Facial Vibrotactile Stimulation Activates the Parasympathetic Nervous System: Study of Salivary Secretion, Heart Rate, Pupillary Reflex, and Functional Near-Infrared Spectroscopy Activity

Figure 5

The fNIRS data recorded in the frontal cortex. (a) A computerized numerical analysis of variations in oxyhemoglobin (oxy-Hb) concentration during RS, 89 Hz-face, 114 Hz-face, and Ah~ (“Ah~” phonation). Red (plus) and blue shading (minus) indicate differences in frontal cortex activation, whereas the white band indicates nonactivation. Numbers indicated the positions of LED probes (16 channels). (b) Red and blue waves indicate the typical example of oxy-Hb and deoxy-Hb concentrations in the channel 3. The first vertical line indicates the start line of the various stimuli and the end vertical line indicates the finish line. (c) Changes in fNIRS activities during 2 min between solid lines of various vibrotactile stimuli and vocalizing “Ah~” sounds.