Standard functional near-infrared spectroscopy parameters in young adults living in different regions of European Russia

BACKGROUND: In recent years, numerous studies have attempted to compare the results of functional near-infrared spectroscopy (fNIRS) obtained by different authors using various devices. To reach a consensus on standardizing fNIRS parameters, interpreting data, and ensuring reproducibility, comparative assessments of these parameters in healthy individuals from different geographical and climatic regions are needed. AIM: To characterize standard fNIRS parameters in young adults living in various environmental conditions. MATERIALS AND METHODS: The study included 100 clinically healthy Caucasian men and women aged 18–25 years, all native residents of three regions in European Russia: Arkhangelsk Oblast, Volgograd Oblast, and the Republic of Crimea. Hemodynamic responses of the cerebral cortex in the near-infrared range were assessed using the Cortivision Poton Cap C20 device (Cortivision, Poland). The experimental protocol consisted of three stages: Stage 1: baseline fNIRS recording with eyes open (30ʹ); Stage 2: administration of the following tasks: Simple Visual-Motor Reaction (2ʹ), Complex Visual-Motor Reaction (2ʹ), and Kraepelin Test (3ʹ); Stage 3: post-task fNIRS recording with eyes open (1ʹ). For subsequent data analysis, mean fNIRS values of HbO and HbR concentrations (mmol/L) were used for both the baseline and post-task stages. RESULTS: Comparative analysis of regional differences in baseline and post-task fNIRS values revealed no statistically significant differences between participants from the modeled regions, which varied considerably in environmental comfort scores (6 points for Arkhangelsk Oblast, 17 points for Volgograd Oblast, 25 points for the Republic of Crimea). At the same time, clear differences in the baseline expression of fNIRS parameters were observed between the sampled groups of male and female participants. Repeatedly observed unidirectional differences in baseline HbO and HbR concentrations between male and female participants were identified in the same cortical areas. In both cases, statistically significant differences in concentrations were identified in symmetrical frontal (AF4–AFp2, AF3–AFp1) and temporal (FTT8–T8, FTT7–T7) leads. In women, higher values were recorded in the frontal cortex, whereas in men, the concentrations of the studied forms of hemoglobin were higher in the temporal regions. CONCLUSION: The study characterized standard fNIRS parameters in young adults residing in varied environmental conditions. The presented data will contribute to improving the reliability and reproducibility of studies conducted using fNIRS technology, thereby facilitating the implementation of advanced neuroimaging methods in both research and clinical practice.