Alterations in the limbic/paralimbic cortices of Parkinson's disease patients with hyposmia under resting-state functional MRI by regional homogeneity and functional connectivity analysis.
BACKGROUND
Hyposmia is a cardinal early symptom of Parkinson's disease (PD), but the pathophysiological mechanisms underlying it remain unclear. Resting-state functional MRI (RS-fMRI) demonstrates spontaneous neuronal activity. We hypothesized that there would be alterations in the olfaction-related regions of the limbic/paralimbic cortices in PD patients with obvious hyposmia by RS-fMRI.


METHODS
We used the "Five Odors for Olfactory Detection Arrays" to test the threshold of olfactory detection (TOD) for 54 PD patients and 22 age-matched controls. Using the mean TOD of the control group, patients were subdivided into two groups: PD with obvious hyposmia (OH-PD, n = 38) and PD with none/less obvious hyposmia (NOH-PD, n = 16). The regional brain activity of all subjects was investigated using RS-fMRI, in combination with regional homogeneity (ReHo) and functional connectivity (FC) analysis.


RESULTS
There were different ReHo values in the limbic/paralimbic cortices between the OH-PD and NOH-PD groups. ReHo was significantly decreased in OH-PD patients in parts of the traditional olfactory regions (e.g. the amygdala, olfactory gyrus, orbital frontal cortex, parahippocampal gyrus and insula) and some non-traditional olfactory centers (e.g. the rectal gyrus and superior temporal pole), while increased in the left anterior/posterior cingulate cortex. FC analysis revealed decreased functional connectivity within the limbic/paralimbic cortices, especially in regions with reduced ReHo in the OH-PD group.


CONCLUSIONS
PD with hyposmia is related to altered functional activity not only in the traditional olfactory center, but also in some non-traditional olfactory regions of the limbic/paralimbic cortices.
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Meilan
M
Su
Department of Vascular Surgery, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Song
S
Wang
Department of Radiology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Weidong
W
Fang
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Yingcheng
Y
Zhu
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Rong
R
Li
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Ke
K
Sheng
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Dezhi
D
Zou
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Yu
Y
Han
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China.
Xuefeng
X
Wang
Department of Neurology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, China. Electronic address: chengoumei01@aliyun.com.
Oumei
O
Cheng
D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods; D005260:Female; D006179:Gyrus Cinguli / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008032:Limbic System / Q000378:metabolism / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009812:Odorants; D000857:Olfaction Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism*; D010300:Parkinson Disease / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism*; D012146:Rest / Q000502:physiology; D012903:Smell / Q000502:physiology
Functional MRI; Functional connectivity; Hyposmia; Parkinson's disease; Regional homogeneity