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P1‐295: Longitudinal functional MRI demonstrates loss of hippocampal activation associated with clinical decline in nondemented older subjects
Author(s) -
Sperling Reisa,
O'Brien Jacqueline,
O'Keefe Kelly,
DeLuca Amy,
LaViolette Peter,
Pihlajamaki Maija,
Johnson Keith,
Blacker Deborah,
Dickerson Bradford
Publication year - 2008
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.2008.05.885
Subject(s) - hippocampal formation , episodic memory , medicine , longitudinal study , neuroscience , hippocampus , audiology , cognitive decline , psychology , cardiology , cognition , dementia , pathology , disease
with a focus on the dorsolateral prefrontal cortex (DLPFC) as a region of interest because of its role in executive functions and working memory, and because of its frequent involvement in fMRI studies of cognitive tasks. Methods: Four patients with mild AD and eight healthy older adults were scanned on a 4-Tesla Varian-Oxford human imaging system. The subjects were instructed to remain relaxed while focusing their eyes on a central fixation for over 60 seconds. Functional images were acquired using two-shot spiral readout; 22 axial slices of 5.5 0.5mm. Data were processed using independent component analysis and artifacts attributed to physical and physiological sources were filtered. The time course of the representative resting state components (ICs) that were common across AD and healthy subjects were identified and analyzed applying GLM (p 0.001, uncorrected, extent 6). Signal changes, measured as the percentage difference between the highest and lowest of three consecutive fMRI data points during a scan were calculated. Results: The fMRI signals filtered for known imaging signal to noise ratio and physiological variations fluctuated during the resting phase. Three ICs were identified across subjects with each being characterized as a low frequency response ( 0.08Hz). Within the DFPLC, both the mean percentage change of the signal and the statistics in the contrast maps (i.e., for an IC) were greater in AD patients than in cognitively healthy older subjects. Conclusions: Regular patterns of fluctuations in fMRI indices of neural activity exist during rest and patients with mild AD demonstrated increased resting-state DLPFC activity. These resting state differences may reflect an early neurocompensatory response to AD.