fNIRS Functional Near Infrared Optical Brain Imaging

About fNIRS Technology

Continuous Wave fNIRS imaging offers researchers a portable functional near-infrared (fNIR) imaging research tool capable of monitoring brain’s hemodynamics and thereby the cognitive state of the subject in natural environments. fNIRS technology employs specific wavelengths in an optical frequency window which can easily pass through a few centimeters for most tissue, and allow monitoring blood oxygenation changes but monitoring back-scattered light intensity. The relative changes of light intensity across time are due to changes in oxy- and deoxy-hemoglobin and provides information about neural activity.

• fNIR FAQ—answers to frequently asked questions
• fNIR articles (PDF) and Citations
• fNIR Features & Benefits Brochure
• fNIRS Webinars On Demand
  • fNIRS | Studying Cognitive Function
  • fNIRS | How to Get High-Quality Optical Brain Imaging Data
  • fNIRS Applications and Solutions
  • fNIRS for Mental Workload Assessment
  • Multimodal Workload Measurements | Combining fNIRS, ECG/HRV, Eye Tracking & Stimulus Presentation
  • How to Add NIRS Labs for Brain Function and Muscle Oxygenation

• Introduction to fNIR Technology video article from Journal of Visualized Experiments

Comparison of fNIRS with other Neuroimaging Modalities

• Conventional Neuroimaging Techniques

  • Techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have been widely used for functional brain studies in humans.
  • These techniques are expensive, highly sensitive to motion artifacts, confine the participants to restricted positions, and may expose individuals to potentially harmful materials (PET) or loud noises (fMRI).
  • These characteristics make these imaging modalities unsuitable for many uses, including the monitoring of ongoing cognitive activity under routine working conditions.

• fNIRS Neuroimaging Solution for Natural Environments

  • fNIRS is the only stand-alone and field-deployable technology able to determine localized brain activity.
  • fNIRS can be readily integrated with other physiological and neurobehavioral measures that assess human brain activity, including eye tracking, pupil reflex, respiration and electrodermal activity. fNIRS can also complement other techniques.
  • Studies have shown a positive correlation between a participant’s performance and fNIRS responses as a function of task load.
  • It has also been shown that fNIRS can effectively monitor attention and working memory in real-life situations.

 

fNIRS is a powerful near-infrared spectroscopy imaging tool for in-lab cognitive tests and neuromarketing. This technique measures NIR light absorbance in blood of hemoglobin with and without oxygen and provides information about ongoing brain activity similar to functional MRI studies. It eliminates many of the drawbacks of fMRI and provides a safe, affordable, noninvasive solution for cognitive function assessment. The technology empowers researchers by providing greater flexibility for study design, including working within complex lab environments and operating in non-traditional lab locations for field studies (neuromarketing). The fNIR device provides relative change in hemoglobin levels, calculated using a modified Beer-Lambert law.

• Oxygenated hemoglobin change: delta O2Hb (µmol/L)
• Deoxygenated hemoglobin change: delta HHb (µmol/L)
• Total hemoglobin change: delta cHb (µmol/L)

fNIR data combines with physiological signals acquired through BIOPACs data acquisition and analysis systems such as ECG, respiration, cardiac output, blood pressure, electrodermal activity and stimulus response markers; AcqKnowledge^® software provides automated analysis tools for event related potentials and ensemble averaging. The system interfaces with most stimulus presentation systems (such as E-Prime or SuperLab) and BIOPAC’s range of Virtual Reality systems.

Select application areas

• Cognitive Function Monitoring: Studies reported that fNIR can effectively and reliably monitor attention and working memory and the results are in agreement with fMRI and EEG studies.
• Human Performance Assessment: Studies have shown a positive correlation between a participant’s performance and fNIR responses as a function of task load. Cognitive workload is quantitatively assessed by the fNIR system in real-life settings.
• Clinical Settings—Awareness During General Anesthesia: fNIR can monitor dept of anesthesia in OR conditions.
• Aging: The studies reported use of fNIR device in Aging research and usability of the device while patients are walking.

Key technical principles

• The fNIR functional imaging technique gives information about the hemodynamic activity of the cerebral cortex directly underlying a specified emitter-detector pair; emitter-signal localization is well defined and measured light intensity reveals the association with hemodynamic changes within ~1-1.5 cm distance from center of emitter-detector arrangement.
• The fNIR system uses Modified Beer-Lambert law to determine oxygenated hemoglobin (oxyHb), deoxygenated hemoglobin (deoxyHb)
• The light source for the current fNIR instrument uses light emitting diodes (LEDs) which provide a very compact wavelength light source. The system deploys two specific wavelengths, 730 nm and 850 nm sensitive to oxyHb and deoxyHb.
• fNIR systems provide raw light intensities in addition to oxyHb and deoxyHb.

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