Abnormal functional connectivity of hippocampus during episodic memory retrieval processing network in amnestic mild cognitive impairment.
BACKGROUND
Functional connectivity magnetic resonance imaging technique has revealed the importance of distributed network structures in higher cognitive processes in the human brain. The hippocampus has a key role in a distributed network supporting memory encoding and retrieval. Hippocampal dysfunction is a recurrent finding in memory disorders of aging such as amnestic mild cognitive impairment (aMCI) in which learning- and memory-related cognitive abilities are the predominant impairment. The functional connectivity method provides a novel approach in our attempts to better understand the changes occurring in this structure in aMCI patients.


METHODS
Functional connectivity analysis was used to examine episodic memory retrieval networks in vivo in twenty 28 aMCI patients and 23 well-matched control subjects, specifically between the hippocampal structures and other brain regions.


RESULTS
Compared with control subjects, aMCI patients showed significantly lower hippocampus functional connectivity in a network involving prefrontal lobe, temporal lobe, parietal lobe, and cerebellum, and higher functional connectivity to more diffuse areas of the brain than normal aging control subjects. In addition, those regions associated with increased functional connectivity with the hippocampus demonstrated a significantly negative correlation to episodic memory performance.


CONCLUSIONS
aMCI patients displayed altered patterns of functional connectivity during memory retrieval. The degree of this disturbance appears to be related to level of impairment of processes involved in memory function. Because aMCI is a putative prodromal syndrome to Alzheimer's disease (AD), these early changes in functional connectivity involving the hippocampus may yield important new data to predict whether a patient will eventually develop AD.
Bai
Feng
F
School of Clinical Medicine, Southeast University, Affiliated ZhongDa Hospital of Southeast University, Nanjing, Jiangsu 210009, China.
Zhang
Zhijun
Z
Watson
David R
DR
Yu
Hui
H
Shi
Yongmei
Y
Yuan
Yonggui
Y
Zang
Yufeng
Y
Zhu
Chaozhe
C
Qian
Yun
Y
D000368:Aged; D000647:Amnesia / Q000150:complications / Q000473:pathology*; D001931:Brain Mapping; D003072:Cognition Disorders / Q000150:complications / Q000473:pathology*; D005260:Female; D006624:Hippocampus / Q000098:blood supply / Q000503:physiopathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D009434:Neural Pathways / Q000098:blood supply / Q000503:physiopathology; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D011930:Reaction Time / Q000502:physiology; D018709:Statistics, Nonparametric
D010100:Oxygen