Sustained perturbation in functional connectivity induced by cold pain
Functional connectivity (FC) perturbations have been reported in multiple chronic pain phenotypes, but the nature of reported changes is varied and inconsistent between cohorts. Increases and decreases in connectivity strength in task negative and positive networks, for example, the default mode and salience networks (DMN/SN), respectively, have been described, but how other networks are effected, for example, descending pain control networks, remains unknown. Whether connectivity changes relate to peripherally-mediated nociceptive afferent input, represent coping strategies or are sequelae of chronic pain, e.g. anxiety/depression, is also unknown. Here, we examined FC changes in response to experimentally-administered tonic cold pain in healthy volunteers as a means of disambiguating the nature of connectivity changes. We assessed FC prior to, during, and following tonic cold painful stimulation in four seed regions: ventromedial prefrontal cortex (vmPFC), rostral anterior insula (rAI), subgenual anterior cingulate cortex (ACC) and periaqueductal grey (PAG) and recorded subjectively reported pain using a computerised visual analogue scale. We saw DMN FC changes during painful stimulation and that inter-network communication between the rAI and sgACC seeds with the vmPFC became less anti-correlated during pain, whereas PAG-precuneus FC decreased. Pain-induced FC alterations largely persisted during a 6-minute recovery period following cessation of the painful stimulus. Observed FC changes related to the magnitude of individuals subjectively reported pain. We provide new insights into FC changes during and following tonic cold-pain and suggest that some FC changes observed in chronic pain patients may relate to the presence of an ongoing afferent peripheral drive.