Editorial: Advanced fNIRS Applications in Neuroscience and Neurological Disorders

Huiting Qiao^1,2*Dan Zhang³Wentian Dong⁴Daifa Wang²

• ¹Beihang University, Beijing, China
• ²Beihang University School of Biological Science and Medical Engineering, Beijing, China
• ³Tsinghua University, department of Psychological and Cognitive Sciences, Beijing, China
• ⁴Peking University Sixth Hospital, Beijing, China

The collected articles underscore that fNIRS is remarkably versatile, having been applied across a broad range of neurological and psychiatric conditions. On the neurodevelopmental front, a comprehensive review in this issue surveys fNIRS studies on numerous childhood disorders, including cerebral palsy, autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), and neonatal brain injuries (Wang Jing et al). In another original study, Bian et al. use fNIRS to monitor prefrontal cortex activity during verbal fluency tasks in children with ADHD. In a separate original study in this issue, Wang Jing et al. also employed fNIRS to investigate therapeutic effects, reporting that repetitive transcranial magnetic stimulation (rTMS) combined with standard care led to greater improvements in ADHD symptoms and prefrontal connectivity than standard care alone. fNIRS's unique advantages—such as safety, non-invasiveness, wearability, compatibility with other modalities, and tolerance for movement—make it especially suitable for pediatric populations, enabling safe and reliable monitoring of neural changes even in young or inattentive children undergoing neuromodulation (Gao et al.). In another domain, cognitive function and impairment stand to benefit from fNIRS innovations. Liu et al. explored healthy cognitive processing using fNIRS, showing that binocular color fusion—a demanding visual task—elicited significantly stronger prefrontal connectivity and higher activation than binocular rivalry. The study indicates that fNIRS can sensitively track advanced perceptual–cognitive processes. Ruan et al. demonstrated that combining fNIRS-derived cortical oxygenation features with plasma biomarkers markedly improved the ability to distinguish Alzheimer's disease from Lewy body dementia in older adults. Choi et al. used fNIRS as a cognitive assessment tool and found that a 6-month herbal medicine and acupuncture program in patients with mild cognitive impairment led to cognitive improvements accompanied by increased prefrontal activation. Given its strong motion-tolerant capability for monitoring brain activity during complex perceptual tasks, fNIRS was also applied to assess cortical activation in stroke survivors performing combined balance and cognitive tasks (He et al.). The results highlight fNIRS's ability to evaluate how cognitive load influences motor networks in rehabilitation scenarios, while allowing patients to perform upright activities that would be infeasible inside traditional neuroimaging scanners. Yang et al. further noted that fNIRS's high temporal resolution and portability complement fMRI's spatial precision. Such combined approaches enable robust brain mapping and extend neuroimaging to populations or settings impractical for fMRI alone, which is particularly valuable for research on cognitive mechanisms. Several contributions focus on using fNIRS in severe brain injury and coma, areas where traditional assessments fall short. Disorders of consciousness– such as coma, vegetative state, and minimally conscious state – present a diagnostic challenge because patients cannot communicate. Liang et al. used resting-state fNIRS to show that patients who later regained higher levels of consciousness exhibited stronger frontal–occipital connectivity than those who remained vegetative, demonstrating the technique's value for noninvasively probing residual brain networks and predicting outcomes. Zhang Tan et al. applied fNIRS to assess pain processing in disorders of consciousness patients and found minimal overt cortical activation but markedly enhanced connectivity among somatosensory, motor, and prefrontal areas, illustrating its sensitivity to coordinated network responses even in low-cooperation patients. Wang Nan et al. reviewed fNIRS applications in disorders of consciousness, highlighting its portability, real-time monitoring capability, and compatibility with interventions such as brain–computer interfaces and neuromodulation. Zhao et al. described a neuromodulation trial protocol employing fNIRS alongside EEG and behavioral assessments to track therapy-induced brain changes, underscoring its role as a safely repeatable bedside tool for patients unsuitable for conventional neuroimaging. In rehabilitation, fNIRS enables objective, motion-tolerant monitoring of brain activity in real-world therapeutic contexts. Zhang Junfeng et al. demonstrated that, unlike clinical scales, fNIRS can quantitatively evaluate rehabilitation efficacy, with increased cortical oxygenation and connectivity providing neurophysiological support for the effectiveness of post-stroke spasticity interventions. Xiao et al. showed that, despite normal behavioral balance metrics, fNIRS can detect subtle central changes and compensatory strategies in musculoskeletal pain disorders, offering a more sensitive indicator of postural control deficits than standard measures. Xu et al. reported that functional electrical stimulation during walking in hemiparetic stroke patients reduced contralesional premotor cortex activation, illustrating how wearable fNIRS can capture gait-related neural changes in over-ground settings. Expanding its application to orthopedic rehabilitation, Cao et al. used wireless fNIRS to reveal reduced frontal–parietal activation during stair climbing in patients three months after anterior cruciate ligament reconstruction, suggesting neuroplastic changes following knee injury. In psychiatry, fNIRS offers a non-invasive, portable, and task-compatible means to detect disorder-specific neural alterations in populations often difficult to assess with conventional neuroimaging. Zhang Jiaxin et al. showed that schizophrenia patients with auditory hallucinations display altered frontotemporal activation patterns during verbal fluency, demonstrating fNIRS's ability to capture symptom-specific brain dysfunction. Ding et al. reported that patients with depression, anxiety, or insomnia exhibit distinct reductions in task-based prefrontal connectivity, supporting fNIRS as a tool for differentiating executive deficits across heterogeneous psychiatric disorders. Chen Danni et al. developed a free-association semantic task for perinatal depression, revealing prefrontal oxyhemoglobin changes that correlate with symptom severity, highlighting its applicability in low-cooperation populations. In postpartum women, Chen Xia et al. further linked insomnia-related disruptions in prefrontal–temporal connectivity and network efficiency to mood symptoms, illustrating how real-time, portable fNIRS monitoring can uncover subclinical brain changes outside traditional laboratory environments. Beyond clinical and laboratory contexts, Si et al. demonstrated the feasibility of a wearable fNIRS oximeter for continuous monitoring of cerebral oxygen saturation in participants during high-altitude expeditions. Such monitoring is critical for preventing brain injuries associated with both acute and chronic high-altitude exposure. The findings highlight fNIRS's robustness under extreme, mobile conditions and its potential for managing brain oxygenation in environmental or exercise-related challenges, thereby extending neuromonitoring well beyond the confines of the clinic. Taken together, the contributions in Advanced fNIRS Applications in Neuroscience and Neurological Disorders demonstrate that fNIRS has come of age as a mainstream neuroimaging modality. No longer a niche technique, it is now shedding new light on brain function across ages and disorders – from illuminating the underpinnings of childhood ADHD and autism, to tracking recovery in stroke and disorders of consciousness, to augmenting our ability to diagnose subtle cognitive impairment. The key message of this editorial collection is that fNIRS's non-invasiveness and portability are more than mere conveniences—they are gateways to groundbreaking research avenues and transformative clinical applications. In the years ahead, fNIRS is poised to play an increasingly vital role in both research and clinical practice, driving progress in brain science and improving outcomes for individuals with neurological and psychiatric conditions.