coupling, the shorter the PRP. Therefore, rather than being detrimental to the dual-task performance, temporary suspension of the second task, via the DMN-Sensory coupling, surprisingly guaranteed the efficient completion of the first task by reducing the interference from the second task. Accordingly, the entry and processing of the second stimuli in the central executive system were speeded up as well.
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Affiliation(s)
- Qifei Wang
- Center for Studies of Psychological Application, South China Normal University, Guangzhou, China; School of Psychology, South China Normal University, Guangzhou, China
| | - Yuqian Yang
- Center for Studies of Psychological Application, South China Normal University, Guangzhou, China; Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Research Centre Jülich, Jülich, Germany
| | - Ke Wang
- Center for Studies of Psychological Application, South China Normal University, Guangzhou, China; Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Research Centre Jülich, Jülich, Germany
| | - Lu Shen
- Center for Studies of Psychological Application, South China Normal University, Guangzhou, China; School of Psychology, South China Normal University, Guangzhou, China.
| | - Qi Chen
- Center for Studies of Psychological Application, South China Normal University, Guangzhou, China; School of Psychology, South China Normal University, Guangzhou, China.
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Chung TWH, Zhang H, Wong FKC, Sridhar S, Lee TMC, Leung GKK, Chan KH, Lau KK, Tam AR, Ho DTY, Cheng VCC, Yuen KY, Hung IFN, Mak HKF. A Pilot Study of Short-Course Oral Vitamin A and Aerosolised Diffuser Olfactory Training for the Treatment of Smell Loss in Long COVID. Brain Sci 2023; 13:1014. [PMID: 37508945 PMCID: PMC10377650 DOI: 10.3390/brainsci13071014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/20/2023] [Accepted: 06/27/2023] [Indexed: 07/30/2023] Open
Abstract
Background: Olfactory dysfunction (OD) is a common neurosensory manifestation in long COVID. An effective and safe treatment against COVID-19-related OD is needed. Methods: This pilot trial recruited long COVID patients with persistent OD. Participants were randomly assigned to receive short-course (14 days) oral vitamin A (VitA; 25,000 IU per day) and aerosolised diffuser olfactory training (OT) thrice daily (combination), OT alone (standard care), or observation (control) for 4 weeks. The primary outcome was differences in olfactory function by butanol threshold tests (BTT) between baseline and end-of-treatment. Secondary outcomes included smell identification tests (SIT), structural MRI brain, and serial seed-based functional connectivity (FC) analyses in the olfactory cortical network by resting-state functional MRI (rs-fMRI). Results: A total of 24 participants were randomly assigned to receive either combination treatment (n = 10), standard care (n = 9), or control (n = 5). Median OD duration was 157 days (IQR 127-175). Mean baseline BTT score was 2.3 (SD 1.1). At end-of-treatment, mean BTT scores were significantly higher for the combination group than control (p < 0.001, MD = 4.4, 95% CI 1.7 to 7.2) and standard care (p = 0.009) groups. Interval SIT scores increased significantly (p = 0.009) in the combination group. rs-fMRI showed significantly higher FC in the combination group when compared to other groups. At end-of-treatment, positive correlations were found in the increased FC at left inferior frontal gyrus and clinically significant improvements in measured BTT (r = 0.858, p < 0.001) and SIT (r = 0.548, p = 0.042) scores for the combination group. Conclusions: Short-course oral VitA and aerosolised diffuser OT was effective as a combination treatment for persistent OD in long COVID.
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Affiliation(s)
- Tom Wai-Hin Chung
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Hui Zhang
- Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong, China
- Research Institute for Intelligent Wearable Systems, The Hong Kong Polytechnic University, Hong Kong, China
| | - Fergus Kai-Chuen Wong
- Department of Ear, Nose and Throat, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China
| | - Siddharth Sridhar
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China
| | - Tatia Mei-Chun Lee
- Department of Psychology, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, China
| | - Gilberto Ka-Kit Leung
- Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Koon-Ho Chan
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Kui-Kai Lau
- State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, China
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Anthony Raymond Tam
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Deborah Tip-Yin Ho
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Vincent Chi-Chung Cheng
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Kwok-Yung Yuen
- Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China
- The Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong, China
| | - Ivan Fan-Ngai Hung
- Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- The Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong, China
| | - Henry Ka-Fung Mak
- State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, China
- Department of Diagnostic Radiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Alzheimer's Disease Research Network, The University of Hong Kong, Hong Kong, China
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Wang J, Sun J, Gao L, Zhang D, Chen L, Wu T. Common and unique dysconnectivity profiles of dorsal and median raphe in Parkinson's disease. Hum Brain Mapp 2022; 44:1070-1078. [PMID: 36334274 PMCID: PMC9875924 DOI: 10.1002/hbm.26139] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 10/11/2022] [Accepted: 10/23/2022] [Indexed: 11/07/2022] Open
Abstract
The serotonergic (5-HT) system, which undergoes degeneration in Parkinson's disease (PD), is involved in the pathogenesis of motor and nonmotor symptoms. The dorsal raphe (DR) and median raphe (MR) nuclei are the main source of 5-HT neurons, however, brain connectivity changes in these two nuclei have not been delineated in PD. Here we used resting-state fMRI (rs-fMRI) to characterize functional connectivity profiles of DR and MR and further examine the associations between dysconnectivity of raphe nuclei and clinical phenotypes of PD. We found that DR and MR commonly hypo-connected with the sensorimotor, temporal, and occipital cortex, limbic system, left thalamus, putamen, and cerebellum in PD. DR had unique decreased connectivity with the bilateral prefrontal and cingulate cortices, while MR had lower connectivity with the pons. Moreover, reduced connectivity of DR correlated with depression, drowsiness, and anxiety, whereas dysconnectivity of MR correlated with depression, cognitive deficits, sleep disturbances, and pain. Our findings highlight the complex roles of raphe nuclei in motor and nonmotor symptoms, providing novel insights into the neurophysiological mechanisms underlying pathogenesis of PD.
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Affiliation(s)
- Junling Wang
- Center for Movement Disorders, Department of Neurology, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Junyan Sun
- Center for Movement Disorders, Department of Neurology, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Linlin Gao
- Department of General MedicineTianjin Union Medical CenterTianjinChina
| | - Dongling Zhang
- Center for Movement Disorders, Department of Neurology, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Lili Chen
- Center for Movement Disorders, Department of Neurology, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
| | - Tao Wu
- Center for Movement Disorders, Department of Neurology, Beijing Tiantan HospitalCapital Medical UniversityBeijingChina
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5
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Changes in the Intranetwork and Internetwork Connectivity of the Default Mode Network and Olfactory Network in Patients with COVID-19 and Olfactory Dysfunction. Brain Sci 2022; 12:brainsci12040511. [PMID: 35448042 PMCID: PMC9029634 DOI: 10.3390/brainsci12040511] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 04/13/2022] [Accepted: 04/14/2022] [Indexed: 12/21/2022] Open
Abstract
Olfactory dysfunction (OD) is a common symptom in coronavirus disease 2019 (COVID-19) patients. Moreover, many neurological manifestations have been reported in these patients, suggesting central nervous system involvement. The default mode network (DMN) is closely associated with olfactory processing. In this study, we investigated the internetwork and intranetwork connectivity of the DMN and the olfactory network (ON) in 13 healthy controls and 22 patients presenting with COVID-19-related OD using independent component analysis and region of interest functional magnetic resonance imaging (fMRI) analysis. There was a significant correlation between the butanol threshold test (BTT) and the intranetwork connectivity in ON. Meanwhile, the COVID-19 patients with OD showed significantly higher intranetwork connectivity in the DMN, as well as higher internetwork connectivity between ON and DMN. However, no significant difference was found between groups in the intranetwork connectivity within ON. We postulate that higher intranetwork functional connectivities compensate for the deficits in olfactory processing and general well-being in COVID-19 patients. Nevertheless, the compensation process in the ON may not be obvious at this stage. Our results suggest that resting-state fMRI is a potentially valuable tool to evaluate neurosensory dysfunction in COVID-19 patients.
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6
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Mijalkov M, Volpe G, Pereira JB. Directed Brain Connectivity Identifies Widespread Functional Network Abnormalities in Parkinson's Disease. Cereb Cortex 2022; 32:593-607. [PMID: 34331060 PMCID: PMC8805861 DOI: 10.1093/cercor/bhab237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 05/19/2021] [Accepted: 06/17/2021] [Indexed: 11/14/2022] Open
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder characterized by topological abnormalities in large-scale functional brain networks, which are commonly analyzed using undirected correlations in the activation signals between brain regions. This approach assumes simultaneous activation of brain regions, despite previous evidence showing that brain activation entails causality, with signals being typically generated in one region and then propagated to other ones. To address this limitation, here, we developed a new method to assess whole-brain directed functional connectivity in participants with PD and healthy controls using antisymmetric delayed correlations, which capture better this underlying causality. Our results show that whole-brain directed connectivity, computed on functional magnetic resonance imaging data, identifies widespread differences in the functional networks of PD participants compared with controls, in contrast to undirected methods. These differences are characterized by increased global efficiency, clustering, and transitivity combined with lower modularity. Moreover, directed connectivity patterns in the precuneus, thalamus, and cerebellum were associated with motor, executive, and memory deficits in PD participants. Altogether, these findings suggest that directional brain connectivity is more sensitive to functional network differences occurring in PD compared with standard methods, opening new opportunities for brain connectivity analysis and development of new markers to track PD progression.
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Affiliation(s)
- Mite Mijalkov
- Address correspondence to Mite Mijalkov and Joana B. Pereira, Department of Neurobiology, Care Sciences and Society, Division of Clinical Geriatrics, Karolinska Institutet, Neo 7th floor, Blickagången 16, 141 83 Huddinge, Sweden. (M.M.); (J.B.P.)
| | | | - Joana B Pereira
- Address correspondence to Mite Mijalkov and Joana B. Pereira, Department of Neurobiology, Care Sciences and Society, Division of Clinical Geriatrics, Karolinska Institutet, Neo 7th floor, Blickagången 16, 141 83 Huddinge, Sweden. (M.M.); (J.B.P.)
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7
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Jo HG, Wudarczyk O, Leclerc M, Regenbogen C, Lampert A, Rothermel M, Habel U. Effect of odor pleasantness on heat-induced pain: An fMRI study. Brain Imaging Behav 2021; 15:1300-1312. [PMID: 32770446 DOI: 10.1007/s11682-020-00328-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Odor modulates the experience of pain, but the neural basis of how the two sensory modalities, olfaction and pain, are linked in the central nervous system is far from clear. In this study, we investigated the mechanisms by which the brain modulates the pain experience under concurrent odorant stimulation. We conducted an fMRI study using a 2 × 3 factorial design, in which one of two temperatures (warm, hot) and one of three types of odors (pleasant, unpleasant, no odor) were presented simultaneously. "Hot" temperatures were individually determined as those perceived as painful (mean temperature = 46.9 °C). The non-painful "warm" temperature was set to 40 °C. Participants rated hot compared to warm stimuli as more intense and unpleasant, especially in the presence of an unpleasant odor. Parametric modeling on the intensity ratings activated the pain network, covering brain regions activated by the hot stimuli. The presence of an odor, irrespective of its valence, activated the amygdalae. In addition, the amygdalae showed stimulus-dependent functional couplings with the right supramarginal gyrus and with the left superior frontal gyrus. The coupling between the right amygdala and the left superior frontal gyrus was related to the intensity and unpleasantness ratings of the pain experience. Our results suggest that these functional connections may reflect the integrating process of the two sensory modalities, enabling olfactory influence on the pain experience.
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Affiliation(s)
- Han-Gue Jo
- Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH Aachen University, Aachen, Germany. .,JARA-Institute Brain Structure Function Relationship (INM-10), Research Center Jülich and RWTH Aachen University, Jülich, Germany. .,School of Computer, Information and Communication Engineering, Kunsan National University, Gunsan, South Korea.
| | - Olga Wudarczyk
- Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH Aachen University, Aachen, Germany.,Department of Psychology, Humboldt-Universität zu Berlin, Berlin, Germany.,Cluster of Excellence Science of Intelligence, Technische Universität Berlin and Humboldt Universität zu Berlin, 10587, Berlin, Germany
| | - Marcel Leclerc
- Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH Aachen University, Aachen, Germany
| | - Christina Regenbogen
- Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH Aachen University, Aachen, Germany.,JARA-Institute Brain Structure Function Relationship (INM-10), Research Center Jülich and RWTH Aachen University, Jülich, Germany.,Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Angelika Lampert
- Institute of Physiology, Medical Faculty, RWTH Aachen University, Aachen, Germany
| | - Markus Rothermel
- Department of Chemosensation, AG Neuromodulation, Institute for Biology II, RWTH Aachen University, Aachen, Germany
| | - Ute Habel
- Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH Aachen University, Aachen, Germany.,JARA-Institute Brain Structure Function Relationship (INM-10), Research Center Jülich and RWTH Aachen University, Jülich, Germany
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8
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Ahnaou A, Drinkenburg WHIM. Sleep, neuronal hyperexcitability, inflammation and neurodegeneration: Does early chronic short sleep trigger and is it the key to overcoming Alzheimer's disease? Neurosci Biobehav Rev 2021; 129:157-179. [PMID: 34214513 DOI: 10.1016/j.neubiorev.2021.06.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 05/13/2021] [Accepted: 06/25/2021] [Indexed: 01/13/2023]
Abstract
Evidence links neuroinflammation to Alzheimer's disease (AD); however, its exact contribution to the onset and progression of the disease is poorly understood. Symptoms of AD can be seen as the tip of an iceberg, consisting of a neuropathological build-up in the brain of extracellular amyloid-β (Aβ) plaques and intraneuronal hyperphosphorylated aggregates of Tau (pTau), which are thought to stem from an imbalance between its production and clearance resulting in loss of synaptic health and dysfunctional cortical connectivity. The glymphatic drainage system, which is particularly active during sleep, plays a key role in the clearance of proteinopathies. Poor sleep can cause hyperexcitability and promote Aβ and tau pathology leading to systemic inflammation. The early neuronal hyperexcitability of γ-aminobutyric acid (GABA)-ergic inhibitory interneurons and impaired inhibitory control of cortical pyramidal neurons lie at the crossroads of excitatory/inhibitory imbalance and inflammation. We outline, with a prospective framework, a possible vicious spiral linking early chronic short sleep, neuronal hyperexcitability, inflammation and neurodegeneration. Understanding the early predictors of AD, through an integrative approach, may hold promise for reducing attrition in the late stages of neuroprotective drug development.
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Affiliation(s)
- A Ahnaou
- Dept. of Neuroscience Discovery, Janssen Research & Development, A Division of Janssen Pharmaceutica NV, Turnhoutseweg 30, Beerse, B-2340, Belgium.
| | - W H I M Drinkenburg
- Dept. of Neuroscience Discovery, Janssen Research & Development, A Division of Janssen Pharmaceutica NV, Turnhoutseweg 30, Beerse, B-2340, Belgium
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Pain Perception, Brain Connectivity, and Neurochemistry in Healthy, Capsaicin-Sensitive Subjects. Neural Plast 2020; 2020:9125913. [PMID: 33178262 PMCID: PMC7644335 DOI: 10.1155/2020/9125913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 09/29/2020] [Accepted: 10/16/2020] [Indexed: 11/17/2022] Open
Abstract
Most of the occupational exposure limits (OELs) are based on local irritants. However, exposure to much lower concentrations of irritant substances can also lead to health complaints from workers. Exposure to irritants is often accompanied by strong unpleasant odors, and strong odors might have distracting effects and hence pose a safety risk. The findings obtained in human exposure studies with chemically sensitive, stressed, or anxious persons suggest that their ability to direct attention away from the odorous exposure and to focus on a cognitive task is reduced. In addition, after repeated odor exposure, these persons show signs of sensitization, i.e., difficulties in ignoring or getting used to the exposure. The question arises as to whether certain health conditions are accompanied by a change in sensitivity to odors and irritants, so that these persons are potentially more distracted by odors and irritants and therefore more challenged in working memory tasks than nonsusceptible persons. In our study, susceptible persons with sensory airway hyperreactivity ("capsaicin-sensitive") respond more strongly to mechanical skin stimuli than controls and show altered network connectivity. Capsaicin-sensitive subjects have a lower pain threshold and thus are more sensitive to mechanical skin stimuli. The intrinsic functional connectivity of their saliency network is higher, and the lower the GABAergic tone of the thalamus, the higher their pain sensitivity to mechanical stimuli. It seems that the increased communication between resting-state networks promotes a stronger perception of the sensory input signal. The results can be used to inform about actual risks (i.e., attention diversion and increased risk of accidents) and "pseudo" risks such as odor perception without a negative impact on one's well-being. This way, uncertainties that still prevail in the health assessment of odorous and sensory irritating chemicals could be reduced.
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10
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Functional Connectome Analyses Reveal the Human Olfactory Network Organization. eNeuro 2020; 7:ENEURO.0551-19.2020. [PMID: 32471848 PMCID: PMC7418535 DOI: 10.1523/eneuro.0551-19.2020] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Revised: 05/18/2020] [Accepted: 05/19/2020] [Indexed: 01/24/2023] Open
Abstract
The olfactory system is uniquely heterogeneous, performing multifaceted functions (beyond basic sensory processing) across diverse, widely distributed neural substrates. While knowledge of human olfaction continues to grow, it remains unclear how the olfactory network is organized to serve this unique set of functions. The olfactory system is uniquely heterogeneous, performing multifaceted functions (beyond basic sensory processing) across diverse, widely distributed neural substrates. While knowledge of human olfaction continues to grow, it remains unclear how the olfactory network is organized to serve this unique set of functions. Leveraging a large and high-quality resting-state functional magnetic resonance imaging (rs-fMRI) dataset of nearly 900 participants from the Human Connectome Project (HCP), we identified a human olfactory network encompassing cortical and subcortical regions across the temporal and frontal lobes. Highlighting its reliability and generalizability, the connectivity matrix of this olfactory network mapped closely onto that extracted from an independent rs-fMRI dataset. Graph theoretical analysis further explicated the organizational principles of the network. The olfactory network exhibits a modular composition of three (i.e., the sensory, limbic, and frontal) subnetworks and demonstrates strong small-world properties, high in both global integration and local segregation (i.e., circuit specialization). This network organization thus ensures the segregation of local circuits, which are nonetheless integrated via connecting hubs [i.e., amygdala (AMY) and anterior insula (INSa)], thereby enabling the specialized, yet integrative, functions of olfaction. In particular, the degree of local segregation positively predicted olfactory discrimination performance in the independent sample, which we infer as a functional advantage of the network organization. In sum, an olfactory functional network has been identified through the large HCP dataset, affording a representative template of the human olfactory functional neuroanatomy. Importantly, the topological analysis of the olfactory network provides network-level insights into the remarkable functional specialization and spatial segregation of the olfactory system.
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Lu J, Testa N, Jordan R, Elyan R, Kanekar S, Wang J, Eslinger P, Yang QX, Zhang B, Karunanayaka PR. Functional Connectivity between the Resting-State Olfactory Network and the Hippocampus in Alzheimer's Disease. Brain Sci 2019; 9:brainsci9120338. [PMID: 31775369 PMCID: PMC6955985 DOI: 10.3390/brainsci9120338] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 11/15/2019] [Accepted: 11/18/2019] [Indexed: 01/03/2023] Open
Abstract
Olfactory impairment is associated with prodromal Alzheimer's disease (AD) and is a risk factor for the development of dementia. AD pathology is known to disrupt brain regions instrumental in olfactory information processing, such as the primary olfactory cortex (POC), the hippocampus, and other temporal lobe structures. This selective vulnerability suggests that the functional connectivity (FC) between the olfactory network (ON), consisting of the POC, insula and orbital frontal cortex (OFC) (Tobia et al., 2016), and the hippocampus may be impaired in early stage AD. Yet, the development trajectory of this potential FC impairment remains unclear. Here, we used resting-state functional magnetic resonance imaging (rs-fMRI) data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to investigate FC changes between the ON and hippocampus in four groups: aged-matched cognitively normal (CN), early mild cognitive impairment (EMCI), late mild cognitive impairment (LMCI), and AD. FC was calculated using low frequency fMRI signal fluctuations in the ON and hippocampus (Tobia et al., 2016). We found that the FC between the ON and the right hippocampus became progressively disrupted across disease states, with significant differences between EMCI and LMCI groups. Additionally, there were no significant differences in gray matter hippocampal volumes between EMCI and LMCI groups. Lastly, the FC between the ON and hippocampus was significantly correlated with neuropsychological test scores, suggesting that it is related to cognition in a meaningful way. These findings provide the first in vivo evidence for the involvement of FC between the ON and hippocampus in AD pathology. Results suggest that functional connectivity (FC) between the olfactory network (ON) and hippocampus may be a sensitive marker for Alzheimer's disease (AD) progression, preceding gray matter volume loss.
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Affiliation(s)
- Jiaming Lu
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
- Medical School of Nanjing University, Nanjing 210008, China;
| | - Nicole Testa
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
| | - Rebecca Jordan
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
| | - Rommy Elyan
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
| | - Sangam Kanekar
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
| | - Jianli Wang
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
| | - Paul Eslinger
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
- Department of Neurology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Qing X. Yang
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
- Department of Neurosurgery, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Bing Zhang
- Medical School of Nanjing University, Nanjing 210008, China;
| | - Prasanna R. Karunanayaka
- Department of Radiology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; (J.L.); (N.T.); (R.J.); (R.E.); (P.E.); (Q.X.Y.)
- Department of Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
- Department of Public Health Sciences, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
- Correspondence: ; Tel.: +1-717-531-6069; Fax: +1-717-531-8486
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Georgiopoulos C, Witt ST, Haller S, Dizdar N, Zachrisson H, Engström M, Larsson EM. A study of neural activity and functional connectivity within the olfactory brain network in Parkinson's disease. NEUROIMAGE-CLINICAL 2019; 23:101946. [PMID: 31491835 PMCID: PMC6661283 DOI: 10.1016/j.nicl.2019.101946] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 06/23/2019] [Accepted: 07/17/2019] [Indexed: 01/16/2023]
Abstract
Olfactory dysfunction is an early manifestation of Parkinson's disease (PD). The present study aimed to illustrate potential differences between PD patients and healthy controls in terms of neural activity and functional connectivity within the olfactory brain network. Twenty PD patients and twenty healthy controls were examined with olfactory fMRI and resting-state fMRI. Data analysis of olfactory fMRI included data-driven tensorial independent component (ICA) and task-driven general linear model (GLM) analyses. Data analysis of resting-state fMRI included probabilistic ICA based on temporal concatenation and functional connectivity analysis within the olfactory network. ICA of olfactory fMRI identified an olfactory network consisting of the posterior piriform cortex, insula, right orbitofrontal cortex and thalamus. Recruitment of this network was less significant for PD patients. GLM analysis revealed significantly lower activity in the insula bilaterally and the right orbitofrontal cortex in PD compared to healthy controls but no significant differences in the olfactory cortex itself. Analysis of resting-state fMRI did not reveal any differences in the functional connectivity within the olfactory, default mode, salience or central executive networks between the two groups. In conclusion, olfactory dysfunction in PD is associated with less significant recruitment of the olfactory brain network. ICA could demonstrate differences in both the olfactory cortex and its main projections, compared to GLM that revealed differences only on the latter. Resting-state fMRI did not reveal any significant differences in functional connectivity within the olfactory, default mode, salience and central executive networks in this cohort. Less significant recruitment of the olfactory brain network was found in Parkinson's disease. Independent component analysis reveals differences in both olfactory cortex and its projections. Differences in functional connectivity within the olfactory network were not significant.
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Affiliation(s)
- Charalampos Georgiopoulos
- Department of Radiology and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
| | - Suzanne T Witt
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Sven Haller
- Centre Imagerie Rive Droite SA, Geneva, Switzerland; Department of Surgical Sciences/Radiology, Uppsala University, Uppsala, Sweden
| | - Nil Dizdar
- Department of Neurology and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Helene Zachrisson
- Department of Clinical Physiology and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
| | - Maria Engström
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden; Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
| | - Elna-Marie Larsson
- Department of Surgical Sciences/Radiology, Uppsala University, Uppsala, Sweden
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Lu J, Yang QX, Zhang H, Eslinger PJ, Zhang X, Wu S, Zhang B, Zhu B, Karunanayaka PR. Disruptions of the olfactory and default mode networks in Alzheimer's disease. Brain Behav 2019; 9:e01296. [PMID: 31165582 PMCID: PMC6625464 DOI: 10.1002/brb3.1296] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 03/28/2019] [Accepted: 04/03/2019] [Indexed: 12/13/2022] Open
Abstract
INTRODUCTION Olfactory deficits are prevalent in early Alzheimer's disease (AD) and are predictive of progressive memory loss and dementia. However, direct neural evidence to relate AD neurodegeneration to deficits in olfaction and memory is limited. METHODS We combined the University of Pennsylvania Smell Identification Test (UPSIT) with olfactory functional magnetic resonance imaging (fMRI) to investigate links between neurodegeneration, the olfactory network (ON) and the default mode network (DMN) in AD. RESULTS Behaviorally, olfactory and memory scores showed a strong positive correlation in the study cohorts. During olfactory fMRI, the ON showed reduced task-related activation and the DMN showed reduced task-related suppression in mild cognitive impairment (MCI) and AD subjects compared to age-matched cognitively normal subjects. CONCLUSIONS The results provide in vivo evidence for selective vulnerability of ON and DMN in AD and significantly improves the viable clinical applications of olfactory testing. A network-based approach, focusing on network integrity rather than focal pathology, seems beneficial to olfactory prediction of dementia in AD.
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Affiliation(s)
- Jiaming Lu
- Department of RadiologyThe Pennsylvania State University College of MedicineHersheyPennsylvania
- Drum Tower HospitalMedical School of Nanjing UniversityNanjingChina
| | - Qing X. Yang
- Department of RadiologyThe Pennsylvania State University College of MedicineHersheyPennsylvania
- Department of NeurosurgeryThe Pennsylvania State University College of MedicineHersheyPennsylvania
| | - Han Zhang
- Department of Radiology and Biomedical Research Imaging Center (BRIC)University of North Carolina at Chapel HillChapel HillNC
| | - Paul J. Eslinger
- Department of RadiologyThe Pennsylvania State University College of MedicineHersheyPennsylvania
- Department of NeurologyThe Pennsylvania State University College of MedicineHersheyPennsylvania
| | - Xin Zhang
- Drum Tower HospitalMedical School of Nanjing UniversityNanjingChina
| | - Sichu Wu
- Drum Tower HospitalMedical School of Nanjing UniversityNanjingChina
| | - Bing Zhang
- Drum Tower HospitalMedical School of Nanjing UniversityNanjingChina
| | - Bin Zhu
- Drum Tower HospitalMedical School of Nanjing UniversityNanjingChina
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Hummel T, Fark T, Baum D, Warr J, Hummel CB, Schriever VA. The Rewarding Effect of Pictures with Positive Emotional Connotation upon Perception and Processing of Pleasant Odors-An FMRI Study. Front Neuroanat 2017; 11:19. [PMID: 28377697 PMCID: PMC5359254 DOI: 10.3389/fnana.2017.00019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 02/28/2017] [Indexed: 01/05/2023] Open
Abstract
This fMRI study was designed to investigate the effect of cross-modal conditioning in 28 female volunteers. Subjects underwent initial fMRI block design scanning during which three pleasant olfactory stimuli were presented and had to be rated with respect to intensity and pleasantness. This was followed by an odor identification task spread out over 3 days: the experimental group was rewarded for successful trials (correct odor identification) with emotionally salient photos, whilst the control group only received randomly displayed, emotionally neutral, pictures. In the final scanning session, the odors were again presented, and subjects rated pleasantness and intensity. Both pleasantness ratings and fMRI data showed effects of the rewarding procedure. Activation in nucleus accumbens and the orbitofrontal cortex confirmed the hypothesis that learnt association of odors with visual stimuli of emotionally positive valence not only increases pleasantness of the olfactory stimuli but is also reflected in the activation of brain structures relevant for hedonic and reward processing. To our knowledge, this is the first paper to report successful cross-modal conditioning of olfactory stimuli with visual clues.
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Affiliation(s)
- Thomas Hummel
- Smell and Taste Clinic, Department of Otorhinolaryngology, Technische Universität Dresden Dresden, Germany
| | - Therese Fark
- Smell and Taste Clinic, Department of Otorhinolaryngology, Technische Universität Dresden Dresden, Germany
| | - Daniel Baum
- Smell and Taste Clinic, Department of Otorhinolaryngology, Technische Universität Dresden Dresden, Germany
| | - Jonathan Warr
- Smell and Taste Clinic, Department of Otorhinolaryngology, Technische Universität Dresden Dresden, Germany
| | - Cornelia B Hummel
- Smell and Taste Clinic, Department of Otorhinolaryngology, Technische Universität Dresden Dresden, Germany
| | - Valentin A Schriever
- Smell and Taste Clinic, Department of Otorhinolaryngology, Technische Universität Dresden Dresden, Germany
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