Functional near-infrared spectroscopy: A novel tool for detecting consciousness after acute severe brain injury

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 121; no. 36; p. e2402723121
• Main Authors: Kazazian, Karnig, Abdalmalak, Androu, Novi, Sergio L., Norton, Loretta, Moulavi-Ardakani, Reza, Kolisnyk, Matthew, Gofton, Teneille E., Mesquita, Rickson C., Owen, Adrian M., Debicki, Derek B.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 03.09.2024
• Subjects: Adult; Biological Sciences; Brain; Brain - diagnostic imaging; Brain - physiopathology; Brain Injuries - diagnostic imaging; Brain Injuries - physiopathology; Brain injury; Consciousness; Consciousness - physiology; Female; Functional Neuroimaging - methods; Head injuries; Humans; Information processing; Infrared spectra; Infrared spectroscopy; Male; Medical imaging; Mental task performance; Middle Aged; Near infrared radiation; Neuroimaging; Sensorimotor system; Sensory integration; Spatial discrimination; Spatial resolution; Spectroscopy, Near-Infrared - methods; Spectrum analysis; Young Adult; brain Injury; fNIRS; consciousness; coma
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2402723121

Recent advancements in functional neuroimaging have demonstrated that some unresponsive patients in the intensive care unit retain a level of consciousness that is inconsistent with their behavioral diagnosis of awareness. Functional near-infrared spectroscopy (fNIRS) is a portable optical neuroimaging method that can be used to measure neural activity with good temporal and spatial resolution. However, the reliability of fNIRS for detecting the neural correlates of consciousness remains to be established. In a series of studies, we evaluated whether fNIRS can record sensory, perceptual, and command-driven neural processing in healthy participants and in behaviorally nonresponsive patients. At the individual healthy subject level, we demonstrate that fNIRS can detect commonly studied resting state networks, sensorimotor processing, speech-specific auditory processing, and volitional command-driven brain activity to a motor imagery task. We then tested fNIRS with three acutely brain injured patients and found that one could willfully modulate their brain activity when instructed to imagine playing a game of tennis—providing evidence of preserved consciousness despite no observable behavioral signs of awareness. The successful application of fNIRS for detecting preserved awareness among behaviorally nonresponsive patients highlights its potential as a valuable tool for uncovering hidden cognitive states in critical care settings.