Contrast effects of display colors on Hb concentration changes in the frontal lobe of elderly and young people

The combination display of the background color and font is one of the factors that affect psychological functioning. Many studies investigated the contrast effect on psychological well-being in connection with cognitive activity and task performance. These studies including our previous study, demonstrated the significant effects on brain activity and memory task, especially on elderly subjects. In this paper, we further discussed the contrast effects on the brain activity measured in the frontal lobe of young and elderly subjects. We measured hemoglobin (Hb) concentration changes by using near-infrared spectroscopy (NIRS) when the subjects performing the working memory task (reading span task) on three different display background colors (white, blue, green). Elderly subjects had a lower score on the task compared to younger subjects, which expressed a significant effect of aging, but no significant differences between background colors. On the other hand, the increment trend of the cognitive activity throughout the experiment showed task difficulty induced the blood flow in the brain. Between background colors, the brain activity of the young subject had a negative correlation on the contrast ratio where the low contrast ratio activated their brain activity the most. However, the elderly subject had the opposite results where the higher the contrast ratio, the more activation occurred in their brain. In conclusion, our finding is a key needed to keep activating the brain of elderly people where it tends to experience ability deterioration.