Table 5.

Functional near-infrared spectroscopy (fNIRS)-BCI studies using the initial dip.

Reference	Paradigm	Brain area	Features	Window size	Classifier	Commands	Accuracy
Zafar and Hong, 2017	Mental arithmetic, mental counting, and puzzle solving tasks	Prefrontal cortex	Signal mean, minimum, signal slope, skewness, and kurtosis of ΔHbO	2.5 s	LDA	3	57.5% using signal mean and minimum values
Li et al., 2017	Left and right hand grasping tasks	Motor cortex	Mean ΔHbO and ΔHbR for fNIRS and wavelet coefficient for EEG	2 s	SVM	2	85.5% for fNIRS and 91.0% for hybrid EEG-fNIRS
Khan and Hong, 2017	Mental arithmetic, mental counting, mental rotation and word generation tasks	Prefrontal cortex	Signal peak, minimum, and signal mean of ΔHbO	2 s	LDA	4	75.6%
Zafar and Hong, 2018	Right-hand thumb and little finger tapping	Left motor cortex	Signal mean and minimum value of ΔHbO	2.5 s	LDA	2	74.9%

LDA, linear discriminant analysis; SVM, support vector machine.