Monitoring of Brain Function by Near Infrared Spectroscopy (NIRS) for Prevention of Brain Diseases

Abstract

We developed a simple technique for objective assessment of mental stress levels by measuring hemoglobin concentration changes in the bilateral prefrontal cortex (PFC) at rest, employing two-channel near-infrared spectroscopy (NIRS). Each subject was instructed to think about nothing in particular NIRS measurements were taken and the left/right asymmetry of PFC activity at rest was evaluated by calculating the proposed Laterality Index at Rest (LIR). There was significant positive correlation between LIR and the State-Trait Anxiety Inventory (STAI) score. The present method allowed evaluation of mental stress level from NIRS measurements at rest. I. INTRODUCTION In order to prevent stress-induced diseases, we have developed a simple technique for objective assessment of mental stress levels, employing NIRS. II. MATERIALS AND METHODS A. Experimental settings The study population comprised 39 subjects (19 were 20-24 years old and 20 were 60-79 years old). We measured oxy- and deoxy-Hb concentration changes in the bilateral PFC with a two-channel NIRS. First, each subject completed the STAI questionnaire before NIRS measurements. Second, the subject was told that the preparation period (one min) would begin. Third, the subject was instructed to rest quietly for three minutes: rest period. This corresponds to the analysis period.