Tonic pain modulates neural correlates of associative phasic pain memories.

Tonic pain is proposed to maintain homeostatic integrity during recovery from injury. A key untested prediction of this homeostatic model is that it modulates internal representations of phasic pain. We investigated whether lateralised tonic pain modulates phasic pain-predictive cues on that side. Using a virtual-reality Pavlovian revaluation-style paradigm, we assessed physiological and neural conditioned responses with electroencephalography in theta, alpha, and beta frequency bands. Pain-predictive cues elicited neural enhanced alpha and beta suppression and increased pupil diameter during conditioning acquisition. Critically, tonic pain altered neural correlates of phasic conditioned responses during extinction, with reduced midfrontal theta synchronisation when the laterality of tonic pain was congruent with predicted phasic pain. These findings provide neural evidence for a topographically specific modulation of cue-pain representations by tonic pain, suggesting that tonic pain dynamically reshapes neural predictions of potential threat.