Brain and pain: old assumptions and new science about chronic pain

The authors summarise the evolving understanding of the neuropsychophysiology of chronic pain, including the relevance of adverse childhood experiences in facilitating it and similarities between the central physiology of chronic pain and opioid addiction. Emerging understanding highlights the importance of dopamine-expressing GABAergic neurons in the nucleus accumbens and suggests that D-1 expression is associated with a sense of pleasure and approach behaviour and D-2 with a sense of punishment and behavioural inhibition. Regulation of D-1 and D-2 expression may be mediated by nigrostriatal and medial frontal striatal pathways within the increasingly understood brain as a 'predictive' organ. The distinction between the predictive brain and personal 'expectations' and the importance of the latter for clinical outcomes are emphasised. The relevance of findings for possible future psychopharmacological treatment avenues is also presented.