Trail making test (TMT) was developed as a neuropsychological test evaluating frontal lobe function. However, the contribution of frontal lobe in results of TMT is still controversial because studies in patients with brain injuries suggest the role of basal ganglia rather than frontal lobe in results of TMT.

To examine the contribution of frontal lobe in the results of TMT, we measured blood flow in frontal cortex during performance of computer version TMT-A and TMT-B.

Sixteen healthy student volunteers (8 male, 25.9±5.3 year old; 8 female, 22.0±2.9 year old) was used in the study. Seven laser beam probes and 8 sensor probes were put on frontal lobe, and absorbance of 695 nm and 830 nm infrared beams were measured at 10Hz by optic topography (ETG 4000, Hitachi, Medical Corporation, Tokyo, Japan).

Concentration of deoxyhemoglobin was decreased while concentration of oxyhemoglobin was increased in the prefrontal cortex during the performance of TMT-A and TMT-B.

The results suggest that blood flow increases in the prefrontal cortex during the performance of TMT, and possible involvement of this brain region in the performance of TMT.