Table 1.

Summary of functional magnetic resonance imaging study findings during episodic memory encoding and retrieval

Cognitive task	Findings in Alzheimer's disease	Findings in MCI
Episodic memory encoding	↓activation in MTL	↓adaptive attenuation of hippocampus activation with repeated exposure
	↑activatio n in right DLPFC, left VLPFC, left OFC, superior temporal gyri, fusiform gyri, and left thalamus	↓ activation in MTL structures and in bilateral frontal regions in well-characterized amnestic MCI
	↓ activation cingulate, right mPFC, right insula, right superior parietal lobule, and left precuneus	Delayed BOLD response
		↑ MTL activation in early MCI patients who had comparable task performance with controls, extent of MTL activity positively correlated with successful encoding
		Greater MTL functional MRI activation at baseline predicted conversion to Alzheimer's disease
		↑ activation in posterior hippocampus and parahippocampal and fusiform regions, together with atrophy of more anterior MTL
Episodic memory retrieval	↓ activation in MTL	↑ activity in PCC
	↑ activation in right DLPFC and left VLPFC, left supramarginal, and left precuneus, and right thalamus	↓ activity in bilateral frontal regions and left hippocampus
	↓ activation in left claustrum/amygdala, and bilateral insula

Summary of functional MRI study findings during episodic memory encoding and retrieval in Alzheimer's disease and MCI patients compared with healthy controls based on recent meta-analysis by Schwindt and colleagues [21] and reviews by Ries and colleagues [22] and Dickerson and Sperling [23]. BOLD, blood oxygen level dependent; DLPFC, dorsolateral prefrontal cortex; MCI, mild cognitive impairment; mPFC, medial prefrontal cortex; MRI, magnetic resonance imaging; MTL, medial temporal lobe; OFC, orbitofrontal cortex; PCC, posterior cingulate cortex; VLPFC, ventrolateral prefrontal cortex.