Experimental Pain in Healthy Human Participants
Conditions
Keywords
pain, electroencephalography, laser-evoked potentials, neural oscillations, brain, predictive coding
Brief 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
Interventions
DEVICEPainful stimulation using a laser device (DEKA Stimul 1340, Calenzano, Italy)
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.
DEVICEVisual cueing
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.
Sponsors
German Research Foundation
Technical University of Munich
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Masking description
Participants will not be informed about the objective intensities of the painful stimuli as being binary.
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.
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
Yes
Inclusion criteria
* Age 18-65 years * Right-handedness * Written informed consent
Exclusion criteria
* Pregnancy * Neurological or psychiatric diseases (e.g. epilepsy, stroke, depression, anxiety disorders) * Severe general illnesses (e.g. tumors, diabetes) * Skin diseases (e.g. dermatitis, psoriasis or eczema) * Current or recurrent pain * Regular intake of medication * Surgical procedures involving the head or spinal cord * Metal (except titanium) or electronic implants * Side-effects following previous thermal stimulation
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Verbal pain rating (NRS; 0: 'no pain' to 100: 'maximum tolerable pain') | During 40 minutes of the experimental paradigm | 160 painful stimuli will be applied to the participants' left hand. Participants will be asked to verbally rate the perceived pain intensity of each stimulus on a numerical rating scale (see above). |
| Oscillatory and evoked brain responses pre- and post-stimulus | During 40 minutes of the experimental paradigm | EEG including 64 channels will be recorded. In offline analyses, power of oscillatory brain activity will be quantified in the alpha (8-13 Hz), beta (14-30 Hz) and gamma (60-100 Hz) frequency bands. In addition, laser-evoked potentials (LEPs) will be quantified with regard to amplitudes and latencies. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| SCRs (µS) | During 40 minutes of the experimental paradigm | SCRs will be recorded using two electrodes attached to the index and middle finger of the left hand. |
Countries
Germany
Outcome results
None listed