Sub-optimal presentation of painful facial expressions enhances readiness for action and pain perception following electrocutaneous stimulation

Measuring pain or discomfort during routine nursing care in lightly sedated mechanically ventilated intensive care patients: A prospective preliminary cohort study

BACKGROUND

Pain is routinely measured on mechanically ventilated ICU patients. However, the tools used are not designed to discriminate between pain and non-pain discomfort, a distinction with therapeutic implications.

OBJECTIVES

To evaluate whether clinical measurement tools can discern both pain and non-pain discomfort.

METHODS

A prospective observational cohort study was conducted in a General ICU at a tertiary Medical Center in Israel. The Behavior Pain Scale (BPS) and Visual Analog Scale (VAS) of Discomfort were simultaneously assessed by a researcher and bedside nurse on thirteen lightly sedated patients during 71 routine nursing interventions in lightly sedated, mechanically ventilated, adult patients. Patients were asked whether they were in pain due to these interventions.

RESULTS

Statistically significant increases from baseline during interventions were observed [median change: 1.00 (-1-5), 1.5(-4-8.5), p < 0.001] as measured by BPS and VAS Discomfort Scale, respectively. BPS scores ranged between 4 and 6 when the majority (53 %) of the patients replied that they had no pain but were interpreted by the clinicians as discomfort. Endotracheal suctioning caused the greatest increase in BPS and VAS, with no statistically significant differences in BPS and VAS Discomfort Scale scores whether patients reported or did not report pain. A BPS>6 had a higher sensitivity and specificity to reported pain (accuracy of 76 %) compared to a BPS of 4-6.

CONCLUSIONS

Standard assessments are sensitive to pain caused by routine nursing care interventions. However, this study presents evidence that among lightly sedated ICU patients, moderate BPS scores could also measure non-pain discomfort. ICU nurses should be aware that signs of unpleasantness measured by a pain scale could reflect non-pain discomfort.

Brain responses to the vicarious facilitation of pain by facial expressions of pain and fear

Observing pain in others facilitates self-pain in the observer. Vicarious pain facilitation mechanisms are poorly understood. We scanned 21 subjects while they observed pain, fear and neutral dynamic facial expressions. In 33% of the trials, a noxious electrical stimulus was delivered. The nociceptive flexion reflex (NFR) and pain ratings were recorded. Both pain and fear expressions increased self-pain ratings (fear > pain) and the NFR amplitude. Enhanced response to self-pain following pain and fear observation involves brain regions including the insula (INS) (pain > fear in anterior part), amygdala, mid-cingulate cortex (MCC), paracentral lobule, precuneus, supplementary motor area and pre-central gyrus. These results are consistent with the motivational priming account where vicarious pain facilitation involves a global enhancement of pain-related responses by negatively valenced stimuli. However, a psychophysiological interaction analysis centered on the left INS revealed increased functional connectivity with the aMCC in response to the painful stimulus following pain observation compared to fear. The opposite connectivity pattern (fear > pain) was observed in the fusiform gyrus, cerebellum (I-IV), lingual gyrus and thalamus, suggesting that pain and fear expressions influence pain-evoked brain responses differentially. Distinctive connectivity patterns demonstrate a stronger effect of pain observation in the cingulo-insular network, which may reflect partly overlapping networks underlying the representation of pain in self and others.

Different priming effects of empathy on neural processing associated with firsthand pain and nonpain perception

The shared-representation model of empathy is still debated. One of the major questions is whether empathy-eliciting stimuli depicting others' pain selectively activate the representations of self-pain. To address this issue, we assessed the priming effects of empathy-eliciting pictures on firsthand pain and nonpain perception, as well as its associated neural processing. In Experiment 1, when compared with nonpainful pictures depicting individuals' body parts with no injury, participants primed by painful pictures showing individuals' body parts with injury reported higher ratings for perceived intensity, unpleasantness, and salience of nociceptive and auditory stimuli, but they only exhibited increased N2 amplitude in response to nociceptive stimuli. In Experiment 2, the results from another group of participants replicated the observations of Experiment 1 and validated the findings in the non-nociceptive somatosensory modality. Importantly, participants' concern ratings for priming pictures predicted their unpleasantness ratings for subsequent nociceptive stimuli, while participants' attention ratings predicted their unpleasantness ratings for subsequent auditory and tactile stimuli. This finding implies that empathy for pain might influence pain and nonpain perception via different psychological mechanisms. In summary, our findings highlight the existence of pain-selective representations in empathy for pain and contribute to a better understanding of the shared-representation model of empathy.

Pharmacological fMRI provides evidence for opioidergic modulation of discrimination of facial pain expressions

The endogenous opioid system is strongly involved in the modulation of pain. However, the potential role of this system in perceiving painful facial expressions from others has not been sufficiently explored as of yet. To elucidate the contribution of the opioid system to the perception of painful facial expressions, we conducted a double‐blind, within‐subjects pharmacological functional magnetic resonance imaging (fMRI) study, in which 42 participants engaged in an emotion discrimination task (pain vs. disgust expressions) in two experimental sessions, receiving either the opioid receptor antagonist naltrexone or an inert substance (placebo). On the behavioral level, participants less frequently judged an expression as pain under naltrexone as compared to placebo. On the neural level, parametric modulation of activation in the (putative) right fusiform face area (FFA), which was correlated with increased pain intensity, was higher under naltrexone than placebo. Regression analyses revealed that brain activity in the right FFA significantly predicted behavioral performance in disambiguating pain from disgust, both under naltrexone and placebo. These findings suggest that reducing opioid system activity decreased participants' sensitivity for facial expressions of pain, and that this was linked to possibly compensatory engagement of processes related to visual perception, rather than to higher level affective processes, and pain regulation.

The behavioral and neural findings of this psychopharmacological fMRI study shed light on a causal role of the opioid system in the discrimination of painful facial expressions, paving the way for further exploration of clinical implications in the domains of pain diagnosis and treatment, on the one hand, and future research on the relationship between basic socio‐perceptual processing and empathy, on the other.

A meta-analysis of neuroimaging studies on pain empathy: investigating the role of visual information and observers' perspective

Empathy relies on brain systems that support the interaction between an observer's mental state and cues about the others' experience. Beyond the core brain areas typically activated in pain empathy studies (insular and anterior cingulate cortices), the diversity of paradigms used may reveal secondary networks that subserve other more specific processes. A coordinate-based meta-analysis of fMRI experiments on pain empathy was conducted to obtain activation likelihood estimates along three factors and seven conditions: visual cues (body parts, facial expressions), visuospatial (first-person, thirdperson), and cognitive (self-, stimuli-, other-oriented tasks) perspectives. The core network was found across cues and perspectives, and common activation was observed in higher-order visual areas. Body-parts distinctly activated areas related with sensorimotor processing (superior and inferior parietal lobules, anterior insula) while facial expression distinctly involved the inferior frontal gyrus. Self- compared to other-perspective produced distinct activations in the left insula while stimulus- versus other-perspective produced distinctive responses in the inferior frontal and parietal lobules, precentral gyrus, and cerebellum. Pain empathy relies on a core network which is modulated by several secondary networks. The involvement of the latter seems to depend on the visual cues available and the observer's mental state that can be influenced by specific instructions.

Observers' impression of the person in pain influences their pain estimation and tendency to help

BACKGROUND

Estimation of a patient's pain may have a considerable impact on the level of care that patient receives. Many studies have shown that contextual factors may influence an observer's pain estimation. Here, we investigate the effect of an observer's impression of a person in pain and justification of his/her pain on the observer's pain estimation, tendency to help and perceived empathy.

METHODS

Thirty healthy individuals (half females) read scenarios aimed to manipulate the reader's impression of characters who ultimately were fired from their work (four positive characters and four negative; half females). Then they observed 1-s videos of four levels of pain expression (neutral, mild, moderate, strong) in those characters during an examination. Subsequently, they rated pain estimation, tendency to help and perceived empathy. Afterwards, they rated their likability of characters and how just they find the end of story.

RESULTS

People rated pain in positive characters higher than the pain in negative characters. They also expressed more tendency to help and a higher level of perceived empathy towards positive characters than negative characters. For the highest level of pain in positive characters, perceived injustice towards that person was the best predictor of the observer's pain estimation, tendency to help and perceived empathy. For negative characters, dislikeability was the best predictor of tendency to help and perceived empathy. Justification of their pain was a predictor of pain estimation and tendency to help.

CONCLUSION

Observers used different information to evaluate pain in positive and negative individuals.

SIGNIFICANCE

Observers' estimation of pain, perceived empathy and tendency to help biases by their understanding of the characteristics of the person in pain. In clinical settings, these biases may influence the quality of care and well-being of patients. Understanding the underlying mechanisms of these biases can help us improve the quality of care and control the effect of prejudices on pain assessment.