Effect of fNIRS on Physiological Index and Performance Under Vibratory Stimulus
Authors: Junya Sugimoto a, Hiroshi Hagiwara b
Abstract: Many traffic accidents are caused by human error. In order to help prevent human such error, we investigated brain hemodynamics in both the frontal and the somatosensory areas by functional near-infrared spectroscopy (fNIRS), electrocardiogram (ECG), and the following two types of task performance with vibratory stimulation: a Tracking task and the Stroop test. To evaluate changes in oxygenated hemoglobin concentration (oxyHb), we used δoxyHb as previously defined (H. Iwasaki: Availability and future prospects of functional near-infrared spectroscopy in usability evaluation, Human Factors and Ergonomics). Briefly, the waveform data of oxyHb are passed through a differential filter. A sum of more than zero is defined as a positive component, whereas a sum of less than zero is defined as a negative component. δoxyHb is defined as a positive component minus a negative component. δoxyHb > 0 indicates an increasing trend of oxyHb and δoxyHb < 0 indicates a decreasing trend of oxyHb. Our results show that tracking error and the variance of tracking error were reduced when vibratory stimulation was present. Marginally statistically significant (p < 0.1) differences for both tracking and Stroop indices were observed when comparing measures with and without vibratory stimulation. These results suggest that subjects were able to track targets more stably with than without vibratory stimulation. On the other hand, performance on the Stroop test (reaction time, variance of Stroop test, and percentage of correct answers) was not affected by vibratory stimulation. ECG HF (high frequency) in both tasks was lower with than without vibratory stimuli. ECG LF (low frequency)/HF in both tasks was higher with than without vibratory stimuli. The results of HF and LF/HF stimulation imply the predominance of both the sympathetic nervous system during vibratory stimulation and the parasympathetic nervous system with no stimulus. δoxyHb showed differences in the somatosensory area during the Tracking task between vibratory stimulation and no stimulation. In summary, presentation of vibratory stimuli improved performance in the Tracking task. Therefore, use of vibratory stimulation during driving may decrease traffic accidents caused by human error.
Keywords: fNIRS, vibratory stimulus, somatosensory area, monotonous task
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