Abstract
Pain demands attention, yet pain can be reduced by focusing attention elsewhere. The neural processes involved in this robust psychophysical phenomenon, attentional analgesia, are still being defined. Our previous fMRI study linked activity in the brainstem triad of locus coeruleus (LC), rostral ventromedial medulla (RVM) and periaqueductal grey (PAG) with attentional analgesia. Here we identify and model the functional interactions between these regions and the cortex in healthy human subjects (n = 57), who received painful thermal stimuli whilst simultaneously performing a visual attention task. RVM activity encoded pain intensity while contralateral LC activity correlated with attentional analgesia. Psycho-Physiological Interaction analysis and Dynamic Causal Modelling identified two parallel paths between forebrain and brainstem. These connections are modulated by attentional demand: a bidirectional anterior cingulate cortex (ACC) – right-LC loop, and a top-down influence of task on ACC-PAG-RVM. By recruiting discrete brainstem circuits, the ACC is able to modulate nociceptive input to reduce pain in situations of conflicting attentional demand.
Highlights
Attentional analgesia is a well-characterised phenomenon whereby increased cognitive load can decrease pain perception (Peyron et al, 2000; Bantick et al, 2002; Brooks et al, 2002; Valet et al, 2004; Brooks et al, 2017; Sprenger et al, 2012)
Central to attentional analgesia is the concept of divided attention, whereby less cognitive resource is available to be allocated to nociception and pain
In this study we have been able to resolve parallel cortical – brainstem pathways that form a network that is functionally engaged when pain perception is attenuated during attentional analgesia
Summary
Attentional analgesia is a well-characterised phenomenon whereby increased cognitive load can decrease pain perception (Peyron et al, 2000; Bantick et al, 2002; Brooks et al, 2002; Valet et al, 2004; Brooks et al, 2017; Sprenger et al, 2012). This can be achieved by diverting attention from a painful stimulus to a visual task or by active mind-wandering (Bushnell et al, 2013; Kucyi et al, 2013). The processes regulating attentional focus is of importance in the development, maintenance and potentially resolution of chronic pain states
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