fNIRS-BCI is a non-invasive brain-computer interface technology that uses near-infrared light to measure hemodynamic responses in the cerebral [cortex](/brain-regions/cortex). This page covers the mechanism of action, current development state, key companies, clinical evidence for neurodegenerative applications, and comparison to other BCI modalities. [@ferrari2012]
fNIRS-BCI is a non-invasive brain-computer interface technology that uses near-infrared light to measure hemodynamic responses in the cerebral cortex. This page covers the mechanism of action, current development state, key companies, clinical evidence for neurodegenerative applications, and comparison to other BCI modalities. [@cope1991]
fNIRS measures brain activity through the hemodynamic response — the change in blood oxygenation that follows neural activity. When [neurons](/entities/neurons) fire, they consume oxygen, triggering increased blood flow to the active region. This process, known as neurovascular coupling, creates detectable changes in the absorption of near-infrared light. [@vermeer2017]
fNIRS-BCI is a non-invasive brain-computer interface technology that uses near-infrared light to measure hemodynamic responses in the cerebral [cortex](/brain-regions/cortex). This page covers the mechanism of action, current development state, key companies, clinical evidence for neurodegenerative applications, and comparison to other BCI modalities. [@ferrari2012]
fNIRS-BCI is a non-invasive brain-computer interface technology that uses near-infrared light to measure hemodynamic responses in the cerebral cortex. This page covers the mechanism of action, current development state, key companies, clinical evidence for neurodegenerative applications, and comparison to other BCI modalities. [@cope1991]
fNIRS measures brain activity through the hemodynamic response — the change in blood oxygenation that follows neural activity. When [neurons](/entities/neurons) fire, they consume oxygen, triggering increased blood flow to the active region. This process, known as neurovascular coupling, creates detectable changes in the absorption of near-infrared light. [@vermeer2017]
| Advantage | Description | [@fnirs2022]
|-----------|--------------| [@fnirs2021]
| Portability | Lightweight wearable systems; can be used in ambulatory settings | [@fnirsbci2020]
| Motion Tolerance | More resistant to motion artifacts than EEG; suitable for rehabilitation | [@khan2021]
| Silent Operation | No electromagnetic interference; compatible with other devices | [@yeung2021]
| Cost-Effective | Significantly cheaper than MEG or fMRI systems | [@holper2012]
| Ease of Setup | Less preparation time than EEG; no gel required | [@herold2017]
| Long-Term Wear | More comfortable for extended use than wet EEG electrodes | [@aust2022]
| Limitation | Description | [@sala2019]
|------------|--------------|
| Slow Signal | Hemodynamic response lags neural activity by 2-5 seconds; limits response speed |
| Limited Depth | Only measures cortical surface; cannot access deep brain structures |
| Skin Tone Effects | Signal quality varies with skin pigmentation due to melanin absorption |
| Optical Path | Hair can interfere with optode-scalp contact |
| Spatial Resolution | Coarser than invasive BCIs or fMRI |
| Susceptibility to Motion | Although better than EEG, still affected by gross head movements |
| Feature | fNIRS | EEG | MEG | Invasive ECoG |
|---------|-------|-----|-----|--------------|
| Invasiveness | Non-invasive | Non-invasive | Non-invasive | Invasive |
| Signal Type | Hemodynamic | Electrical | Magnetic | Electrical |
| Temporal Resolution | 100-200 ms | <1 ms | <1 ms | <1 ms |
| Spatial Resolution | 1-2 cm | 2-3 cm | 1-2 cm | 1-2 mm |
| Depth Coverage | Cortical | Cortical | Cortical | Cortical + some depth |
| Motion Tolerance | High | Low | Very Low | Very High |
| Cost | $10K-50K | $1K-20K | $2-3M | $30K-100K |
| Portability | High | Very High | Very Low | Low |
fNIRS has shown promise in AD research through:
| Company | Product | Key Features |
|---------|---------|---------------|
| NIRx | NIRSport | Wearable, wireless, 8-32 channels |
| Shimadzu | LABNIRS | High-density, research-grade system |
| Hitachi | ETG-4000 | 52-channel continuous wave system |
| Artinis | OctaMon | Portable, 8-channel, battery-powered |
| Biopac | fNIR2000 | Integrated software, research use |
| Kernel | Flow | Next-gen wearable fNIRS (combined with EEG) |
The field of fNIRS-BCI is advancing rapidly with several key developments on the horizon:
fNIRS-BCI has shown promise in [Alzheimer's Disease](/diseases/alzheimers-disease) research:
In [Parkinson's Disease](/diseases/parkinsons-disease), fNIRS is used for:
fNIRS-BCI applications in [ALS](/diseases/amyotrophic-lateral-sclerosis):
fNIRS-BCI applications in FTD are emerging[@holper2012]:
fNIRS applications in Huntington's disease include[@herold2017]:
[@ferrari2012]: [Ferrari & Quaresima, A brief review on the history of human functional near-infrared spectroscopy (fNIRS) development and fields of application (2012)](https://doi.org/10.1016/j.neuroimage.2012.03.035)
[@cope1991]: [Cope, The application of near infrared spectroscopy to neurological testing (1991)](https://doi.org/10.1113/expphysiol.1991.sp003578)
[@vermeer2017]: [Vermeer et al., Near-infrared spectroscopy in stroke: From research to clinical application (2017)](https://doi.org/10.1177/2391467317693369)
[@khan2021]: [Khan et al., fNIRS-based brain-computer interfaces for motor rehabilitation after stroke (2021)](https://doi.org/10.3389/fnins
[@yeung2021]: [Yeung et al., Applications of fNIRS to cognitive neuroscience (2021)](https://doi.org/10.1016/j.neuroimage.2020.117530)
[@holper2012]: [Holper et al., Learning to walk: Functional near-infrared spectroscopy signals (2012)](https://doi.org/10.1016/j.neuroimage.2012.01.094)
[@herold2017]: [Herold et al., Functional near-infrared spectroscopy in neurology (2017)](https://doi.org/10.1159/000477487)
[@aust2022]: [Aust et al., Functional near-infrared spectroscopy in Parkinson's disease (2022)](https://doi.org/10.1002/mds.29171)
[@sala2019]: [Sala et al., fNIRS for assessing Alzheimer's disease (2019)](https://doi.org/10.1002/alz.12044)