Background: Chronic pain and mood disorders share common neuroanatomical substrates involving disruption of the reward system. Although increase in negative affect (NA) and decrease in positive affect (PA) are well-known factors complicating the clinical presentation of chronic pain patients, our understanding of the mechanisms underlying the interaction between pain and PA/NA remains limited. Here, we used a validated task probing behavioral and neural responses to monetary rewards and losses in conjunction with functional magnetic resonance imaging (fMRI) to test the hypothesis that dysfunction of the striatum, a key mesolimbic structure involved in the encoding of motivational salience, relates to mood alterations comorbid with chronic pain. Methods: Twenty-eight chronic musculoskeletal pain patients (chronic low back pain, n=15; fibromyalgia, n=13) and 18 healthy controls underwent fMRI while performing the Monetary Incentive Delay (MID) task. Behavioral and neural responses were compared across groups and correlated against measures of depression (Beck Depression Inventory) and hedonic capacity (Snaith-Hamilton Pleasure Scale). Results: Compared to controls, patients demonstrated higher anhedonia and depression scores, and a dampening of striatal activation and incentive-related behavioral facilitation (reduction in reaction times) during reward and loss trials of the MID task (ps < 0.05). In all participants, lower activation of the right striatum during reward trials was correlated with lower incentive-related behavioral facilitation and higher anhedonia scores (ps < 0.05). Finally, among patients, lower bilateral striatal activation during loss trials was correlated with higher depression scores (ps < 0.05). Conclusions: In chronic pain, PA reduction and NA increase are accompanied by striatal hypofunction as measured by the MID task.
Bibliographical noteFunding Information:
This research was supported by grants from the National Institute of Health (NIH) R01 NS094306-01A1 (MLL), R01 NS095937-01A1 (MLL), R21 NS087472-01A1 (MLL), and Department of Defense W81XWH-14-1-0543 (MLL) and an Early Career Award from IASP (MLL). VN was supported by grants from the Office of the Director ( OT2-OD023867 ), P01 AT009965 , R61 AT009306 , R33 AT009306 , R01 AT007550 , and R01 AR064367 . DAP was partially supported by National Institute of Health (NIH) R37 MH095809 and R01 MH101521 .
- Chronic pain
- Functional magnetic resonance imaging (fMRI)
- Monetary incentive delay task
- Mood alteration
- Reward circuitry
- Striatal hypofunction
ASJC Scopus subject areas
- Cognitive Neuroscience