(J-375) Test-Retest Reliability of Multimodal Imaging by fNIRS-EEG in Humans

Introduction:: Neurovascular coupling is a mechanism that connects cerebral blood flow to electrical activity in the brain. This is an important process, indicating proper brain function, and can therefore be used as a biomarker for brain illness. Functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) are two imaging modalities that work simultaneously to measure neurovascular coupling. fNIRS is a device that measures the blood flow in the brain by detecting dynamics of oxygenated and deoxygenated hemoglobin, whereas EEG measures the electrical neuronal activity. Due to the ease of transportation, cost efficiency, and flexibility in clinical settings, these two noninvasive imaging devices have become suitable for measuring neurovascular coupling in patients with neurological conditions. In contrast with comparable devices such as fMRI, it remains unclear whether fNIRS is reliable with regard to the variability of the neurovascular coupling across individual and group levels, possibly confounded by variability due to placement of optical sources and detectors, quality of the recordings, and data analyzation techniques. Therefore, this study will investigate the multimodal fNIRS-EEG imaging techniques to determine the test-retest reliability of fNIRS, while measuring neurovascular coupling. More specifically, this study aims to design a procedure that eliminates any factors that may lead to potential inconsistencies within the data, collect and analyze fNIRS and EEG responses through motor and auditory stimulus tasks, and calculate the reproducibility of this simultaneous system.


Materials and Methods:: A NIRScout fNIRS system and ActiChamp EEG system were used to conduct this study. A total of 10 subjects were recruited and underwent two experimental visits spaced two to seven days apart. Each experimental visit consisted of six sessions: two resting, two motor, and two auditory sessions. Resting sessions consisted of six minutes of pure resting while staring at a cross in the center of the computer screen. In motor sessions, subjects were asked to perform seven blocks of 20-s guided right-hand fist clenching at 1 Hz with rest intervals of 30 s. For auditory sessions, subjects were at rest and underwent seven blocks of 20-s auditory stimulus with rest intervals of 30 s. For each subject during the experiment, a bite bar was used to stabilize the mouth and reduce jaw movements, measurements were taken in reference to the head to ensure exact placement of the cap each time, and the order of sessions were kept constant. After the sessions were completed, the data was processed and the reproducibility of motor and auditory responses were quantified in terms of linear correlation coefficients.


Results, Conclusions, and Discussions:: Results and Discussion: Currently, data has been analyzed for seven of the ten subjects and the results completed thus far are in terms of motor reliability data for oxygenated hemoglobin. According to previous studies’ R-value criteria, at a group level, fNIRS results for oxygenated hemoglobin in the motor-1 session have shown a fair reliability status, with an R-value of 0.44, while motor-2 session’s responses were slightly less than that in the motor-1session. The combined R-value for motors 1 and 2 resulted in good reliability, with an R-value of 0.50. It is important to consider that some of the subjects participating in the experimental sessions were noted to be drowsy or fall asleep, which has been shown to affect the data and impact the reliability status. Data analysis will continue until the completion of all ten subjects. Additionally, further statistical analysis will be performed to calculate the linear correlation coefficients for fNIRS oxygenated and deoxygenated hemoglobin in both motor and auditory responses.

Conclusion: This study has demonstrated that fNIRS-EEG is feasible for measuring neurovascular coupling in the brain. Specifically, our equipment has demonstrated adequate reliability through fNIRS motor responses. As data continues to be acquired and analyzed, this study will provide new insight into the reliability of simultaneous fNIRS-EEG. Additionally, it will further evaluate the candidacy of fNIRS imaging being a suitable technique to measure hemodynamic responses in patients.


Acknowledgements (Optional): : Research was funded and supported by the Undergraduate Research Opportunities Program at The University of Oklahoma, National Institute of General Medical Sciences (P20GM135009), National Science Foundation (RII Track-4 2132182), and 2022 IBEST-OUHSC Funding for Interdisciplinary Research Program.




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