Pain processing

Fig. 1. Cortical areas that receive information from the spinothalamic tract. Main spinothalamic and thalamocortical projections were summarized and simplified from several reports on the central nociceptive pathways in the monkey (Vogt et al., 1979; Willis, 1985; Apkarian and Shi, 1994; Craig, 1996). Cortico-cortical connections are not shown. ACC, anterior cingu- late cortex; CL, centrolateral nucleus; MDvc, ventrocaudal part of medial dorsal nucleus; Pf, parafascicular nucleus, SI, primary somatosensory cor- tex; SII, secondary somatosensory cortex; VMpo, posterior part of ventro- medial nucleus; VPI, ventral posterior inferior nucleus; VPL, ventral posterior lateral nucleus; VPM, ventral posterior medial nucleus. 

In summary, we propose that the activity of the cortical areas classically observed in response to nociceptive stimuli constitutes a network involved in detecting salient sensory events in order to prioritize their access to attentional and executive functions. Through biasing operations, the main function of the proposed salience detection system would be thus to facilitate the processing of behaviorally significant (e.g., potentially threatening) sensory input and to select the appropriate response, regardless of whether this input is conveyed through nociceptive pathways. This view does not imply that the cortical processing underlying the salience detection system does not contribute to the experience of pain. On the contrary, it highlights the fact that such a system subtends one of the most important functions of the nociceptive system, namely the ability to detect salient changes and, possibly, to integrate them into a peripersonal representation of our body. In order words, the salience detection system would represent a network by which we react to a wasp when viewing the wasp approaching the hand, but even before being stung by it.

medial and lateral pathways

Saliency detection system conclusion