Vagally Mediated Heart Rate Variability Promotes the Perception of Paradoxical Pain

Self-regulation mechanisms are governed by prefrontal inhibitory processes and play a crucial role in the modulation of pain. In the present study the thermal grill paradigm was used to investigate the association of vagally mediated resting heart rate variability, a psychophysiological marker of trait self-regulatory capacity, with paradoxical pain sensations induced by non-noxious stimulation. This thermal grill illusion is only perceived by part of the tested individuals. The mechanisms underlying the observed interindividual differences in paradoxical pain sensitivity are largely unknown. During the experimental task, a temperature combination of 15 °C and 41 °C was set at the glass tubes of the thermal grill. The 52 healthy participants placed their dominant hand on the grill for a duration of one min. The magnitude of sensory and affective pain sensations perceived during stimulation was assessed with numerical rating scales. Before stimulation, a short-term electrocardiogram was recorded to compute vagally mediated heart rate variability at rest. Logistic regression analyses revealed that participants with higher vagal tone were significantly more likely to perceive the thermal grill illusion than subjects displaying lower resting heart rate variability. Paradoxical pain sensations were primarily predicted by normalized respiratory sinus arrhythmia. Our results confirm that the magnitude of vagally mediated resting heart rate variability is associated with the individual disposition to illusive pain perceptions. Since the latter is considered to be a marker of trait self-regulation ability, the present findings may corroborate and complement previous evidence for an impact of psychological characteristics on paradoxical pain sensitivity.