THE MEASUREMENT OF BRAIN ACTIVITY BY NEAR-INFRARED SPECTROSCOPY IN SUBJECTS WITH MILD COGNITIVE IMPAIRMENT

Abstract

The aim of this study was to probe the brain activity in subjects with mild cognitive impairment (MCI) while they performed various tests. Fifteen MCI subjects of 78.9±9.8 years of age, with a mean MMSE score of 27.3±1.4, and 17 control subjects of 72.3±7.3 years of age, with a mean MMSE score of 29.3±0.9, were investigated using NIRS. All of the subjects took three types of tests. 1) The Kana pick-up test (Kana are Japanese letters). The subjects were instructed to select 5 specified letters from randomly arranged Kana letters (Task 1); and old Japanese fairy tales written entirely in Kana letters (Task 2). The test consists of 10 s of rest followed by 60 s to perform Task 1, then 20 s of rest and 60 s to perform Task 2. Each of these tasks was repeated twice. 2) A modified Stroop test. The subjects were asked to name the color of ink (Task 1) and the color of Chinese letters (Task 2). The test consists of 10 s of rest followed by 30 s to perform each task; the test was repeated three times. 3) The phonological verbal fluency task. The subjects were instructed to generate words beginning with a specified letter. The test consists of 10 s of task followed by 5 s of rest; the test was repeated 10 times. We used a 16-probe, 46-channeled NIRS device (OMM 3000, Shimazu Corporation, Japan). The task achievement levels in the MCI subjects were lower than those of the control subjects in the following tasks: Kana pick-up Task 1 (P<0.01), Kana pick-up Task 2 (P<0.001), modified Stroop test Task 2 (P<0.05) by Cochran-cox analysis. With the exception of Kana pick-up Task 1, the oxyHb concentrations were significantly decreased in the MCI subjects in comparison to the controls in all of the tests. The results in this study indicate that the frontal brain function was impaired in the stage of “MCI due to Alzheimer’s disease”. The measurement of oxyHb using NIRS is useful in the diagnosis of MCI.