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IC‐P2‐147: Covert orienting of visual attention task in asymptomatic individuals at increased risk for Alzheimer's disease
Author(s) -
Verduzco Guillermo,
Cristinzio Catherine,
Beauregard C.E.,
Bassett Susan Spear
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.2008.05.2601
Subject(s) - posterior cingulate , psychology , grey matter , covert , voxel , audiology , neuroscience , functional magnetic resonance imaging , cognitive psychology , medicine , magnetic resonance imaging , white matter , linguistics , philosophy , radiology
Background: Recent Voxel Based Morphometry (VBM) studies of individuals with Mild Cognitive Impairment (MCI) who have converted to Alzheimer’s disease (AD) have reported grey matter loss in the posterior cingulate as a predictor of conversion. This region is involved in memory and attention processing and appears to be the sub-region of the cingulate most affected in familial AD cases. Thus the posterior cingulate is a logical target of investigation as a site of early brain change in asymptomatic individuals at genetic risk for AD. Methods: Fifty-eight right-handed individuals at risk for familial AD and 56 right-handed matched controls underwent an fMRI paradigm based on the Covert Orienting of Visual Attention Task (COVAT) used in other studies. The groups did not differ in age, gender ratio, or years of education. This task has been shown to generate significant activation loci within the posterior cingulate gyrus. We examined fMRI activation due to indirect cueing of visual attention. This activation corresponds to the anticipatory advantage gained by the covert orientation of the subject’s visual attention. Functional data were processed and analyzed using SPM99, and anatomical labels were determined using MNI2Tal and Talairach Daemon software. Results: A one sample t-test revealed several statistically significant points of activation (P 0.001, cluster threshold 25 voxels) in the control group during the anticipatory advantage condition. The activation loci of greatest interest in the controls were in the bilateral posterior cingulate gyrii (BA 31). The at-risk group failed to show any areas of significant activation at the same threshold levels. A two sample t-test did not reach significance. Conclusions: As expected, the COVAT task produced posterior cingulate activation in the control subjects. The absence of this effect in the at-risk group suggests the lack of involvement of the posterior cingulate in their visual orientation. Longitudinal follow-up is needed to determine whether this lack of activation is ultimately related to development of AD.