The potential role of functional near-infrared spectroscopy as clinical biomarkers in schizophrenia

Functional near-infrared spectroscopy (fNIRS) is a recently developed technique that can measure hemoglobin changes in the cerebral cortex, and fNIRS-based research in psychiatry has been progressing rapidly. fNIRS is advantageous in its noninvasiveness, ease of administration, tolerance of small movements, inexpensiveness, strong signal correlations with fMRI signals, and in providing imaging with excellent time resolution and moderate spatial resolution. However, fNIRS has several disadvantages, such as low spatial resolution and shallower measurements in brain regions compared with other functional neuroimaging techniques (e.g. functional magnetic resonance imaging and positron emission tomography). Therefore, fNIRS may be a candidate instrument for clinical use in psychiatry, as it can measure brain activity in a clinical setting. Moreover, previous studies have demonstrated that altered brain activity in the prefrontal cortex is associated with clinical symptoms and functional outcomes in patients with schizophrenia, suggesting that fNIRS could be used as a potential biomarker. Future studies aimed at exploring fNIRS differences in different clinical stages, longitudinal changes, medication effects, variations during different cognitive task paradigms, cross-cultural comparisons, and applying more delicate statistical analytic methodologies are warranted to develop more accurate biomarkers that can be applied in clinical practice for differential diagnosis, monitoring symptoms, predicting functional outcomes, and the personalized decision regarding treatment options in patients with schizophrenia.