Premium
IC‐P‐140: Involvement of Central Olfactory System in AD and MCI
Author(s) -
Martinez Brittany,
Karunanayaka Prasanna,
Wang Jianli,
Cartisano Emma,
Vasavada Megha,
Eslinger Paul J.,
Yang Qing X.
Publication year - 2016
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2016.06.170
Subject(s) - odor , olfactory system , neuroscience , psychology , olfactory memory , olfaction , central nervous system , alzheimer's disease , olfactory bulb , disease , medicine , pathology
Background: Olfactory deficits are prominent early signs of Alzheimer’s disease. However, whether or not these deficits stem from pathology in the central or peripheral olfactory system remains unclear. The purpose of this study was, therefore, to further elucidate the source of disease-related olfactory deficits by combining olfactory fMRI with unified structural equation modeling (uSEM), a technique capable of revealing the causal relationships of the olfactory system. Methods: Alzheimer’s (AD, n1⁄416), Mild Cognitive Impairment (MCI 1⁄4 24) and older cognitively normal (CN, n1⁄437) subjects completed an olfactory fMRI paradigm that was specifically designed to evaluate the central olfactory system on a 3T MRI system (Figure 1). This paradigm included both odor and no-odor conditions, which were combined with a visual cue “Smell?”. The odor condition was designed to utilize both the peripheral and central olfactory systems, while the no-odor condition utilized only the central components. uSEM was then applied to these data to assess the olfactory network connectivity associated with AD. Results: The olfactory fMRI data demonstrates that the CN subjects had a greater activated volume of the primary olfactory cortex during both the odor and no-odor conditions than AD subjects (p < 0.05). Compared to AD subjects during the no-odor condition, the CN subjects displayed greater activation in the dlPFC, which is known to be involved in higher cognitive functions such as working memory (Figure 2). The uSEM analysis further revealed that MCI and AD network connectivity are changed considerably from that of CN, specifically between the primary olfactory cortex (POC), lateral prefrontal cortex (LPC) and the orbitofrontal cortex (OFC) (Figure 3). Conclusions:The functional activity and connectivity during odor processing in the central olfactory system are altered dramatically as revealed by fMRI and the uSEM analysis, indicating its involvement in AD functional pathology. Thus, olfactory fMRI can potentially be a non-subjective functional marker for early diagnosis and quantitative evaluation of AD.