Facial Expressions Of Pain Research Articles

Representational momentum in dynamic facial expressions is modulated by the level of expressed pain: Amplitude and direction effects.

Humans have developed a specific capacity to rapidly perceive and anticipate other people's facial expressions so as to get an immediate impression of their emotional state of mind. We carried out two experiments to examine the perceptual and memory dynamics of facial expressions of pain. In the first experiment, we investigated how people estimate other people's levels of pain based on the perception of various dynamic facial expressions; these differ both in terms of the amount and intensity of activated action units. A second experiment used a representational momentum (RM) paradigm to study the emotional anticipation (memory bias) elicited by the same facial expressions of pain studied in Experiment 1. Our results highlighted the relationship between the level of perceived pain (in Experiment 1) and the direction and magnitude of memory bias (in Experiment 2): When perceived pain increases, the memory bias tends to be reduced (if positive) and ultimately becomes negative. Dynamic facial expressions of pain may reenact an "immediate perceptual history" in the perceiver before leading to an emotional anticipation of the agent's upcoming state. Thus, a subtle facial expression of pain (i.e., a low contraction around the eyes) that leads to a significant positive anticipation can be considered an adaptive process-one through which we can swiftly and involuntarily detect other people's pain.

Different patterns in mental rotation of facial expressions in complex regional pain syndrome patients.

Although facial pain expressions are considered to be the most visible pain behaviors, it is known that the association between pain intensity and facial pain expression is weak for chronic pain. The authors hypothesized that the facial pain expressiveness was altered in chronic pain and investigated it with a mental rotation task using various facial expression, which seems to be associated with actual facial movements. As a task stimulus, 4 types of facial expression stimuli consisted of upper (tightening of eye and furrowed brows) and lower (raising upper lip) pain-specific facial expressions, and upper (eyeball deviation) and lower (tongue protrusion) facial movements not using facial muscles were used. Participants were asked to judge whether a stimulus presented at various rotation angles was left- or right-sided. The authors tested 40 patients with complex regional pain syndrome (CRPS) (12 women, age range 21-60) and 35 healthy controls (15 women, age range 26-64). In an analysis of reaction time (RT) using a linear mixed model, patients were slower to react to all types of stimuli (P = .001) and a significant interaction between group (patient or control) and type of facial expression was observed (P = .01). In the post hoc analysis only patients showed longer RTs to raising upper lip than other types of facial expressions. This reflects a deficit in mental rotation tasks especially for lower facial region pain expressions in CRPS, which may be related to the psychosocial aspects of pain. However, comprehensive intra- and interpersonal influences should be further investigated.

Brain activity induced by implicit processing of others' pain and pleasure.

Studies indicate that both explicit and implicit processing of affectively charged stimuli may be reflected in specific behavioural markers and physiological signatures. Here, we investigated whether the pleasantness ratings of a neutral target were affected by the subliminal perception of a painful (a slap) or pleasant (a caress) touch delivered to others. In particular, we combined the continuous flash suppression technique with the affective misattribution procedure to explore subliminal processing of observed pain and pleasure in others. Results show that participants rated the neutral target as more or less likeable depending on whether they were subliminally primed with the pleasant or painful facial expression, respectively. The fMRI activity associated with painful and pleasant subliminal priming was mainly present in the anterior prefrontal cortex and the primary sensorimotor cortex, respectively. Thus, our study provides behavioural and neuro-physiological evidence that: (i) emotional reactivity toward positive or negative states of others can occur at an entirely subliminal level; (ii) specific neural substrates underpin reactivity to positive- and negative-valence of social emotions. Hum Brain Mapp 38:5562-5576, 2017. © 2017 Wiley Periodicals, Inc.

The role of spatial frequency information in the decoding of facial expressions of pain: a novel hybrid task.

Spatial frequency (SF) information contributes to the recognition of facial expressions, including pain. Low-SF encodes facial configuration and structure and often dominates over high-SF information, which encodes fine details in facial features. This low-SF preference has not been investigated within the context of pain. In this study, we investigated whether perpetual preference differences exist for low-SF and high-SF pain information. A novel hybrid expression paradigm was used in which 2 different expressions, one containing low-SF information and the other high-SF information, were combined in a facial hybrid. Participants are instructed to identify the core expression contained within the hybrid, allowing for the measurement of SF information preference. Three experiments were conducted (46 participants in each) that varied the expressions within the hybrid faces: respectively pain-neutral, pain-fear, and pain-happiness. In order to measure the temporal aspects of image processing, each hybrid image was presented for 33, 67, 150, and 300 ms. As expected, identification of pain and other expressions was dominated by low-SF information across the 3 experiments. The low-SF preference was largest when the presentation of hybrid faces was brief and reduced as the presentation duration increased. A sex difference was also found in experiment 1. For women, the low-SF preference was dampened by high-SF pain information, when viewing low-SF neutral expressions. These results not only confirm the role that SF information has in the recognition of pain in facial expressions but suggests that in some situations, there may be sex differences in how pain is communicated.

The effects of repeated nitroglycerin administrations in rats; modeling migraine-related endpoints and chronification

BackgroundRodent models typically use a single nitroglycerin injection to induce migraine, yet migraine in clinical populations presents as recurrent episodes. Further, these models quantify behavioral endpoints that do not align with the clinical features of episodic migraine or migraine chronification and therefore may limit translational relevance. New methodRats received 5 nitroglycerin (10mg/kg/2ml), propylene glycol/ethanol vehicle, or saline injections every third day over 15days. Behavioral endpoints were assessed 110min post nitroglycerin administration and included time spent light/dark chambers for photophobia as well as activity, facial pain expressions, and tactile allodynia. ResultsAnimals administered nitroglycerin displayed photophobia, decreased activity, and increased facial pain expression. Similar alterations in photophobia and activity were seen in the vehicle treated animals, but these tended to diminish by the 4th or 5th injection. The presentation of spontaneous tactile allodynia was observed in the nitroglycerin group by the 5th episode. Comparison with existing methodsMost NTG migraine models entail a single NTG administration and quantification of evoked allodynia. This paradigm employs recurring NTG episodes and clinically-relevant measures of photophobia, hypoactivity and facial grimace endpoints as well as introduces a novel arena apparatus to quantify spontaneous allodynia. ConclusionsThis repeated NTG procedure and endpoint measures aligns with the frequency and clinical presentation of episodic migraine and its chronification, respectively. Further, propylene glycol ethanol vehicle contributes to migraine endpoints.

The effect of tDCS over the right temporo-parietal junction on pain empathy

Empathy is a complex psychological phenomenon crucial for social perception and interactions. Several lines of evidence suggest that the right temporo-parietal junction is involved in self-other control mechanisms that play an important role in empathic responses. However, limited direct evidence of the involvement of this region in empathic responses is currently available. In this study, inhibitory transcranial direct current stimulation over this region influenced empathic responses to others’ pain. It was found that compared to participants that received anodal or sham transcranial direct current stimulation, participants who received cathodal transcranial direct current stimulation over the right temporo-parietal junction perceived the pain of others as less intense compared to sham stimulation and showed decreased late event related potentials to facial expressions of pain. Furthermore, it was found the stimulation had no significant effect on measures of sensorimotor resonance and physiological responses to pain in others. Our results demonstrate that the right temporo-parietal junction plays a role in empathic responses and that its inhibition can decrease behavioural and cerebral measures related to the cognitive-evaluative component of empathy. It is proposed that the right temporo-parietal junction is a valid stimulation target to study the influence of self-other control in empathic processes and could be useful to study the involvement of this region observed in clinical conditions characterized by altered empathic responses.

Estimating Pain and Disability in Virtual Patients with Low Back Pain: The Contribution of Nonverbal Behaviors

It is well recognized that chronic low back pain (cLBP) can be estimated from nonverbal pain behaviors. However, only a few studies examined how clinicians rely on those when estimating specific outcomes, such as pain intensity and pain disability. Therefore, the present study examines (1) if facial expressions and guarding behaviors (including speed of the movement and lifting strategy) contribute to the prediction of pain intensity and disability in patients with cLBP; and (2) if these pain behaviors have been given the same importance according to the outcome. Twenty-five experienced clinicians and thirty-one novice clinicians were asked to estimate low back pain intensity and disability from a realistic virtual character performing a lifting lowering task. The studied pain behaviors were manipulated across different conditions. Pain intensity and disability were judged higher when the character moved more slowly and displayed painful facial expression. Speed of the movement and facial expressions explained a greater portion of variance when related to pain intensity assessment than to pain disability assessment. Results also showed a significant interaction between the lifting strategy, the speed of the movement and facial expressions, but only when estimating the character’s pain-related intensity. Novice clinicians rated pain disability higher than experienced clinicians did. Although pain-related concepts, pain intensity and related disability are not estimated through the same pain behaviors by clinicians. Clinical experience does not contribute to clinical judgments through the use of nonverbal pain behaviors when estimating pain outcomes but contributes to pain disability rating overall.

Facial Pain Expression in Dementia: A Review of the Experimental and Clinical Evidence

The analysis of the facial expression of pain promises to be one of the most sensitive tools for the detection of pain in patients with moderate to severe forms of dementia, who can no longer self-report pain. Fine-grain analysis using the Facial Action Coding System (FACS) is possible in research but not feasible for clinical use at the moment because it is too time and effort consuming. Studies using the FACS showed either enhanced facial responses or no alterations of facial activity during pain in patients with cognitive impairment. Pain assessment in the clinical context relies strongly on the use of observational scales when self-report has become invalid. All of the established scales include items describing facial responses to pain. Despite this agreement, the content of these face items is very different, ranging from anatomically-based descriptions to inference of internal states. Recent studies let the anatomical orientation appear more promising. Automated video systems for the detection of pain in patients with dementia may lead to ground-breaking improvements of pain care in the future.

Increased Evoked Potentials and Behavioral Indices in Response to Pain Among Individuals with Intellectual Disability

Previous studies on the sensitivity and reactivity to pain of individuals with intellectual disability (ID) are inconsistent. The inconsistency may result from the reliance on self-reports and facial expressions of pain that are subject to internal and external biases. The aim was therefore to evaluate the reactivity to pain of individuals with ID by recording pain-evoked potentials (EPs), here for the first time, and testing their association with behavioral pain indices. Forty-one healthy adults, 16 with mild-moderate ID and 25 controls. Subjects received series of phasic heat stimuli and rated their pain on self-report scales. Changes in facial expressions and in pain EPs were recorded and analyzed offline. Pain self-reports, facial expressions, and the N2P2 amplitudes of the EPs exhibited stimulus-response relationship with stimulation intensity in both groups. The facial expressions and N2P2 amplitudes of individuals with ID were increased and N2P2 latency prolonged compared with controls. N2P2 amplitudes correlated with self-reports only in controls. Individuals with ID are hypersensitive/reactive to pain, a finding bearing clinical implications. Although pain EPs may reflect a somewhat different aspect of pain than the behavioral indices do, there is evidence to support their use to record pain in noncommunicative individuals, pending further validation.

Experiencing Pain in the Presence of Others: A Structured Experimental Investigation of Older Adults.

We showed that the presence of others influences the experience and expression of pain in older adults. The presence of a family member increases nonverbal pain expressiveness whereas the presence of a stranger results in decreased self-reported pain unpleasantness.

Understanding Facial Expressions of Pain in Patients With Depression.

The facial expression of pain in patients with depression indicates stronger affective pain processing and stronger association with self-report than in healthy individuals.

Monitoring equine (acute) pain: validation of two composite pain scales for general pain expression and facial expression of pain

Monitoring equine (acute) pain: validation of two composite pain scales for general pain expression and facial expression of pain

Facial Expressions of Pain and Pleasure are Highly Distinct

Facial Expressions of Pain and Pleasure are Highly Distinct

Child attention to pain and pain tolerance are dependent upon anxiety and attention control: An eye-tracking study.

Pain is common and can be debilitating in childhood. Theoretical models propose that attention to pain plays a key role in pain outcomes, however, very little research has investigated this in youth. This study examined how anxiety-related variables and attention control interacted to predict children's attention to pain cues using eye-tracking methodology, and their pain tolerance on the cold pressor test (CPT). Children aged 8-17years had their eye-gaze tracked whilst they viewed photographs of other children displaying painful facial expressions during the CPT, before completing the CPT themselves. Children also completed self-report measures of anxiety and attention control. Findings indicated that anxiety and attention control did not impact children's initial fixations on pain or neutral faces, but did impact how long they dwelled on pain versus neutral faces. For children reporting low levels of attention control, higher anxiety was associated with less dwell time on pain faces as opposed to neutral faces, and the opposite pattern was observed for children with high attention control. Anxiety and attention control also interacted to predict pain outcomes. For children with low attention control, increasing anxiety was associated with anticipating more pain and tolerating pain for less time. This is the first study to examine children's attention to pain cues using eye-tracking technology in the context of a salient painful experience. Data suggest that attention control is an important moderator of anxiety on multiple outcomes relevant to young people's pain experiences. This study uses eye tracking to study attention to pain cues in children. Attention control is an important moderator of anxiety on attention bias to pain and tolerance of cold pressor pain in youth.

Effects of Alzheimer Disease on the Facial Expression of Pain.

Facial expression may be a surrogate marker of pain in Alzheimer disease (AD) when self-report of pain is compromised. Recent studies have demonstrated increased pain sensitivity in AD; however, experimental pain studies analyzing facial expressions in AD are limited and report inconsistent results. The aims of this study were to examine facial expression of pain in AD patients and its relationship to sum-scored measures of multiple pain behavioral domains and subjective pain ratings. The Facial Action Coding System (FACS) was used to characterize facial expressions in 35 AD patients and 33 healthy seniors during pressure algometry. To improve pain specificity, facial responses were categorized as pain-relevant or pain-irrelevant before group analyses. We also assessed the relationship of AD severity to differential facial responsiveness by correlating FACS-based results with clinical pain scales (portions of the Pain Assessment in Advanced Dementia scale and the Faces Pain Scale-Revised [FPS-R]). No significant relationship was found between AD severity and FACS scores. Pain-relevant, but not irrelevant, FACS scores were increased in AD patients compared with seniors without AD. Pain Assessment in Advanced Dementia scale stimulus-response slopes were correlated with those of pain-relevant FACS and FPS-R in both the groups. Pain-relevant FACS slopes showed no relationship with those of the FPS-R in either group. Pain sensitivity is increased across all severities of AD when measured using the FACS. Clinical observational pain scales support the relevance of facial expression as a partial compensatory pain communication modality for AD. However, measures of pain behavior that sum across objective coding of several domains provide a better indicator of subjective pain than measures of facial expression alone.

Killian's photographs: "Facies dolorosa", the countenance of pain.

. The book “Facies dolorosa” by Hans Killian, first published in 1934 and later in 1956 and 1967 as extended and annotated versions, comprises ~ 70 photographs depicting facial expressions of patients suffering from various diseases. The photographs in black and white are analyzed and annotated by the author with the purpose of providing clinicians, and especially young doctors, with an insight into the medical and scientific value of facial expression of pain in the diagnosis, staging, and prognosis of severe disease. This historical review of a book no longer in print is part of a 2016 commemorative publication marking the 60th anniversary of the publication of the “Facies dolorosa” by Dustri Medical and Scientific Publications, Munich, Germany and Rockledge, USA.

Repeated exposure to vicarious pain alters electrocortical processing of pain expressions.

Repeated exposure to others in pain has been shown to bias vicarious pain perception, but the neural correlates of this effect are currently not known. The current study therefore aimed at measuring electrocortical responses to facial expressions of pain following exposure to expressions of pain. To this end, a between-subject design was adopted. Participants in the Exposure group were exposed to facial expressions of intense pain, while the participants in the Control group were exposed to neutral expressions before performing the same pain detection task. As in previous studies, participants in the Exposure group showed a significantly more conservative bias when judging facial expressions pain, meaning that they were less inclined to judge moderate pain expressions as painful compared to participants in the Control group. Event-related potential analyses in response to pain or neutral expressions indicated that this effect was related to a relative decrease in the central late positive potential responses to pain expressions. Furthermore, while the early N170 response was not influenced by repeated exposure to pain expressions, the P100 component showed an adaptation effect in the Control group only. These results suggest that repeated exposure to vicarious pain do not influence early event-related potential responses to pain expressions but decreases the late central positive potential. These results are discussed in terms of changes in the perceived saliency of pain expressions following repeated exposure.

Repeated exposure to others' pain reduces vicarious pain intensity estimation.

Pain perception in others can be influenced by different contextual factors. In clinical settings, the repeated exposure to others' pain has been proposed as a factor that could explain underestimation of patients' pain by health care providers. Previous research supported this idea by showing that repeated exposure to persons in pain biases the subsequent willingness to impute pain in others. However, it remains unclear if the effect of repeated exposure on the detection of pain extends to deliberate pain estimation of stimuli presented for a longer period. Therefore, in a first experiment, healthy participants were either exposed to clips of facial expressions of intense pain or neutral expressions before estimating the intensity of other individuals' pain expressions. To test the specificity of this effect with regard to the pain content, a second study was conducted with healthy adults, which compared the effect of exposure to fear, pain and neutral videos on subsequent pain assessment in others. Results from the first experiment indicated that repeated exposure to others' pain diminished the subsequent estimation of the intensity of pain in others. Results from the second experiment suggested that exposure to fear could bias pain estimation in a similar manner. However, the absence of difference in ratings between the exposure to fear and neutral groups warrants caution in the interpretation of these findings. By demonstrating that repeated exposure to others' pain diminished subsequent pain estimation in others, this study adds relevant information on the factors that could contribute to pain underestimation in health care professionals. WHAT DOES THIS STUDY ADD?: Repeated exposure to facial expressions of intense pain not only biases pain detection, but also pain estimation in others. Prior exposure to facial expressions of pain compared to exposure to neutral ones leads to a reduced estimation of others' pain. This effect is not specific to pain as exposure to another negative emotion (fear) also biases subsequent pain estimation. These results support the interpretation that the underestimation of patients' pain by health care professionals could be related to repeated exposure to other's pain.

Multiple faces of pain: effects of chronic pain on the brain regulation of facial expression.

Pain behaviors are shaped by social demands and learning processes, and chronic pain has been previously suggested to affect their meaning. In this study, we combined functional magnetic resonance imaging with in-scanner video recording during thermal pain stimulations and use multilevel mediation analyses to study the brain mediators of pain facial expressions and the perception of pain intensity (self-reports) in healthy individuals and patients with chronic back pain (CBP). Behavioral data showed that the relation between pain expression and pain report was disrupted in CBP. In both patients with CBP and healthy controls, brain activity varying on a trial-by-trial basis with pain facial expressions was mainly located in the primary motor cortex and completely dissociated from the pattern of brain activity varying with pain intensity ratings. Stronger activity was observed in CBP specifically during pain facial expressions in several nonmotor brain regions such as the medial prefrontal cortex, the precuneus, and the medial temporal lobe. In sharp contrast, no moderating effect of chronic pain was observed on brain activity associated with pain intensity ratings. Our results demonstrate that pain facial expressions and pain intensity ratings reflect different aspects of pain processing and support psychosocial models of pain suggesting that distinctive mechanisms are involved in the regulation of pain behaviors in chronic pain.

Clinically relevant behavioral endpoints in a recurrent nitroglycerin migraine model in rats.

BackgroundThis research sought to further validate the rat nitroglycerin (NTG) migraine model by comparing the effects of single versus recurrent NTG episodes on behavioral endpoints that mirror ICHD-3 diagnostic criteria for migraine, and to determine if the altered behavioral endpoints are reduced after administration of sumatriptan.MethodsSeparate cohorts of rats were administered NTG (10 mg/kg/2 ml) or saline (Experiment 1: single injection; Experiment 2: repeated injections; Experiment 3: repeated injections with sumatriptan [0.0, 0.3 and 1.0 mg/kg/ml] rescue. Behavioral endpoints were assessed 2 h after final NTG administration and included time in light/dark chambers for photophobia and activity, pain facial ratings, and cool (5 °C) and warm (46 °C) tail dip.ResultsThe first two experiments demonstrated that repeated (n = 5) but not single NTG injections produced photophobia, decreased activity, and yielded less weight gain than saline injections. Experiment 3 showed that sumatriptan attenuated hypoactivity, reduced facial expressions of pain, and reversed weight alterations in a dose-dependent manner.ConclusionsThese findings identify numerous clinical homologies of a recurrent NTG rat migraine model that may be useful for screening novel pharmacotherapies.