Dissociation of regional activation in mild AD during visual encoding: a functional MRI study.
OBJECTIVE
The authors studied mild patients with AD with a visual learning paradigm to determine whether activations of medial temporal regions on fMRI differ in AD compared to nondemented individuals.


BACKGROUND
Changes in activation patterns of medial temporal lobe regions may serve as a biologic marker of altered brain function early in the course of AD.


METHODS
The authors studied eight healthy young subjects, eight late middle-age nondemented volunteers, and seven patients with mild AD. All subjects underwent fMRI scanning in which they viewed a set of geometric designs for 45 seconds. Changes in blood flow were analyzed by comparing the prestimulus fMRI signal with that present during the stimulus presentation.


RESULTS
Patients with AD, who had very poor recall of the geometric designs subsequently, showed increased blood flow (activation) during stimulus presentation only in a visual association area. Both the young and older nondemented subjects, all of whom had good recall of the designs, showed activations during stimulus presentation of the right entorhinal cortex, right supramarginal gyrus, right prefrontal regions, and left anterior-inferior temporal lobe. The younger and older nondemented subjects did not differ in fMRI activation patterns.


CONCLUSIONS
Failure of activation in AD of either temporal lobe or prefrontal regions is consistent with established clinical-pathologic correlations in AD. fMRI may be useful in confirming a memory disorder diagnosis and also may be useful in detecting individuals with incipient dysfunction in learning as a result of disorders such as AD.
Kato
T
T
Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, USA.
Knopman
D
D
Liu
H
H
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology*; D000704:Analysis of Variance; D004213:Dissociative Disorders / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods; D013702:Temporal Lobe / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology