Brain Activities Related to Legibility of Text, Studied by Means of Near Infrared Spectroscopy

Using NIRS, we investigated brain activity in subjects searching for target characters in given text. Visual stimuli consisted of two different contrasts: positive and negative. Both stimuli were displayed for 30 sec on a cathode-ray tube (CRT: 21 inches). The subjects were instructed to watch a visual display on the CRT. This display included text without meaning. When target characters were detected, subjects were instructed to perform three tasks: (1) count the number of target characters by visual observation, (2) tap a button with the thumb and fingers of their left hand carefully and as fast as possible and (3) operate a mobile phone.