Detection of primary RGB colors projected on a screen using fNIRS

In this study,functional near-infrared spectroscopy(fNIRS)is utilized to measure the hemodynamic responses(HRs)in the visual cortex of 14 subjects(aged 22–34 years)viewing the primary red,green,and blue(RGB)colors displayed on a white screen by a beam projector.The spatiotemporal characteristics of their oxygenated and deoxygenated hemoglobins(HbO and HbR)in the visual cortex are measured using a 15-source and 15-detector optode con¯guration.To see whether the activation maps upon RGB-color stimuli can be distinguished or not,the t-values of individual channels are averaged over 14 subjects.To¯nd the best combination of two features for classi¯cation,the HRs of activated channels are averaged over nine trials.The HbO mean,peak,slope,skewness and kurtosis values during 2–7 s window for a given 10 s stimulation period are analyzed.Finally,the linear discriminant analysis(LDA)for classifying three classes is applied.Individually,the best classi¯cation accuracy obtained with slope-skewness features was 74.07%(Subject 1),whereas the best overall over 14 subjects was 55.29%with peak-skewness combination.Noting that the chance level of 3-class classi¯cation is 33.33%,it can be said that RGB colors can be distinguished.The overall results reveal that fNIRS can be used for monitoring purposes of the HR patterns in the human visual cortex.