Representation of Spatial Information in Key Areas of the Descending Pain Modulatory System

Abstract

Behavioral studies have demonstrated that descending pain modulation can be spatially specific, as is evident in placebo analgesia, which can be limited to the location at which pain relief is expected. This suggests that higher-order cortical structures of the descending pain modulatory system carry spatial information about the site of stimulation. Here, we used functional magnetic resonance imaging and multivariate pattern analysis in 15 healthy human volunteers to test whether spatial information of painful stimuli is represented in areas of the descending pain modulatory system. We show that the site of nociceptive stimulation (arm or leg) can be successfully decoded from local patterns of brain activity during the anticipation and receipt of painful stimulation in the rostral anterior cingulate cortex, the dorsolateral prefrontal cortices, and the contralateral parietal operculum. These results demonstrate that information regarding the site of nociceptive stimulation is represented in these brain regions. Attempts to predict arm and leg stimulation from the periaqueductal gray, control regions (e.g., white matter) or the control time interval in the intertrial phase did not allow for classifications above chance level. This finding represents an important conceptual advance in the understanding of endogenous pain control mechanisms by bridging the gap between previous behavioral and neuroimaging studies, suggesting a spatial specificity of endogenous pain control.

Psychophysical and neurophysiological responses to acupuncture stimulation to incorporated rubber hand

“…It is thought that the activations of the DLPFC, insula, and SII were associated with the physiological responses evoked by acupuncture stimulation to the incorporated hand, but only when the participants perceived the rubber hand to be their own. The DLPFC is a key component of the descending pain modulatory system that is associated with the generation, maintenance, and manipulation of cognitive representations, which is consistent with the role it plays in expectations [17,24]. Brain activation in the DLPFC may be derived from the expectations experienced by the participant during acupuncture treatment, particularly because of the visual components inherent in the design of the current study.…”

Modulation of pain, nociception, and analgesia by the brain reward center

“…Recent work also reveals alterations in connectivity between the mPFC and the hippocampus in patients suffering from burning mouth syndrome (Khan et al, 2014), and alterations in dorsolateral PFC activity in anticipation or reception of a painful stimulus (Ritter et al, 2014). Such data not only demonstrate that chronic pain conditions elicit changes in neuronal activity, but they also link pain threshold to the circuitry between the ventral tegmental area/substantia nigra and NAc.…”

Placebo Responses on Cardiovascular, Gastrointestinal, and Respiratory Organ Functions

“…These site-specific responses were blocked by the opiate antagonist naloxone, suggesting a somatotopic activation of the endogenous opioid pathways (Benedetti et al 1999b). Indeed, a recent brain imaging study demonstrated site-specific activation of the descending pain-modulatory system during pain stimulation at different body sites (Ritter et al 2014). It would be challenging to likewise compare the neurobiological pathways of placebo interventions targeting different autonomic organs, such as the heart and the stomach.…”