Pain, Touch, and Decision Making : Behavioral and Brain Responses to Affective Somatosensory Stimulation

Sammanfattning: Stimulation of sensory nerves can give rise to powerful affective experiences. Noxious stimuli can give rise to pain, an unpleasant experience which, in turn, causes suffering and constitutes a major societal burden. Touch, on the other hand, can feel pleasant and plays an important role in social relationships and well-being. Slow, gentle stroking of the skin in particular has been shown to activate C-tactile (CT) afferents, which are thought to signal affective and socially relevant aspects of touch. However, little is known about how pain and affective touch influence everyday decision making.In Paper I, we investigated the effect of acute physical pain on risk taking and intertemporal choice. Participants (n = 109) performed a series of economic decision-making tasks, once while experiencing acute thermal pain and once in a no-pain control condition. Results indicated that pain increased risk taking for monetary gains but not for equivalent losses, and increased impatience.In Paper II, we investigated the effect of affective touch on betrayal aversion, altruism, and risk taking. Participants (n = 120) performed a series of economic decision-making tasks, once while being stroked on the forearm at CT-optimal speed using a soft painter’s brush and once in a no-touch control condition. Results indicated no effect of affective touch on any of the outcome measures.In Paper III, we investigated how the ability to affect an upcoming painful event via voluntary action influences cortical processing of ongoing somatosensory stimulation. fMRI data was collected from 30 participants while they performed a task that involved pressing a response button to reduce the duration of upcoming thermal stimuli. Whole-brain analyses revealed no significant task-related effects in brain regions typically involved in pain, except activation in a cluster in anterior cingulate cortex (ACC) was greater when upcoming stimulation was painful than when it was nonpainful. However, region-of-interest analyses in anterior insula (AI) and midcingulate cortex (MCC) indicated that the noxious nature of the upcoming stimulation, as well as the ability to affect it, influenced processing of ongoing stimulation in both of these regions. Activation in MCC, but not AI, also correlated with response times.Taken together, these studies contribute to the broader understanding of everyday decision making, and of how affective experiences such as pain and touch shape everyday decisions and behaviors.