fNIR spectroscopy as a measure of cognitive task load

Functional near infrared (fNIR) sensor measures hemodynamic changes in the cortex using a portable, safe, affordable and negligibly intrusive NIR based optical brain imaging system. We hypothesize that there is a positive correlation between blood oxygenation in the relevant areas of dorsolateral prefrontal cortex and cognitive effort defined as attention and working memory. In this paper, we present the employment of the fNIR sensor to assess the cognitive state of the user. The paper also introduces the experimental setup and analysis of the fNIR data acquired from the forehead during a video-game like task namely, "Warship Commander Task" (WCT). In the WCT, the primary task is air warfare management. While performing the air warfare task, task difficulty and task load are manipulated by changing the number of tracks per wave and the number of more difficult "yellow" tracks. We explored in this paper, the correlation between cognitive task load, the subject\´s performance and dorsolateral prefrontal cortex oxygenation level changes. Our data analysis results show that fNIR blood oxygenation changes are significantly sensitive to wave size (task load) changes.