University of Twente Student Theses


The Role of the Nociceptive Detection Criterion and Conscious Perception of Nociceptive Stimuli Evaluated During Psychophysical Tasks

Vanwinsen, Leen (2021) The Role of the Nociceptive Detection Criterion and Conscious Perception of Nociceptive Stimuli Evaluated During Psychophysical Tasks.

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Abstract:About 20% of European citizens suffers from chronic pain, making it a big burden to society and individuals. For the majority of them, no sufficient diagnostic and treatment tools are available, mainly because there is a lack of knowledge in the mechanisms underlying chronic pain. The nociceptive system is the sensory system that is responsible for pain. To obtain more understanding on nociceptive processing, the BSS group of the University of Twente has developed the ND-TEP method. This psychophysical method is able to simultaneously track the nociceptive detection probability and evoked potentials (EPs) following nociceptive stimuli. From the nociceptive detection probability, characteristics of the nociceptive system can be obtained, like the nociceptive detection threshold (NDT), slope and NDT drift. The EPs following nociceptive stimuli carry valuable information about nociceptive processing in the cortex. Characteristic for nociceptive stimuli are an N1 reflecting early sensory processing and the N2-P2 wave reflecting the perception of the stimulus. The NDT-EP method uses a Go/No-Go (GNG) procedure where a subject indicates the conscious perception of the stimuli with a button. Whether the sensory evidence of a stimulus is converted into a conscious perception depends on the detection criterion. This is not a fixed criterion, and it can change due to several factors, e.g. attention. The detection criterion can possibly cause a bias in the measurements of the NDT-EP method. This bias could be enabled by the GNG procedure. In this thesis, conscious perception of nociceptive stimuli was investigated, and the nature and influence of the detection criterion on conscious perception was explored. Also, a method to completely circumvent a possible subjective detection criterion bias was investigated. In an experiment on fifteen healthy subjects, the bias free 2-IFC procedure and the GNG procedure were performed. Inspecting the detection probability, and the EPs for both procedures, a bias was detected in the measurements of the GNG procedure. This bias was visible for single pulse stimuli in the NDT, slope and NDT drift. In the EP, a significant P2 arose for not detected stimuli of the GNG procedure, indicating the perception of the stimulus without a button release, and therefore a bias. In a proof-of-principle experiment on eight healthy subjects, using an automatic and real-time tracking algorithm to obtain the nociceptive detection probability based on brain activity was explored. This algorithm is able to classify epochs of EEG data as being poststimulus or not. It therefore replaces the response of the subject during the NDT-EP method, and bases its response solely on physiological signals, preventing the subjective bias caused by the detection criterion. Very promising results were obtained, and the NDT-EP method with the algorithm gave similar results as the GNG procedure. In conclusion, the detection criterion transferring sensory evidence of a nociceptive stimuli into the conscious perception of the stimuli, can cause a bias. This bias is enabled by the experimental procedure, which should be taken into account when performing NDT-EP experiments. The subjective component of the bias can be prevented by using an automatic tracking algorithm.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:42 biology
Programme:Biomedical Engineering MSc (66226)
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