Sabin Khadka

Graduation Semester and Year




Document Type


Degree Name

Master of Science in Biomedical Engineering



First Advisor

Georgios Alexandrakis


Functional Near Infrared Spectroscopy (fNIRS) is a non-invasive functional neuroimaging technique, which measures changes in oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) concentrations based on the principle of near infrared spectroscopy. For my thesis, I have utilized fNIRS in the prefrontal regions to study cognitive functions under noxious pain and during a psychological test. The fNIRS signals were acquired from the prefrontal cortex (PFC) in order to investigate the hemodynamic response under noxious pain stimuli. The measurement consisted of two different visits separated by seven to ten days with two different levels of pain intensity. From the observations, PFC shows significant deactivation in response to higher noxious pain stimuli. Also, I observed that the temporal HbO profiles in contra-lateral PFC show significant differences in response to two pain stimuli. The response of HbO in medial anterior prefrontal cortex exhibits a better correlation with the behavioral pain rating in response to higher pain stimuli. The results reveal that the fNIRS is able to detect the hemodynamic activities in response to noxious pain stimuli and can be a potential neural correlate for cognitive evaluation of pain. In the second part of study, fNIRS signals were acquired from anterior prefrontal cortex (aPFC) in order to investigate the hemodynamic activity while performing a psychological test. A psychological test, called Stroop test, was used to investigate the activity in aPFC. Stroop test is a commonly used to investigate the attention and cognitive control of the brain. The fNIRS results have shown detectable activities in aPFC while performing the Stroop test. Also, as the difficulty of task increases or more attention is required, the changes in HbO are higher in right aPFC. Thus, the change in HbO in aPFC may be a potential neural correlate for human cognitive functions."


Biomedical Engineering and Bioengineering | Engineering


Degree granted by The University of Texas at Arlington