Max Planck Research Group Pain Perception

In its acute form, pain is a beneficial signal that is warning us about impending or actual tissue damage. In its chronic form however, pain is a source of immense suffering for millions of people. At the same time, the perception of pain does not exhibit a one-to-one relationship with tissue damage, i.e. there are situations where we might not perceive much pain despite having sustained a strong injury (and vice versa). This flexibility suggests a strong involvement of the central nervous system in the perception of pain and our group's focus is to investigate the neural ‘building blocks’ of this multi-faceted pain experience. For this endeavour, we use behavioural recordings in combination with advanced neuroimaging techniques at all level of the central nervous system, focussing especially on the human spinal cord, which is the first station of central nervous system pain processing and also critically involved in pathological forms of pain. Our main research areas currently are:

(1) Cognitive modulation of pain

Pain is substantially influenced by a wide range of contextual factors. The primary focus of our research lies on the mechanisms underlying this contextual modulation of pain perception, with particular emphasis on cognitive factors such as expectations. To investigate these processes, we employ a combination of psychophysical and psychophysiological as well as EEG and fMRI approaches. Theoretically, our research is embedded in a contemporary perspective that conceptualizes perception not as a passive response to sensory stimuli, but as an active process. Within this framework, the central nervous system continuously generates predictions about incoming sensory signals and updates these predictions in light of new sensory information. In this context, we address questions such as: How do prior experiences shape current pain perception? Is it possible to selectively enhance specific predictive signals in order to optimize pain relief?

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(2) Pain-related learning and memory

Pain is a highly effective teaching signal, as demonstrated in a wide range of aversive conditioning paradigms. Accordingly, another focus of our research is the investigation of factors that determine the acquisition, maintenance, and updating of pain-related associations and predictions. Current studies address questions such as: What is the specific informational content of pain-related predictive signals? Which mechanisms underlie pain-related extinction learning, and at which levels are these implemented?

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(3) Characterising fundamental processes underlying thermoception

Recent studies in mice have demonstrated that the neuronal coding principles of temperature differ fundamentally between the cold and warm ranges. Understanding the mechanisms underlying human temperature perception is of central importance, particularly in light of increasingly frequent temperature extremes. Using a combination of model-based psychophysical and neuroimaging (fMRI & EEG) approaches, we investigate the coding principles that underlie human temperature perception. Current studies, for example, address questions such as: Is the response of the human autonomic nervous system also based on differential coding for cold and warm stimuli, and how does this relate to subjectively reported sensations? Do the coding principles for cold and warm stimuli differ in the painful versus non-painful range at the earliest stage of processing in the spinal cord?

(4) Multiple levels of somatosensory and nociceptive processing: from peripheral signals to perception

Between the arrival of a stimulus and the emergence of a percept lies a multitude of processing steps. We are working on establishing approaches that allow for simultaneous insights into all of these stages of somatosensory and nociceptive processing – essentially tracing the pathway from receptor to perception. This is indispensable not only for a comprehensive characterization of bottom-up processes, but especially for understanding their interaction with top-down factors such as expectation or attention, as these exert their influence at multiple levels and thereby shape the complexity of pain perception.

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(5) Methods development

Experimental pain research faces the challenge that, due to ethical and safety considerations, only a relatively limited number of nociceptive stimuli can be administered. Given the consequently low signal-to-noise ratio, this necessitates the use of highly sensitive data acquisition and analysis methods, the development of which we are continuously advancing. In this context, we examine, for example, the reliability of different measurement approaches, develop novel analytical strategies, and establish standardized measurement protocols within multicentre initiatives.

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