The Potential of Functional Near-Infrared Spectroscopy-Based Neurofeedback—A Systematic Review and Recommendations for Best Practice

Abstract

Background: The effects of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI)-neurofeedback on brain activation and behaviors have been studied extensively in the past. More recently, researchers have begun to investigate the effects of functional near-infrared spectroscopy-based neurofeedback (fNIRS-neurofeedback). FNIRS is a functional neuroimaging technique based on brain hemodynamics, which is easy to use, portable, inexpensive, and has reduced sensitivity to movement artifacts. Method: We provide the first systematic review and database of fNIRS-neurofeedback studies, synthesizing findings from 22 peer-reviewed studies (including a total of N = 441 participants; 337 healthy, 104 patients). We (1) give a comprehensive overview of how fNIRS-neurofeedback training protocols were implemented, (2) review the online signal-processing methods used, (3) evaluate the quality of studies using pre-set methodological and reporting quality criteria and also present statistical sensitivity/power analyses, (4) investigate the effectiveness of fNIRS-neurofeedback in modulating brain activation, and (5) review its effectiveness in changing behavior in healthy and pathological populations. Results and discussion: (1–2) Published studies are heterogeneous (e.g., neurofeedback targets, investigated populations, applied training protocols, and methods). (3) Large randomized controlled trials are still lacking. In view of the novelty of the field, the quality of the published studies is moderate. We identified room for improvement in reporting important information and statistical power to detect realistic effects. (4) Several studies show that people can regulate hemodynamic signals from cortical brain regions with fNIRS-neurofeedback and (5) these studies indicate the feasibility of modulating motor control and prefrontal brain functioning in healthy participants and ameliorating symptoms in clinical populations (stroke, ADHD, autism, and social anxiety). However, valid conclusions about specificity or potential clinical utility are premature. Conclusion: Due to the advantages of practicability and relatively low cost, fNIRS-neurofeedback might provide a suitable and powerful alternative to EEG and fMRI neurofeedback and has great potential for clinical translation of neurofeedback. Together with more rigorous research and reporting practices, further methodological improvements may lead to a more solid understanding of fNIRS-neurofeedback. Future research will benefit from exploiting the advantages of fNIRS, which offers unique opportunities for neurofeedback research.

Prefrontal Asymmetry BCI Neurofeedback Datasets

“…The RAP dataset is closer to previous EEG experiments (Cavazza et al, 2014) and the one with perhaps the most potential for confounding various aspects of PFC asymmetry in terms of its dimensional interpretation (approach, valence). On the other hand, it has some of the longest fNIRS NF epochs (Kohl et al, 2020) and is a good candidate to study signal dynamics.…”

“…In this section, we are briefly discussing the relevance and potential community interest of our datasets, considering the increasing popularity of fNIRS and in particular fNIRS NF. We will be basing this discussion primarily on the recent review of fNIRS NF by Kohl et al (2020), which collected a significant FIGURE 2 | (A) Overview of the apparatus used in our experiments: fNIR Optical Brain Imaging System (fNIR400) by Biopac Systems with one PC dedicated to the data acquisition, and one PC dedicated to running the simulation and visualization of the stimulus presented in real-time to the subjects. (B) The 16-channel sensor placed on the subjects' forehead (C) showing the selected channels for the calculation of the asymmetry values.…”

“…The duration of NF epoch in Kohl et al (2020) ranges from 5 to 40 s (the latter actually corresponding to our own RAP dataset, although its actual useful duration is 33 s), with the majority of epochs (30%) lasting 30 s. Our subject population was primarily drawn from healthy subjects, which were also overrepresented in Kohl et al (2020)'s review (76%). Our target RoI also proves to be one of the most studied ones, as 59% of the studies reviewed trained participants to regulate parts of the PFC.…”

“…Among the various neural signals that support BCI, the availability of fNIRS dataset remains scarce (Bak et al, 2019), despite its growing popularity, both for BCI (Naseer and Hong, 2015) and NF applications (Kohl et al, 2020).…”

Optical brain imaging and its application to neurofeedback

“…While recently published studies support the potential of f NIRS-neurofeedback for clinical and non-clinical applications, a recent systematic review concluded that sufficiently powered studies and large randomized controlled trials are still lacking and specificity of the reported effects remains to be demonstrated ( Kohl et al, 2020 ). Also, shortcomings in reporting important information were identified.…”