Calculation Ability In Small Vascular Mild Cognitive Impairment And Normal Aging: A Functional Magnetic Resonance Imaging Study

Objective To explore the difference of arithmetic calculation between the heathy olders and the patients with small vascular mild cognitive impairment(svMCI)with functional magnetic resonance imaging(fMRI).Methods 22 patients with small vascular mild cognitive impairment and 12 healthy olders were scanned by MRI when they performed complex calculation. The raw data of the fMRI were processed with the software SPM5. Numbers of activated voxels were used to calculate laterality index(LI),which was used for the evaluation of the laterality of functional areas in frontal lobe and parietal lobe.The reaction time and correct ratio were analyzed between svMCI group and control group. Results The behavior data showed that in number identifying task the correct rate in MCI was 95.97% and in control was 99.31% while the reaction time in MCI group was 800.5±182.0ms and in control group was 720.2±97.0ms,respectively. There were statistic differentia (P <0.05)between patient group and control group in the correct rate during number identifying task, but no statistic differentia in the reaction time.In complex substraction task,the correct rate in MCI group was 75.41% and in normal control group was 90.21% while the reaction time in MCI group was 1823.8±215.2ms and in control group was 1557.9±172.4ms,respectively. It had statistic differentia (P <0.05)between groups in the correct rate and reaction time in complex substraction task.Brain functional results showed that svMCI group and normal control group had many similar brain activation areas ,which suggested that many areas of brain participated in the subtraction calculation. Compared to the control group, the MCI group showed hypoactivity in bilateral parietal lobe (inferior parietal lobule mainly), bilateral middle frontal gyrus, bilateral hippocampus, parahippocampal gyrus, right posterior cingulate gyrus, bilateral middle temporal gyrus, left inferior temporal gyrus, bilateral occipital and bilateral cerebellar(P <0.005). In complex substraction, for both right handed groups, activation of functional areas of frontal and parietal lobe had the left laterality. In normol control group, the laterality index of parietal lobe was higher than that of frontal lobe,while in svMCI group it was on the contrary. Conclusion The patients with MCI has the deficit in calculation ability and some extend compensation is present. The study of the calculation fMRI can offer a powerful reference for the diagnosis of MCI.