Comments after 30 years of the gate control theory

[Control center team in interdisciplinary multimodal pain therapy]

The topic of this article is the team in interdisciplinary multimodal pain therapy (IMPT) in the context of the development of the team concept. The starting points are historical developments, both social and scientific. After World War II numerous war victims continued to suffer from persistent pain. On the part of medicine, the consequences were the failure of the usual procedures for acute pain and the resulting helplessness. Both the concept of pain as a symptom of physical injury and also the previous treatment options were no longer adequate. Very early on an interdisciplinary approach to pain management was organized. This involved the communication of experts from various disciplines with very different competencies and opinions. Various medical disciplines and psychotherapy were the core subjects. Crucial for functioning teams is an effective cooperation and interaction. Related organizational issues, conflicts, peculiarities, and possibilities for solutions are presented. In the meantime, IMPT as a procedure has become a regular service provided in health care.

Pain modulation in the spinal cord

The sensory inflow from the periphery that triggers innocuous and painful sensations is highly complex, capturing key elements of the nature of any stimulus, its location, intensity, and duration, and converting this to dynamic action potential firing across a wide population of afferents. While sensory afferents are highly specialized to detect these features, their input to the spinal cord also triggers active processing and modulation there which determines its output, to drive the sensory percept experienced and behavioral responses. Focus on such active spinal modulation was arguably first introduced by Melzack and Wall in their Spinal Cord Gate Control theory. This theory has had a profound influence on our understanding of pain, and especially its processing, as well as leading directly to the development of clinical interventions, and its historical importance certainly needs to be fully recognized. However, the enormous progress we are making in the understanding of the function of the somatosensory system, means that it is time to incorporate these newly discovered features into a more complex and accurate model of spinal sensory modulation.

Touch and social support influence interpersonal synchrony and pain

Interpersonal touch and social support can influence physical health, mental well-being and pain. However, the mechanisms by which supportive touch promotes analgesia are not well understood. In Study 1, we tested how three kinds of social support from a romantic partner (passive presence, gentle stroking and handholding) affect pain ratings and skin conductance responses (SCRs). Overall, support reduced pain ratings in women, but not men, relative to baseline. Support decreased pain-related SCRs in both women and men. Though there were no significant differences across the three support conditions, effects were largest during handholding. Handholding also reduced SCRs in the supportive partner. Additionally, synchronicity in couples’ SCR was correlated with reductions in self-reported pain, and individual differences in synchrony were correlated with the partner’s trait empathy. In Study 2, we re-analyzed an existing dataset to explore fMRI activity related to individual differences in handholding analgesia effects in women. Increased activity in a distributed set of brain regions, including valuation-encoding frontostriatal areas, was correlated with lower pain ratings. These results may suggest that social support can reduce pain by changing the value of nociceptive signals. This reduction may be moderated by interpersonal synchrony and relationship dynamics.

Pain relief by touch: a quantitative approach

Pain relief by touch has been studied for decades in pain neuroscience. Human perceptual studies revealed analgesic effects of segmental tactile stimulation, as compared to extrasegmental touch. However, the spatial organisation of touch–pain interactions within a single human dermatome has not been investigated yet. In 2 experiments we tested whether, how, and where within a dermatome touch modulates the perception of laser-evoked pain. We measured pain perception using intensity ratings, qualitative descriptors, and signal detection measures of sensitivity and response bias. Touch concurrent with laser pulses produced a significant analgesia, and reduced the sensitivity in detecting the energy of laser stimulation, implying a functional loss of information within the ascending Aδ pathway. Touch also produced a bias to judge laser stimuli as less painful. This bias decreased linearly when the distance between the laser and tactile stimuli increased. Thus, our study provides evidence for a spatial organisation of intrasegmental touch–pain interactions.

The cognitive modulation of pain: hypnosis- and placebo-induced analgesia

Nowadays, there is compelling evidence that there is a poor relationship between the incoming sensory input and the resulting pain sensation. Signals coming from the peripheral nervous system undergo a complex modulation by cognitive, affective, and motivational processes when they enter the central nervous system. Placebo- and hypnosis-induced analgesia form two extreme examples of how cognitive processes may influence the pain sensation. With the advent of modern brain imaging techniques, researchers have started to disentangle the brain mechanisms involved in these forms of cognitive modulation of pain. These studies have shown that the prefrontal and anterior cingulate cortices form important structures in a descending pathway that modulates incoming sensory input, likely via activation of the endogenous pain modulatory structures in the midbrain periaqueductal gray. Although little is known about the receptor systems involved in hypnosis-induced analgesia, studies of the placebo response suggest that the opiodergic and dopaminergic systems play an important role in the mediation of the placebo response.

Environmental and behavioral strategies to prevent and manage neonatal pain

This article provides an overview of environmental and behavioral methods for pain management in newborn infants. Specific interventions in the areas of containing, positioning, nonpainful sensory stimuli, non-nutritive sucking, sucrose, and procedural technique are discussed. The conceptual framework and research evidence for the efficacy of these methods are examined. Opportunities for further research to evaluate the comparative efficacy of environmental and behavioral pain interventions are emphasized.

Non-nociceptive aspects of persistent musculoskeletal pain

Persistent pain is often difficult to understand and to treat. Clinical and neurophysiological evidence is offered, suggesting that this often occurs because persistent pain is partially or wholly of non-nociceptive afferent origin. The concept of non-nociceptive pain and the potential roles of proprioceptive afferents in the production of non-nociceptive pain are particularly emphasized. It is suggested that non-nociceptive pain is often an important component of pain associated with peripheral and central neuropathy, fibromyalgia, trauma-induced pain, idiopathic low back pain, and chronic regional pain syndrome. Non-nociceptive pain is often dependent upon central sensitization induced by prior or ongoing nociception. Therapeutic methods which minimize nociceptive afferent activity are important in the prevention and/or elimination of often intractable non-nociceptive pain.