Personality differences affect brainstem autonomic responses to visceral pain

Brainstem autonomic nuclei integrate inter-oceptive inputs including pain, with descending mod-ulation, to produce homeostatic and defence outputs.Cardiac Vagal Control is especially implicated in psy-chophysiological processes for both health and diseaseand is indexed non-invasively by heart rate variability.The study aim was to determine the nature of psycho-physiological response profiles for visceral pain. Nine-teen healthy subjects had electrocardiographicrecordings at rest and during 10 painful oesophagealballoon distensions. Cardiac Vagal Control originatingfrom nucleus ambiguus (CVCNA) was determined bypolynomial filter application to the electrocardiograminter-beat interval series. Heart rate andÔCardiacSympathetic Index (CSI)Õwere also determined. Psy-chological state and trait, including neuroticism andextroversion, were assessed. Subjects who increasedCVCNAto pain were more neurotic, anxious and sen-sory sensitive than those who decreased CVCNA.Clus-ter analysis identified two psychophysiological groups:Group 1 (n = 11) demonstrated lower baseline CVCNA(P = 0.0001), higher heart rate (P = 0.02) andCSI (P = 0.015), pain tolerance at lower balloon vol-umes (P = 0.04), but attenuated heart rate response topain (P = 0.01). Group 2 (n = 8) had the converse profile.Neuroticism scores were higher (P = 0.0004) andextroversion lower (P = 0.01) for group 1 than group 2.Two distinct psychophysiological response profiles tovisceral pain exist that are influenced by personality.These may reflect different psychobiological bases foractive and passive defence repertoires. Prevalence andclinical relevance of these endophenotypes as vulnera-bility factors for pain and emotion disorders warrantfurther exploration.