fNIRS Analysis — From Fundamentals to Advanced Methods

NIRx was founded by fNIRS researchers and provides a comprehensive set of analysis resources to support researchers at every level. This hub covers the full fNIRS analysis workflow: from understanding the physiological basis of the NIRS signal, through experimental design, to software selection, real-time processing, and multi-modal integration.

Fundamentals of fNIRS Analysis

Three aspects underpin fNIRS neuroimaging: near-infrared light penetrates human tissue; haemoglobin has oxygenation-dependent absorbing characteristics; and neuronal activation alters the brain's oxygen demand. Together these allow fNIRS to measure relative changes in cortical O₂Hb and HHb concentration, providing a non-invasive window into brain function.

Analysis Software Options

NIRS Toolbox — MATLAB-based tools for signal processing, visualisation, GLM, functional connectivity, and multi-modal analysis. Created by Dr Ted Huppert at the University of Pittsburgh. NIRx data automatically imports 3D probe and anatomical information, enabling a greater range of analyses.

Homer2 and Homer3 — Widely used fNIRS analysis packages supporting group analyses, configurable processing streams, and custom algorithm integration. All NIRx systems save in .nirs format for seamless import.

nirsLAB — NIRx's in-house analysis environment offering data inspection tools, statistical parametric mapping (SPM), and individual and group-level analysis in a GUI-based toolbox.

Real-Time and Multi-Modal Analysis

For BCI and neurofeedback applications, NIRx offers Turbo-Satori for real-time online fNIRS processing. For multi-modal studies combining fNIRS with EEG, fMRI, eye tracking, TMS, or tDCS, NIRx provides dedicated integration support and expert guidance through workshops and webinars.

FAQ

What analysis software is compatible with NIRx data?

NIRx data can be loaded into NIRS Toolbox, Homer2, Homer3, nirsLAB, Satori, and Turbo-Satori. NIRx systems save in both the proprietary NIRx format and the standard .nirs format for broad compatibility. NIRx data also uniquely auto-imports 3D probe and anatomical information into the NIRS Toolbox.

What is the difference between Homer2 and Homer3?

Homer2 has been in development since the early 1990s, while Homer3 was released in 2019. Both share a similar GUI and support group analyses and customisable processing streams. Users can integrate their own algorithms and access all functions at the script level in both versions.

What is nirsLAB?

nirsLAB is an in-house NIRx fNIRS analysis environment offering data inspection, statistical parametric mapping (SPM), and individual and group-level analysis in a GUI-based toolbox. It is available to download from NITRC.

How can I get support with fNIRS analysis?

NIRx regularly hosts webinars, in-person workshops, and remote walkthroughs on fNIRS analysis. Researchers can also contact the NIRx support team at support@nirx.net for guidance on experimental design and analysis methods specific to their application.

Is fNIRS suitable for real-time BCI and neurofeedback?

Yes. fNIRS is a strong candidate for BCI applications due to its robustness to muscle movement artefacts and suitability for realistic measurement environments. NIRx's Turbo-Satori software provides dedicated real-time fNIRS analysis for neurofeedback and BCI research.