Noxious electrical stimuli elicited a significantly higher oxygenated hemoglobin response in the primary somatosensory cortex compared to innocuous stimuli (p=0.008), supporting fNIRS as an objective measure of pain.
p-value: p=0.008
Assessing pain in individuals not able to communicate (e.g. infants, under surgery, or following stroke) is difficult due to the lack of non-verbal objective measures of pain. Near-infrared spectroscopy (NIRS) being a portable, non-invasive and inexpensive method of monitoring cerebral hemodynamic activity has the potential to provide such a measure. Here we used functional NIRS to evaluate brain activation to an innocuous and a noxious electrical stimulus on healthy human subjects (n = 11). For both innocuous and noxious stimuli, we observed a signal change in the primary somatosensory cortex contralateral to the stimulus. The painful and non-painful stimuli can be differentiated based on their signal size and profile. We also observed that repetitive noxious stimuli resulted in adaptation of the signal. Furthermore, the signal was distinguishable from a skin sympathetic response to pain that tended to mask it. Our results support the notion that functional NIRS has a potential utility as an objective measure of pain.
Yücel et al. (Mon,) conducted a other in Healthy subjects (pain response) (n=11). Noxious electrical stimulus vs. Innocuous electrical stimulus (subjective rating 3/10) was evaluated on Change in oxygenated hemoglobin (HbO) concentration in the primary somatosensory cortex at 4-6 seconds (p=0.008). Noxious electrical stimuli elicited a significantly higher oxygenated hemoglobin response in the primary somatosensory cortex compared to innocuous stimuli (p=0.008), supporting fNIRS as an objective measure of pain.
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