IC-P1-037: Functional magnetic resonance imaging activation patterns in cognitively normal elderly, amnestic, and non-amnestic Mild Cognitive Impairment during a recognition memory task

Abstract

Investigators are increasingly focusing their attention on changes in extra-temporal circuitry in amnestic MCI (aMCI), with growing evidence for disruption in parietal and frontal functionality. The concept of MCI has recently evolved to include non-amnestic syndromes (naMCI) so very little is known about functional changes in these subjects. Our objective was to compare fMRI activation in cognitively normal elderly (CN), aMCI, and naMCI subjects. Twenty-nine CN, 19 aMCI, and 12 naMCI subjects completed a block-design recognition memory paradigm at 3.0T. Subjects were instructed to respond to color photographs they recognized from a previous encoding task completed earlier in the same scanning session. The threshold for significance was set at p < .001 (uncorrected) for within group analysis of fMRI activation using SPM2. CN subjects activated a network that included the medial and lateral frontal lobes, anterior cingulate, thalamus, posterior hippocampus, fusiform gyrus, posterior cingulate, and lateral temporal-parietal-occipital lobes in a bilaterally symmetric manner (figure). Amnestic MCI subjects activated the same regions (except the thalamus) but with less magnitude. Non-amnestic MCI subjects activated the same regions as CN and aMCI (except the thalamus and posterior cingulate) but with less magnitude still than either CN or aMCI. There were no areas in which the naMCI group showed increased activation compared to aMCI. There were also no areas in which the aMCI and naMCI groups had more activation than CN. The network activated by a recognition memory paradigm is largely similar among CN, aMCI, and naMCI. However, the strength of activation is ordered CN > aMCI > naMCI. We interpret the decreased activation observed in naMCI on what is nominally a “memory” task to represent non-memory components of the task in the domains of attentional and visuospatial function.