NICA: A Novel Toolbox for Near-Infrared Spectroscopy Calculations and Analyses.

Philipp Raggam,Selina C. Wriessnegger,Günther Bauernfeind

doi:10.3389/fninf.2020.00026

Abstract

Functional near-infrared spectroscopy (fNIRS) measures the functional activity of the cerebral cortex. The concentration changes of oxygenated (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) can be detected and associated with activation of the cortex in the investigated area (neurovascular coupling). Recorded signals of hemodynamic responses may contain influences from physiological signals (systemic influences, physiological artifacts) which do not originate from the cerebral cortex activity. The physiological artifacts contain the blood pressure (BP), respiratory patterns, and the pulsation of the heart. In order to perform a comprehensive analysis of recorded fNIRS data, a proper correction of these physiological artifacts is necessary. This article introduces NICA – a novel toolbox for near-infrared spectroscopy calculations and analyses based on MATLAB. With NICA it is possible to process and visualize fNIRS data, including different signal processing methods for physiological artifact correction. The artifact correction methods used in this toolbox are common average reference (CAR), independent component analysis (ICA), and transfer function (TF) models. A practical example provides results from a study, where NICA was used for analyzing the measurement data, in order to demonstrate the signal processing steps and the physiological artifact correction. The toolbox was developed for fNIRS data recorded with the NIRScout 1624 measurement device and the corresponding recording software NIRStar.

Highlights

Functional near-infrared spectroscopy is a non-invasive optical method for detecting functional hemodynamic activity of the cerebral cortex
The values of the concentration changes of oxy-Hb and deoxyHb, for each channel at each time point, are saved in a Microsoft Excel file, where they can be used for further statistical analysis
The surface of the graphical user interface (GUI) is divided into panels, which make it easy for the user to set and change different analysis settings that can be saved and loaded for individual studies

Summary

Introduction

Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical method for detecting functional hemodynamic activity of the cerebral cortex This method measures the regional changes of the oxygen concentration in the blood, more precisely the concentration changes of oxygenated (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb; Jöbsis, 1977; Wolf et al, 2007; Scholkmann et al, 2014). Using the (modified) Beer–Lambert law, it is possible to calculate the concentration changes in oxy-Hb and deoxy-Hb according to the attenuation of the intensity of the near-infrared light between the source and the detector (Coyle et al, 2007) With these concentration changes, conclusions about metabolic changes in the investigated area can be drawn, which are associated with brain activity (Malonek and Grinvald, 1996; Wolf et al, 2002)

Methods

Results

Conclusion