This study was performed to investigate the usefulness of functional near-infrared spectroscopy (fNIRS) by conducting a comparative analysis of hemodynamic activation detected by fNIRS and positron emission tomography (PET) and magnetic resonance imaging (MRI) in patients with mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Participants were divided into four groups: the subjective memory impairment (SMI), amnestic MCI (aMCI), non-amnestic MCI (naMCI), and AD groups. We recorded the hemodynamic response during the semantic verbal fluency task (SVFT) using a commercial wireless continuous-wave NIRS system. The correlation between the parameters of the neuroimaging assessments among the groups was analyzed. Region of interest-based comparisons showed that the four groups had significantly different hemodynamic responses during SVFT in the bilateral dorsolateral prefrontal cortex (DLPFC). The linear mixed effect model result indicates that the mean ΔHbO2 from the bilateral DLPFC regions showed a significant positive correlation to the overall FDG-PET after controlling for age and group differences in the fNIRS signals. Amyloid PET signals tended to better differentiate the AD group from other groups, and fNIRS signals tended to better differentiate the SMI group from other groups. In addition, a comparison between the group pairs revealed a mirrored pattern between the hippocampal volume and hemodynamic response in the DLPFC. The hemodynamic response detected by fNIRS showed a significant correlation with metabolic and anatomical changes associated with disease progression. Therefore, fNIRS may be considered as a screening tool to predict the hemodynamic and metabolic statuses of the brain in patients with MCI and AD.

Background. As the elderly population and the prevalence of dementia increase, the importance of cognitive training for dementia prevention is being emphasized. To increase accessibility to cognitive training programs among elderly individuals, the InBrain Trainer (IBT), a smartphone application–based cognitive training including 12 cognitive tasks covering language, calculation, memory, attention, visuospatial function, and frontal/executive function was developed. The purpose of this study was to examine the effectiveness of the IBT by investigating cognitive improvement and prefrontal cortex activation in non-demented older adults using functional near-infrared spectroscopy (fNIRS). Methods. The IBT, an android-based cognitive training software program, was downloaded to the participant’s smartphone or tablet computer and administered at home. Non-demented older adults (51 intervention participants, 50 control participants) were enrolled in this study. The IBT consisted of 12 tasks derived from two tasks each for six cognitive domains. Each task has 4 difficulty levels, and 48 blocks (12 tasks × 4 levels) were used to frame the amount of cognitive tasks for ≥1.5 hours per day, 5 days per week, for 16 weeks. The intervention group received gradually increasing difficulty tasks as homework through a mobile phone application for 16 weeks. To verify the effectiveness of the IBT as the outcome measure, the InBrain Cognitive Screening Test (CST), fNIRS, and various scales were compared between the intervention and control groups at two time points (baseline and after 16 weeks of cognitive training). Results. Among 101 participants, 85 non-demented older adults (84.1%) completed the study protocol and were included in the final analysis, including 41 (80.3%) in the cognitive intervention group and 44 (88.0%) in the control group. The group-by-time interaction effect was significant only in the language domain score of the InBrain CST. When the language domain subtest scores were analyzed, significant interaction effects were presented in the phonemic generative naming test but not in the semantic generative naming test or the Difficult Naming Test. In the hemodynamic response of the prefrontal cortex measured by all channels of fNIRS, the group-by-time interaction effect was significant only in the dorsolateral prefrontal cortex during the Stroop incongruent task. There were no group-by-time interaction effects in the second outcome measures of various scales. Conclusion. Our study is meaningful in that cognitive training software implemented as an application on personal devices such as smartphones and tablet computers led not only to cognitive enhancement, but also increased prefrontal lobe activation. Therefore, cognitive training applications including the IBT are expected to provide effective cognitive intervention without time or space constraints both in a clinical setting and at home.

Objective Research on neural correlates in the prefrontal cortex (PFC) associated with self-injurious behavior has mainly been performed in adults. However, studies on adolescents are scarce. We aimed to investigate the activation and connectivity of the PFC between adolescents with self-injurious behavior (ASI) and psychiatric controls (PC) using functional near-infrared spectroscopy (fNIRS).Methods We used an emotion recognition task during fNIRS to assess 37 adolescents (23 with self-injurious behavior and 14 PC) between June 2020 and October 2021 and compared connectivity and activation between the two groups. We also measured adverse childhood events (ACE, Adverse Childhood Experiences) and performed a correlation analysis of channel activation according to ACE total scores.Results The difference in activation between the groups was not statistically significant. The connectivity of channel 6 was statistically significant. The interaction between channel 6 and the ACE total score showed statistical significance between the two groups(t[33] -2.61; p=0.014). The ASI group showed a negative correlation with the total ACE score.Conclusion This is the first study to investigate PFC connectivity using fNIRS in ASI. It has the implication of a novel attempt with a practically useful tool to uncover neurobiological differences among Korean adolescents.

Objective: Numerous studies have identified hemodynamic changes in adults with major depressive disorder (MDD) by using functional near-infrared spectroscopy (fNIRS). However, studies on adolescents with MDD are limited. As adolescence is a stage of rapid brain development, differences may occur depending on age. This study used fNIRS as an objective tool to investigate hemodynamic changes in the frontal lobe according to depression severity and age in adolescents with MDD. Methods: Thirty adolescents (12 aged 12−15 years and 18 aged 16−18 years) were retrospectively investigated. The Children's Depression Inventory was used as a psychiatric evaluation scale, fNIRS was used as an objective brain function evaluation tool, and the Verbal Fluency Test was performed. Results: During the Verbal Fluency Test, in the younger MDD group, oxygenated-hemoglobin concentration increased in the right dorsolateral prefrontal cortex region as the severity of depression increased. In the older MDD group, the oxygenated-hemoglobin concentration decreased in the right dorsolateral prefrontal cortex region as the severity of depression increased. Conclusion: These results suggest that fNIRS may be an objective tool for identifying age differences among adolescents with MDD. To generalize the results and verify fNIRS as a potential biomarker tool, follow-up studies with a larger sample group should be conducted.