Projects

Although there has been much progress in the understanding of phantom limb pain (PLP), we still do not know which factors are antecedents and which are consequences of the pain and how central, peripheral and psychological factors interact. This project seeks to determine the development of phantom limb pain in a longitudinal fashion and will examine how central and peripheral changes as well as psychological factors develop over time. In addition, the role of central nervous system excitability and plasticity and the influence of use-dependent plasticity and body perception will be examined. Further, we will examine how evoked phantom pain is represented in the brain. Finally, we will employ high field imaging, neurofeedback using real time functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) to identify causal circuits for phantom pain.

Brain circuits involved in pain processing and body representation are closely connected and interact more than previously thought. Somatosensory, visual, interoceptive and motor processes contribute to the formation of body perception and can be combined in treatments designed to reestablish normal body representation. Based on the development of novel psychological interventions targeting body representation in phantom limb pain, we devise new virtual and augmented reality-based training pro-cedures to reestablish normal body representation and improve sensory, motor and cognitive function. We apply these interventions in post-injury pain and motor dysfunction, where the counteracting of long-term immobility by feedback of movement should shorten recovery times and preserve muscle function. Another novel application is in chronic musculoskeletal pain, where the systematic shaping of intact body representation including interoception, should reduce pain and pain behaviors and alter maladaptive brain circuits. We expand this approach to early dementia, where the breakdown of sen-sorimotor processing and immobility may be important in disease progression. We employ novel im-plicit and explicit assessment methods of these perceptual and neuronal changes involving psycho-physics, computational modeling, physiological recordings and brain imaging methods. These studies are the basis for mechanistic treatment approaches and also advance basic research on body repre-sentation and multisensory integration.

Schmerzlinderung als Belohnung, d.h. als Verhaltenskonsequenz, tritt nahezu alltäglich auf, z.B. durch eine Änderung der Körperposition bei Rückenschmerzen. Für Schmerzpatienten ist solche Schmerzlinderung von besonderer Bedeutung, die aber paradoxerweise zur Steigerung der Schmerzsensitivität führen können. Trotzdem wurde belohnende Schmerzlinderung bisher kaum untersucht und zugrunde liegenden neurophysiologischen Mechanismen in Gesunden und Schmerzpatienten sind unklar. Das Projekt soll daher (1) Effekte von Schmerzlinderung als Belohnung auf Wahrnehmung und Lernen in Gesunden und chronischen Schmerzpatienten charakterisieren, (2) die Rolle der Neurotransmitter Dopamin und endogender Opioide dabei und (3) funktionelle und strukturelle neurale Korrelate dieser Effekte bestimmen. In zwei Studien spielen die Probanden ein Glücksrad, dass Schmerzlinderung als Belohnung operationalisiert. Beide Studien tragen zur Charakterisierung belohnender Schmerzlinderung bei. In Studie 1 werden außerdem die Rolle von Dopamin und endogenen Opioiden in Gesunden untersucht; neurale Korrelate in Gesunden und Schmerzpatienten in Studie 2. Wichtige Erkenntnisse zu den Mechanismen eines alltäglichen und relevanten Prozesses werden erwartet, die für die Grundlagen- wie auch Klinische Forschung von Bedeutung sind.