Identification of three factors influencing trail making test performance using multichannel near-infrared spectroscopy.

Recent advances in medical care have facilitated the survival of patients with stroke or traffic-related injuries. However, such patients may suffer from higher brain dysfunction; i.e., an impaired ability to plan and perform behaviors based on prior knowledge. The Trail Making Test (TMT) is a cognitive task that is used to evaluate higher brain dysfunction caused by frontal lobe injury. TMT consists of two tasks; TMT-A involves connecting consecutive numbers, and TMT-B involves connecting numbers and letters alternately. In this study, using near-infrared spectroscopy (NIRS) and the achievement value (TMT score), we investigated the effects of three factors on TMT performance: knowledge of the TMT, the order of TMT-A and TMT-B performance, and gender. The subjects were 48 healthy adults, consisting of college graduates and undergraduates (age: 22.8 ± 2.5 years, education: 16.0 ± 1.2 years, 24 males and 24 females). We measured the changes in oxygenated hemoglobin (oxy-Hb) levels using NIRS, showing that the increase in oxy-Hb was higher in subjects who had no knowledge of the TMT than those who had prior knowledge. In both TMT-A and TMT-B, the subjects who performed their first task displayed higher oxy-Hb levels. Moreover, the oxy-Hb level in males was higher than that in females. In contrast, only the order of TMT performance showed noticeable effect on the TMT score. In the present study, using NIRS we have shown that either knowledge of the TMT, the order of the TMT, or gender affects TMT performance, providing invaluable information for interpreting TMT results.