Neuronal coding of tonic pain

• Applicant: Privatdozent Enrico Schulz, Ph.D.
• Subject Area: Human Cognitive and Systems Neuroscience
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 236186819

A steady and continuously incoming stream of sensory information is a major characteristic of our daily human life experience. Within the stream, many sensations - like hearing speech, reading a newspaper or having a headache - are perceived as variably intense and important. Research on prolonged and continuously changing stimuli is vastly under-represented in the literature in spite of the ecologic validity of this approach. Here, we propose an investigation in which we aim at identifying those neuronal processes that reflect the perception of the fluctuating pain intensity in response to prolonged (tonic) painful heat stimulation. During the recording of fMRI data we will adapt the applied heat pain (thermode temperature) continuously and automatically with means of an electronic control device. This approach enables to keep the perception (subjective pain rating) at a predefined intensity level. The study design exceeds conventional event-related studies in terms of ecological validity. The preliminary data suggest different phenomena in the brain which may involve complementary aspects during the processing of pain: pain rating reflects the subjective percept; a decay of temperature over time reflects sensitisation of the subjects.The proposed project is aiming at exploring those brain areas that signal the perceived intensity of tonic pain, which we believe is - to a certain extent - decoupled from applied stimulus characteristics. This rather cognitive rating process is suggested to involve other brain areas than those coding for the heat of the thermode. The continuous adaptation of applied thermode temperature will keep the perception at a predefined level. It thus controls for cortical (habituation/sensitisation) and peripheral (adaptation of peripheral nerves) processes that would otherwise lead to unbearable pain or no pain at all. It remains to be elucidated whether previous findings about prefrontal, insular, and cingulate contribution to the coding of brief phasic pain perception (pain intensity) also applies to tonic pain coding. Ongoing, continuous pain that is fluctuating in its intensity is characteristic of many clinical conditions of prolonged acute and chronic pain and therefore should be the standard for pain research, especially in patient populations. The proposed project thus allows to track the time courses of an individual's pain perception as well as sensitisation/habituation due to prolonged pain exposure. The processes coding for objective aspects (applied thermode temperature) will be separated from subjective aspects (individual pain rating) of pain perception.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professorin Dr. Irene Tracey