As part of our preparatory work packages, we are currently working on 8 experiments:
WP1.1.
With the aim of detecting the effects of several neurotransmitters in our other experiments, we are working to improve magnetic resonance spectroscopy (MRS). To this end we adopt numerous changes to the pulse sequences which are used in MRS. First steps towards an improvement of the signal to noise ratio (SNR) have been achieved.
WP1.3.
Units of the human cortex can be classified into separate specific layers. Detecting layer specific signals is usually done using magnetic resonance imaging (MRI) which can achieve a very high magnetic field during measurements, such as 7 Tesla. In this experiment we will compare the SNR from measurements using both 7 and 3 Tesla strength MRI. We have measured our paradigm with 7 Tesla strength. We are in the process of preparing the data collection on 3 Tesla.
WP1.4.
In order to detect changes in pain intensity as objectively as possible, we are developing a mobile device, which gives out a combined measure of psychophysiological signals, deliberately excluding subjective ratings given by our participants. At this point in time all necessary technical equipment and infrastructure has been installed. We have developed a deep learning analysis pipeline and are about to start the collection of pilot data.
WP2.1.
To investigate basal mechanisms of the hypothesis that expectations can induce selective attention towards signs of symptom improvement, we performed an experiment, where participants received sequences of slowly increasing (up-slopes) and sequences of slowly decreasing (down-slopes) pain-stimulation. The results of our analysis show that the pain-intensity was rated as lower during up-slopes when simultaneously performing a high attention task. Pain-intensity was also rated as lower during down-slopes, when simultaneously performing a low attention task. Skin conductance level tracked the up- and down-slopes and was modulated by the load of the cognitive task.
WP2.4.
Conditioned Pain Modulation (CPM) is a paradigm which is used to investigate how a painful stimulus can modulate the perceived pain from another painful stimulus. We performed an experiment in which our participants perceived pressure pain stimuli on both upper arms simultaneously, with a constant tonic conditioning pressure and a repeatedly occurring phasic test pressure. Pain ratings to the phasic test pain stimuli showed behavioral CPM developing over time. In the fMRI data we found effects of the paradigm in several brain regions, such as the right parietal operculum, posterior insula, as well as in bilateral primary somatosensory cortices.
WP2.5.
Generalization has been implicated as a core contributor to persistent pain, suggesting that imprecise encoding of an originally painful stimulus can lead to more generalization of subsequent pain. We are currently establishing a paradigm with which we will investigate the role of latent causes in pain perception. This can teach us about how encoding of painful stimuli might generalize to and influence the perception of new stimuli. In this paradigm participants will be trained to associate specific visual stimuli with low or high pain, resulting in two latent causes of pain. The degree of similarity between a new incoming stimulus and the previously learned causes will influence the perceived level of pain.
WP3.1.
In a further experiment we have tested whether pain relief is related to actual control or the perceived level of control. Since in most studies, controllability and predictability effects on pain processing are confounded we introduced a new experimental paradigm with the aim of disentangling these effects. During the experiment, which partly took place during fMRI, painful stimuli were either (1) controllable and predictable, (2) uncontrollable and predictable, or (3) uncontrollable and unpredictable. Participants rated individual heat pain stimuli applied to their forearm using a visual analogue scale. Our analyses indicate relevant pairwise interaction effects of controllability, predictability, and intensity on pain intensity ratings. Preliminary fMRI analyses suggest that there is an effect of controllability and predictability on attention and salience related brain network activation during expectation of painful stimuli and during the stimulation.
WP3.5.
As a preparation for potential exercise-induced analgesic effects in chronic pain we performed an experiment where aerobic exercise was performed outside of the scanner, followed by an fMRI session during which thermal and pressure pain was applied while placed in the scanner. Following each pain application, the participants rated the perceived intensity on a visual analog scale. Furthermore, pharmacological underpinnings in the opioid system of such an effect were investigated by the means of giving participants an individual dose of Naloxone, a medicine which reduces the effects of opioids. Our analyses of the collected data are ongoing.
