Sensory Evidence and Expectations in Pain Processing
Condition: Experimental Pain in Healthy Human Participants
Study type: Interventional

Summary: 
      Pain is a highly complex and subjective phenomenon which is not only rooted in sensory
      information but also shaped by cognitive processes such as expectation. However, the
      interaction of brain activity cording sensory information and expectation in pain processing
      are not completely understood. Predictive coding models postulate specific hypothesis about
      the interplay between bottom-up sensory information and top-down expectations in terms of
      prediction errors and predictions, respectively. They further implicate brain oscillations at
      different frequencies, which play a crucial role in processing prediction errors and
      predictions. More specifically, recent evidence in visual and auditory modalities suggests
      that predictions are reflected by alpha (8-13 Hz) and beta oscillations (14-30 Hz) and
      prediction errors by gamma oscillations (60-100 Hz). However, for the processing of pain,
      these frequency-specific relationships have not been addressed so far. The current project
      aims to investigate brain activity which reflects predictions, prediction errors and sensory
      evidence in pain processing using a cueing paradigm. To this end, we will apply painful
      stimuli with low and high intensity to the dorsum of the left hand in 50 healthy subjects. A
      visual cue, preceding to each painful stimulus, will predict the intensity of the consecutive
      painful stimulus (low vs. high) with a probability of 75%. After each painful stimulus,
      participants will be asked to rate the perceived pain intensity. Electroencephalography (EEG)
      and skin conductance will be recorded continuously during anticipation and stimulation
      intervals. This paradigm enables us to compare pain-associated brain responses of validly and
      invalidly cued trials, i.e. the representation of the prediction error, on the one hand. On
      the other hand, brain activity related to predictions can be investigated in the anticipation
      interval preceding to the painful stimulus by comparing trials with low and high intensity
      cues. Further, we will compare models including predictions, prediction error and sensory
      evidence to ascertain the involvement of each brain response in processing sensory
      information and expectation. Results of the study promise to elucidate the interplay of
      predictions, predictions errors and sensory evidence in pain processing and how they
      differentially relate to neural oscillations at different frequency bands and pain-evoked
      responses.
    

Detailed description: 
      Not needed
    

Intervention name(s): Painful stimulation using a laser device (DEKA Stimul 1340, Calenzano, Italy); Visual cueing
Intervention type(s): Device; Device
Intervention description(s): In the experimental paradigm, 160 painful stimuli of two intensities (3 J, 3.5 J) will be applied to the dorsum of the left hand using the laser device listed above.; Preceding to each painful stimulus, visual cues (e.g., blue dot and yellow square) will be presented on a screen indicating the intensity of the subsequent stimulus (low and high intensity) with an accuracy of 75%. The contingencies of the visual cues will be explicitly stated to the participants.
Intervention model: Single Group Assignment
Intervention model description: Each participant will participate in one experimental session with a duration of 40 minutes. The experimental paradigm consists of 160 painful stimuli of two intensities (low and high), which will be applied using a laser stimulation device (DEKA Stimul 1340, Calenzano, Italy). Preceding to each painful stimulus, visual cues will be presented indicating the intensity of the subsequent stimulus with an accuracy of 75%. After each painful stimulus, participants will be prompted to verbally rate the pain intensity on a scale ranging from 0 ('no pain') to 100 ('maximum tolerable pain'). Brain activity and autonomic activity will be recorded simultaneously using EEG and skin conductance responses (SCRs), respectively.
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: pain; electroencephalography; laser-evoked potentials; neural oscillations; brain; predictive coding