BASELINE POSTERIOR CINGULATE CORTEX-MEDIAL TEMPORAL/HIPPOCAMPAL NETWORKS IN MCI PREDICTS THE EFFECT OF COGNITIVE TRAINING

Abstract

Mild cognitive impairment (MCI) is well known as a state between normal aging and Alzheimer's disease (AD). Cognitive training has been widely studied for its prevention effect in MCI patients. The results are controversial in different clinical trials. Cognitive training might work by modulating neural plasticity, and the threshold of modulation varies between individuals. It is important to find out prognostic neural markers for the effect of cognitive training before such intervention. We recruited thirty MCI patients and trained them for six months. Training covered memory, attention, language, visual spatial and executive function. Mini-mental state examination (MMSE) was done before and after training. Resting state functional MRI (Rs-fMRI) was also performed before training. MMSE of AD patients decrease 2 points per year according to epidemiological study. After six-month intervention, we grouped these patients by their MMSE difference between endpoint and baseline. Progressed group has 12 patients, which is defined by 1 points MMSE reduction. Effective group has 18 patients, which is defined by less than 1 points reduction of MMSE. Blood oxygenation level-dependent signals (BOLD) from fMRI were analyzed after pre-processing. We used seed-based functional connectivity (FC) for extracting default mode network (DMN) by seed in the posterior cingulate cortex (PCC). We also explored the connectivity between bilateral hippocampus and other voxels in the brain and compared the two groups with each other. Two groups were similar in their age, education level and baseline cognitive tests (MMSE, auditory verbal learning test, shape trail test, symbol digit substitution test, stroop color-word test and complex figure test). Baseline DMN of effective group showed increased connectivity between cortex peripheral to right lateral fissure and PCC. FC between bilateral hippocampus and PCC was also stronger in effective group than progressed group.