Effect of Omitting Offset Work on Functional Near-Infrared Spectroscopy: Comparison Between Keyboard and Voice Response

When examining cerebral activity, it is important to decrease a subject’s fatigue with an appropriate task design that also maintains data quality. This study evaluated how well devices designed to reduce fatigue would affect functional near-infrared spectroscopy (fNIRS) data. A WOT-100 10-channel wearable fNIRS system was used to study the prefrontal areas of thirteen healthy volunteers. The stimulation task was a consistent incongruent Stroop test, but with two variations. First, the subjects’ answers could be delivered either by vocalization or keyboard output. Second was whether or not there was an offset such as simple finger movements or vocalization during control periods. Four sessions using both variations were performed. The relative changes of fNIRS data during the stimulation periods were used as a marker for cerebral activity. There was only a significant difference in two channels (Channel 3: p = 0.040, Channel 9: p = 0.022) when voice output was used. The result might have been due to voice output being generated from the temporal area, near the prefrontal area. We found that the omission of offset with keyboard output might be possible as there was only a small effect, but offset with voice output is necessary.