The burn that wasn’t there: Illusions in the thermo-nociceptive system
What does it mean to experience an illusion of pain? The typical role of pain is to signal when the body is damaged. However, pain illusions in the absence of any risk of tissue damage are common in the normal population. For example, alternating innocuous cold and warm stimuli on the skin produces unique and paradoxical sensations of heat and pain, often referred to as the thermal grill illusion. The perception of pain from combinations of cold and warm stimuli that are felt as painless in isolation is at first-glance counter-intuitive. But as in other sensory domains, this edge case reveals complex sensory integration mechanisms operating in the human central nervous system. In this research, our core questions concern the functional properties, clinical relevance, as well as brain and spinal cord basis of illusory pain. We will be working on these questions for the next 5 years, thanks to support from a European Research Council Starting Grant.
Where do you feel it? Mechanisms of pain and touch localization
Having conscious and automatic access to bodily signals such as pain is lifesaver. Knowing where pain is located guides appropriate and protective actions and can be easily communicated to others. “Where does it hurt?” is often the first question we ask to a person in pain. Pain localization is usually intuitive and informative, as the sensations are localized in correspondence of the tissue damage or inflammation. However, in several chronic pain conditions, pain is mislocalized to a body area that is undamaged or missing. For example, the disrupted correspondence between tissue damage and pain localization is a key feature of post-amputation pain, where sensations are referred to a missing limb. In our lab, we investigate the neural mechanisms underlying the localization or mislocalization of painless and painful sensations on the skin. We focus on the understanding of the complex organisation and interactions of peripheral, spinal and brain mechanisms supporting our ability to attribute the origin of tactile, thermal and painful sensations to specific locations on the body.
To answer our research questions, we combine psychophysics and behavioural paradigms which non-invasive neuroimaging techniques. Our favourite tool is magnetoencephalography (MEG) and we have been recently experimenting with optically pumped magnetometers (OPMs), together with Sarang Dalal. We also enjoy working with electroencephalography (EEG), as well as structural and functional MRI of the brain and spinal cord.