Neural NoiseFunctional near-infrared spectroscopy (fNIRS) is a non-invasive optical neuroimaging technique that measures changes in cerebral oxygenation by detecting the differential absorption of near-infrared light by oxygenated and deoxygenated hemoglobin. The technique exploits the relative transparency of biological tissue to light in the 650-950 nm wavelength range to probe cortical hemodynamic responses associated with neural activity.
fNIRS offers several practical advantages over other neuroimaging modalities: it is portable, relatively inexpensive, tolerant of motion artifacts, and safe for repeated use. These characteristics make it particularly suitable for studying populations and conditions where fMRI is impractical, including infants, freely moving subjects, and naturalistic social interactions. fNIRS has also attracted interest as a bci-and-neural-decoding input modality, though its temporal resolution is limited by the hemodynamic delay.
Advances in source-detector array design, diffuse optical tomography algorithms, and hybrid fNIRS-eeg systems are extending the capabilities of near-infrared spectroscopy for brain research and clinical applications including intraoperative monitoring, neonatal brain health assessment, and cognitive workload measurement.