Impaired Parahippocampus Connectivity in Mild Cognitive Impairment and Alzheimer’s Disease

Article type: Research Article

Authors: Liu, Jieqiong^{a; b} | Zhang, Xinqing^{a; *} | Yu, Chunshui^{c; d} | Duan, Yunyun^c | Zhuo, Junjie^{e; f} | Cui, Yue^{e; g} | Liu, Bing^{e; g} | Li, Kuncheng^c | Jiang, Tianzi^{e; f; g} | Liu, Yong^{e; g; *}

Affiliations: [a] Department of Neurology, Xuanwu Hospital of Capital Medical University, Beijing, China | [b] Department of Neurology, Cangzhou Central Hospital, Hebei Medical University, Cangzhou, China | [c] Department of Radiology, Xuanwu Hospital of Capital Medical University, Beijing, China | [d] Department of Radiology, Tianjin Medical University General Hospital, Tianjin, China | [e] Brainnetome Center, Institute of Automation, the Chinese Academy of Sciences, Beijing, China | [f] Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu, China | [g] National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, Beijing, China

Correspondence: [*] Correspondence to: Prof. Xinqing Zhang, Department of Neurology, Xuanwu Hospital of Capital Medical University, Beijing, 100053, China. Tel.: +86 10 8319 8673; Fax: +86 10 8319 8150; E-mail: xinqingzhang@263.net

Correspondence: [*] Correspondence to: Dr. Yong Liu, Brainnetome Center, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China. Tel.: +86 10 8254 4768; Fax: +86 10 8254 4777; E-mail: yliu@nlpr.ia.ac.cn

Abstract: Background:The parahippocampal gyrus (PHG) is an important region of the limbic system that plays an important role in episodic memory. Elucidation of the PHG connectivity pattern will aid in the understanding of memory deficits in neurodegenerative diseases. Objective:To investigate if disease severity associated altered PHG connectivity in Alzheimer’s disease (AD) exists. Methods:We evaluated resting-state functional magnetic resonance imaging data from 18 patients with amnestic mild cognitive impairment (MCI), 35 patients with AD, and 21 controls. The PHG connectivity pattern was examined by calculating Pearson’s correlation coefficients between the bilateral PHG and whole brain. Group comparisons were performed after controlling for the effects of age and gender. The functional connectivity strength in each identified region was correlated with the MMSE score to evaluate the relationship between connectivity and cognitive ability. Results:Several brain regions of the default mode network showed reduced PHG connectivity in the AD patients, and PHG connectivity was associated with disease severity in the MCI and AD subjects. More importantly, correlation analyses showed that there were positive correlations between the connectivity strengths of the left PHG-PCC/Pcu and left PHG-left MTG and the Mini-Mental State Examination, indicating that with disease progression from MCI to severe AD, damage to the functional connectivity of the PHG becomes increasingly severe. Conclusions:These results indicate that disease severity is associated with altered PHG connectivity, contributing to knowledge about the reduction in cognitive ability and impaired brain activity that occur in AD/MCI. These early changes in the functional connectivity of the PHG might provide some potential clues for identification of imaging markers for the early detection of MCI and AD.

Keywords: Alzheimer’s disease, functional connectivity, mild cognitive impairment, parahippocampus

DOI: 10.3233/JAD-150727

Journal: Journal of Alzheimer's Disease, vol. 49, no. 4, pp. 1051-1064, 2016