ERP Indicators of Self-Pain and Other Pain Reductions due to Placebo Analgesia Responding: The Moderating Role of the Fight-Flight-Freeze System

Abstract

This study evaluates the modulation of phasic pain and empathy for pain induced by placebo analgesia during pain and empathy for pain tasks. Because pain can be conceptualized as a dangerous stimulus that generates avoidance, we evaluated how approach and avoidance personality traits modulate pain and empathy for pain responses. We induced placebo analgesia to test whether this also reduces self-pain and other pain. Amplitude measures of the N1, P2, and P3 ERPs components, elicited by electric stimulations, were obtained during a painful control, as well as during a placebo treatment expected to induce placebo analgesia. The placebo treatment produced a reduction in pain and unpleasantness perceived, whereas we observed a decrease in the empathy unpleasantness alone during the empathy pain condition. The moderator effects of the fight-flight-freeze system (FFFS) in the relationships linking P2 and P3 amplitude changes with pain reduction were both significant among low to moderate FFFS values. These observations are consistent with the idea that lower FFFS (active avoidance) scores can predict placebo-induced pain reduction. Finally, in line with the revised Reinforcement Sensitivity Theory (r-RST), we can assume that phasic pain is an aversive stimulus activating the active-avoidance behavior to bring the system back to homeostasis.

Placebo Analgesia Changes on Self-Pain and Empathy for Pain: Influences of Event-Related EEG Oscillations, Heart Rate Variability, and Personality

“…Later these authors showed that informing in advance participants that they would receive electric shocks increased their pain-related fear that reduced the PA effect 22 . In line with these ndings, we have recently observed smaller reductions in pain ratings and smaller decreases in the P2 and P3 amplitudes of the ERP elicited by electric stimuli in higher fear-related trait scorers 23 .…”

“…These are new ndings, considering that the available research evidence does not yet allow more precise assignment of the different components to the various modulations of pain (see Ploner et al's review 69 ). Additionally, the present PA empathy ndings seem to be compatible with previous ndings showing that the observation of other's pain increased activation in the sensorimotor cortex, as expressed by increased central β(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)…”

“…In contrast, in a later study, Riečanský and colleagues 12 found increased motor readiness and activation in the sensorimotor cortex, as expressed by increased central β (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and mu (7)(8)(9)(10)(11)(12) desynchronization when participants saw videos depicting painful needle injections than non-painful control conditions. Indeed, they later observed that the activation of the sensorimotor cortex became more robust with increasing illusory ownership of the observed hand 13 .…”

“…To investigate pain-related empathy, we bene t from a known paradigm developed by Singer and colleagues 36 . Rutgen et al 33 and ourselves 23 employed this paradigm to test empathic experience wherein the object of empathy experience was a real person seated on the left side of the participant chair (see Fig. 1).…”

“…Before EEG recordings, each participant underwent a psychophysical pain calibration procedure to determine sensory and pain thresholds making possible a reliable electrical stimulation intensity for painful and no painful stimuli. Details are provided in 23 and in the Supplementary Information, section S2. After the calibration procedure, participants were exposed to two experimental testings: a control pain condition and a PA treatment.…”