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Abstract:
Abstract: Goal: TO characterize the pattern of PET activation
during picture naming in Alzheimer's Disease subjects compared with
normal elderly controls. Methods: oxygen-15 water bolus PET studies
were carried out in 15 mild Alzheimer's Disease (AD) subjects and
15 elderly controls, during a baseline condition and during naming
of familiar (easy) and unfamiliar (hard) pictures of animals.
Results were analyzed in terms of subtraction scans as well as
regression maps of each subject's picture naming accuracy regressed
onto blood flow. Results: Normals were as accurate in naming hard
animal pictures (57% correct) as AD subjects were in naming easy
pictures (63% correct). Both regression maps and hard minus easy
picture subtraction scans produced activation of posterior left
temporal lobe in normals but not AD subjects. All naming conditions
produced activation of inferior temporo-occipital cortex
bilaterally, which was not increased for hard compared to easy
picture naming.This was equivalent in the two subject groups. When
picture naming accuracy was decreased, both AD and normal groups
showed activation in anterior cingulate and frontal lobe regions.
Conclusions:Inferior temporo-occipital activation is not influenced
by semantic difficulty of the pictures, and therefore represents
process- ing of the structural aspects of pictures. Posterior left
temporal lobe activation, presumably the neural correlate of
semantic processing, is not seen in AD, even for difficult
pictures.Task difficulty effects are seen in cingulate and frontal
regions.
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