The relevance of accounting for parasympathetic as well as sympathetic arousal in threat conditioning: Methodological and clinical considerations

Alterations in associative threat learning have been thought to underlie the aetiology and maintenance of anxiety disorders. Recent insights into the facilitatory role of parasympathetic arousal for threat coping have raised the question whether individual differences in sympathetic versus parasympathetic dominance during threat learning may shed light on the complex relationship with anxiety vulnerability versus resilience. We applied an established differential-cue delay threat conditioning paradigm in 78 neurotypical individuals and assessed parasympathetic responses (threat-induced bradycardia), as well as sympathetic responses (threat-induced tachycardia and increased skin conductance responses-SCR). We found evidence that patterns of threat-induced bradycardia as well as tachycardia are present during associative learning. Threat bradycardia was linked to weaker initial conditioned SCRs (mainly driven by responses to the CS+), a finding that may be relevant for current common practice in the field of threat learning: namely participants with weak differential skin conductance responses - who according to frequently applied 'SCR non-learner' criteria are often considered non-learners and sometimes even excluded from analyses - were in fact showing successful learning in terms of parasympathetic arousal. Additionally, the presence of threat bradycardia as well as the magnitude of overall conditioned heart rate responses were linked to relatively lower trait anxiety. These findings not only have practical research implications but also clinical implications when assessing markers for anxiety vulnerability versus resilience.