Frontal Lobe Hemodynamic Responses to Painful Stimulation: A Potential Brain Marker of Nociception

Abstract

The purpose of this study was to use functional near-infrared spectroscopy (fNIRS) to examine patterns of both activation and deactivation that occur in the frontal lobe in response to noxious stimuli. The frontal lobe was selected because it has been shown to be activated by noxious stimuli in functional magnetic resonance imaging studies. The brain region is located behind the forehead which is devoid of hair, providing a relative ease of placement for fNIRS probes on this area of the head. Based on functional magnetic resonance imaging studies showing blood-oxygenation-level dependent changes in the frontal lobes, we evaluated functional near-infrared spectroscopy measures in response to two levels of electrical pain in awake, healthy human subjects (n = 10; male = 10). Each subject underwent two recording sessions separated by a 30-minute resting period. Data collected from 7 subjects were analyzed, containing a total of 38/36 low/high intensity pain stimuli for the first recording session and 27/31 pain stimuli for the second session. Our results show that there is a robust and significant deactivation in sections of the frontal cortices. Further development and definition of the specificity and sensitivity of the approach may provide an objective measure of nociceptive activity in the brain that can be easily applied in the surgical setting.

Using prerecorded hemodynamic response functions in detecting prefrontal pain response: a functional near-infrared spectroscopy study

“…These findings are concordant with the findings reported in our previous papers 6,7 that the hemodynamic response to painful stimuli was stronger than that to nonpainful stimuli and that the response was most strongly present in the medial portion of the aPFC. The overall good test-retest reliability of aPFC response to pain on a single subject provides the basis of employing a prerecorded pain response function to detect subsequent perception of painful events.…”

“…Advantages of putting NIRS optodes on the forehead include the ease of access and the ability to eliminate hair contaminations to obtain a high signal-to-noise ratio. 7 Finally, it should be noted that machinelearning approaches usually require a large sample set to train classifiers to achieve a reasonable sensitivity and specificity. 40 In this fNIRS study, however, we showed that the detection sensitivity of pain response could be significantly improved just by adding a short prerecorded session (a 3-min acquisition containing three noxious stimuli) prior to the actual noxious scan.…”

“…1,2 NIRS is a noninvasive neuroimaging technique that is able to provide longterm measures of cortical hemodynamics [i.e., through measure of the changes of oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) concentrations]. [3][4][5] Previous work using fNIRS in studying pain mainly delineated a significant deoxygenation process (normally a decrease in HbO concentration) in the anterior prefrontal cortex (aPFC) in response to noxious stimuli, including cutaneous pain, [6][7][8] tooth pain, 9 and visceral pain. 10,11 Such observations are in line with recent reports of deactivations in aPFC blood oxygenation level-dependent (BOLD) signals following pain using functional magnetic resonance imaging (fMRI).…”

“…[12][13][14][15] Our previous fNIRS studies reported that the hemodynamic response to noxious stimuli was stronger than the response to innocuous stimuli with regard to peak amplitude changes 6 and that the HbO decrease is most strongly present in the medial portion of the aPFC. 7 Several difficulties remain regarding using the defined feature of the aPFC response (viz., the amplitude of HbO decrease) to detect pain in individual cases including: (1) the hemodynamic response to pain seems to show habituation with repetitive painful stimuli, leading to an insignificant difference in the response amplitude between innocuous stimuli and repeated noxious stimuli; 6,7 (2) distinct patterns in the shape of the hemodynamic response function (HRF) to pain (in terms of e.g., activations or deactivations, the peak/nadir time, dispersion, and undershoot time) have also been observed across different subjects, brain regions, and types of pain. In addition to the deactivations, multiple studies using fNIRS also reported pain-induced activations in the aPFC, largely in the lateral portion; [16][17][18][19] and (3) while the aPFC hemodynamic changes associated with pain were shown to be bilateral in some studies, others observed predominantly left-lateralized responses.…”

Somatosensory Response to Trigeminal Stimulation: A Functional Near-Infrared Spectroscopy (fNIRS) Study

“…The same preprocessing stream was used for experiment 1 and 2. Data preprocessing as well as hemodynamic response function (HRF) estimation was performed using the Windows version of Homer2 68 run in Matlab (R2016b, MathWorks, Inc., Natick, US) and followed a data processing stream used in a recent pain study 69 . In order to convert the raw data into a Homer2-compatible format an adapted version of a freely available Matlab script (by Dr. Dewey https://www.nitrc.org/projects/hitachi2nirs ) was used.…”