Characteristics of Odor Identification and Hedonics and Their Association with Piriform Cortex-Based Resting-State Functional Connectivity in Amnestic Mild Cognitive Impairment

Article type: Research Article

Authors: Tu, Lihui^{a; b; c} | Wang, Zhijiang^{a; b} | Lv, Xiaozhen^{a; b} | Xie, Teng^{a; b} | Fan, Zili^{a; b; c} | Zhang, Ming^{a; b; d} | Wang, Huali^{a; b; *} | Yu, Xin^{a; b; *}

Affiliations: [a] Dementia Care and Research Center, Clinical Research Division, Peking University Institute of Mental Health, Sixth Hospital, Haidian District, Beijing, China | [b] Beijing Dementia Key Lab, National Clinical Research Center for Mental Disorders, Key Laboratory of Mental Health, Ministry of Health, Peking University, Beijing, China | [c] The National Clinical Research Center for Mental Disorders & Beijing Key Laboratory of Mental Disorders, Beijing Anding Hospital, Capital Medical University, Beijing, China | [d] Department of Psychiatry, the Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China

Correspondence: [*] Correspondence to: Dr. Huali Wang, Dementia Care and Research Center, Peking University Institute of Mental Health, No.51 Huayuanbei Road, Beijing 100191, China. Tel.: +86 10 82801983; Fax: +86 10 62026310; E-mail: [email protected] and Dr. Xin Yu, Beijing Dementia Key Lab, Peking University Institute of Mental Health, No.51 Huayuanbei Road, Beijing 100191, China. Tel.: +86 10 82801999; Fax: +86 10 62026310; E-mail: [email protected].

Abstract: Background:Olfactory identification dysfunction (OID) might be an early sign of amnestic mild cognitive impairment (aMCI). However, odor hedonics, the ability to perceive odor pleasantness, is neglected. Also, the neural substrate of OID remains unclear. Objective:To explore the characteristics of odor identification and hedonics in aMCI and examine the potential neural correlates of OID by analyzing olfactory functional connectivity (FC) patterns in MCI. Methods:Forty-five controls and 83 aMCI patients were examined. The Chinese smell identification test was used to assess olfaction. Global cognition, memory, and social cognition were assessed. Resting-state functional networks associated with olfactory cortex seeds were compared between the cognitively normal (CN) and aMCI groups, as well as between aMCI subgroups by the degree of OID. Results:Compared to controls, aMCI patients had a significant deficit in olfactory identification, mainly reflected in the identification of pleasant and neutral odors. aMCI patients also rated pleasant and neutral odors much lower than controls. A positive correlation between olfaction and social cognition was found in aMCI. The seed-based FC analysis found that aMCI patients had higher FC between the right orbitofrontal cortex and right frontal lobe/middle frontal gyrus than controls. Subgroup analysis showed that, compared to aMCI without OID, aMCI with severe OID had abnormal FC in the bilateral piriform region. Conclusion:Our results suggest that OID in aMCI primarily refers to the identification of pleasant and neutral odors. The FC alterations in bilateral orbitofrontal cortex and piriform cortices might contribute to the impairment in odor identification.

Keywords: Alzheimer’s disease, mild cognitive impairment, odor hedonics, olfactory identification, resting-state functional magnetic resonance imaging, social cognition

DOI: 10.3233/JAD-221163

Journal: Journal of Alzheimer's Disease, vol. 94, no. 1, pp. 247-258, 2023