Perfusion fMRI detects deficits in regional CBF during memory-encoding tasks in MCI subjects

Objective: To determine how memory-encoding tasks elicit functional perfusion change in subjects with amnestic mild cognitive impairment ( aMCI). Methods: Twelve subjects with aMCI and 14 age- matched cognitively normal ( CN) subjects were recruited for this study. Arterial spin-labeling perfusion MRI ( ASL- MRI) was employed to measure regional cerebral blood flow ( CBF) during both control and encoding task conditions. Results: Experimental results demonstrated that hypoperfusion occurred in the right precuneus and cuneus in the aMCI group, and not the CN group, during the control state. During the memory-task performance, the difference in these regional hypoperfusion areas extended to the posterior cingulate. These regional perfusion rates correlated with the Mini-Mental State Examination and the Rey Auditory Verbal Learning Test scores. In addition, a CBF percentage increase ( 22.7%) occurred in the right parahippocampus region during the memory-encoding task performance in the CN group, with approximately no change in the aMCI group. Conclusion: Subjects with amnestic mild cognitive impairment had significant regional cerebral hypoperfusion and lacked the dynamic capability to modulate their regional cerebral blood flow responses to the challenge of the functional tasks.