Altered prefrontal correlates of monetary anticipation and outcome in chronic pain

Abstract

Chronic pain may alter both affect- and value-related behaviors, which represents a potentially treatable aspect of chronic pain experience. Current understanding of how chronic pain influences the function of brain reward systems, however, is limited. Using a monetary incentive delay task and functional magnetic resonance imaging (fMRI), we measured neural correlates of reward anticipation and outcomes in female participants with the chronic pain condition of fibromyalgia (N = 17) and age-matched, pain-free, female controls (N = 15). We hypothesized that patients would demonstrate lower positive arousal, as well as altered reward anticipation and outcome activity within corticostriatal circuits implicated in reward processing. Patients demonstrated lower arousal ratings as compared with controls, but no group differences were observed for valence, positive arousal, or negative arousal ratings. Group fMRI analyses were conducted to determine predetermined region of interest, nucleus accumbens (NAcc) and medial prefrontal cortex (mPFC), responses to potential gains, potential losses, reward outcomes, and punishment outcomes. Compared with controls, patients demonstrated similar, although slightly reduced, NAcc activity during gain anticipation. Conversely, patients demonstrated dramatically reduced mPFC activity during gain anticipation-possibly related to lower estimated reward probabilities. Further, patients demonstrated normal mPFC activity to reward outcomes, but dramatically heightened mPFC activity to no-loss (nonpunishment) outcomes. In parallel to NAcc and mPFC responses, patients demonstrated slightly reduced activity during reward anticipation in other brain regions, which included the ventral tegmental area, anterior cingulate cortex, and anterior insular cortex. Together, these results implicate altered corticostriatal processing of monetary rewards in chronic pain.

Altered neural activity to monetary reward/loss processing in episodic migraine

“…It remains unclear however, whether the neural activation during reward consumption in migraine could be similar to the brain response found in different chronic pain syndromes. A recent study for example, detected different BOLD-responses to reward consumption between fibromyalgia (FM) patients and controls 33 . The authors found increased mPFC activity yielded for no loss outcomes compared to controls, which could indicate that FM patients tend to process no loss outcomes as a reward or relief rather than just a “zero sum” situation like healthy controls.…”

“…In addition, beyond the nature of rewards, it is worthwhile to investigate separately the neural responses during different stages of reward processing 32 . Although our understanding of the secondary reward anticipation and consumption in migraine is very limited, a recent study of fibromyalgia patients 33 found reduced medial prefrontal cortex (mPFC), ACC and VTA activity during gain anticipation, and heightened mPFC activity during non-punishment outcomes compared to controls. Based on these differences in corticostriatal processing during reward anticipation and consumption in chronic pain, we could hypothesize differences in migraine as well.…”

Pain, Touch, and Decision Making : Behavioral and Brain Responses to Affective Somatosensory Stimulation

“…In sum, the studies by Gandhi et al (2013) and Martucci et al (2018) both suggest altered reward processing during pain.…”

“…Taken together, Gandhi et al interpret these results as an increased motivation to obtain reward without accompanying increased pleasantness of the reward. On the other hand, a study comparing patients with the chronic pain condition fibromyalgia (n = 17) to a group of healthy controls (n = 15) found no difference in response times in the MID task (Martucci et al, 2018). Nevertheless, patients and controls differed in terms of brain activation during reward anticipation and outcome, measured using fMRI.…”

“…NAcc activation has previously been linked to anticipation of monetary rewards in the MID task (Knutson et al, 2001;Knutson et al, 2005;Miller et al, 2014; for a review, see Knutson & Greer, 2008) and mPFC activation has been linked to reward probability (Knutson et al, 2005) and reward outcome (Knutson et al, 2003). Thus, one of several possible interpretations of the results from Martucci et al (2018) is that the reduced anticipatory mPFC activity in chronic pain patients during gain anticipation reflects reduced reward probability estimates, although further research would be needed to confirm or dismiss this possibility. Furthermore, in response to a gain (vs. no gain) outcome, mPFC activity increased in both patients and controls, in line with previous findings (Knutson et al, 2003).…”