Verbal Learning in Alzheimer’s disease and Mild Cognitive Impairment: neuroanatomic correlates of acquisition and consolidation performances

The aim of this study was to examine correlations between impaired memory acquisition/consolidation and brain metabolism at rest in Alzheimer’s disease.
44 confirmed Alzheimer patients (AD), 16 patients with mild cognitive impairment (MCI) who converted to AD (MCI-C) (4-8 years of follow-up), 15 MCI patients who remained stable and 12 healthy elderly controls were administered the California Verbal Learning Task (CVLT) at entry. Acquisition and consolidation memory scores were calculated respectively as mean gained and total lost access across the 5 study-test trials (p = 0.05). Brain metabolism was measured by 18FDG-PET. Cognitive-metabolic correlations were performed with SPM8 (p<0.05 uncorrected).
Mean gained access was significantly lower in the AD group than in the control and MCI-S group and was significantly lower in the MCI-C group than in the control group. Mean gained access was significantly correlated to metabolism in the left precentral gyrus and IPS fondus in the control group, in the left and right inferior parietal lobules in the MCI-S group and in the left hippocampus in the AD group. Total lost access was greater in AD patients compared to control participants. No significant correlation between total lost access and brain metabolism was found.
The acquisition process is impaired in AD patients at a very early stage of the disease (MCI-C). This deficit is linked to metabolic changes in a frontoparieto-hippocampal learning network. In addition, consolidation process is specifically impaired in confirmed AD patients, while this deficit was not significantly correlated to brain metabolism in our participant groups.