Fig. 4From: Functional near-infrared spectroscopy can detect low-frequency hemodynamic oscillations in the prefrontal cortex during steady-state visual evoked potential-inducing periodic facial expression stimuli presentationThe frequency domain grand-averaged LFHO signals across all conditions and participants during periodic FE stimuli with SSVEP. The unit of x-axis is Hz in frequency while the y-axis has no unitsBack to article page