The might of light for revealing neuropsychiatric mechanisms

Human in vivo optical neuroimaging has strong potential to advance neuropsychiatric disease elucidation and treatment. Akin to functional magnetic resonance imaging (fMRI) for a proxy for brain hemodynamics and activity, functional near-infrared spectroscopy (fNIRS) systems apply two near-infrared wavelengths of light and read out reflections from the head to quantify real-time changes in hemoglobin oxygenation. Moreover, fNIRS measures are non-invasive, achieved using wearable devices, and have less movement sensitivity, facilitating feasibility and patient acceptability, and permitting measures in movement-prone populations, including children or individuals with movement disorders. Portable fNIRS devices permit study in ecologically salient environments, elucidating responses of brain systems subserving social processes in “real-world” settings. For example, fNIRS recently showed sensitivity in detecting differences in regional brain responses to in-person, compared to videoconferenced, face processing [1]. As social dysfunction is central to suffering and disability of psychiatric conditions, study in real-world settings may provide critical new information about disorder mechanisms that prior were elusive.

FNIRS’ feasibility also makes it amenable to repeated measurements to follow treatment response or disease progression. Temporal patterns of brain activity and related behaviors are increasingly thought to hold essential information about the pathophysiology of neuropsychiatric conditions [2] and can provide early indicators of worsening to prevent progression and improve prognosis.