Predictive Timing in Pain

2524 

Abstract Submission 

Andreas Strube¹, Christian Büchel²

¹University Medical Center Hamburg-Eppendorf, Hamburg, Hamburg, ²University Medical Center Hamburg Eppendorf, Hamburg, Hamburg

Andreas Strube  
University Medical Center Hamburg-Eppendorf
Hamburg, Hamburg

Christian Büchel  
University Medical Center Hamburg Eppendorf
Hamburg, Hamburg

A key factor in the expectation of events is when an event will occur (e.g. Arnal & Giraud, 2012). This seems to be particularly the case with aversive factors that we want to avoid for our own protection. In an EEG study (N =35), we applied experimental phasic painful heat stimuli and non-painful cold stimuli and announced in advance for each stimulus whether the next stimulus would be applied immediately, early or late. In some cases, this cue was not reliable. This allows us to make statements about two important fields of research: First, can we find a signature in brain activity for predictive timing, i.e., temporal expectations and expectation errors? Second, does this allow us to draw conclusions about the role of expectations in the so-called dread effect - which shows that people choose to experience painful stimuli sooner rather than later (e.g. Story et al., 2013).

In this study, participants were confronted with painful heat stimuli and non-painful cold stimuli (4s stimulation / for heat stimuli: 46.5°C / for cold stimuli: 20.5°C). Before each stimulus, a cue announced whether the next stimulus would be applied immediately (0s), early (2s) or late (4s). These cues were not always reliable: In 50% of the cases, the cue correctly predicted the temporal contingency. In 25% of the cases, the temporal contingency was not correct. In the remaining 25% of cases, a catch trial was performed instead of the presentation of a stimulus. Participants had to rate the intensity of the stimulus after each stimulus. In addition, during the catch trials, participants had to report which cue they had just seen.

An analysis of the intensity ratings showed that late expectations - regardless of the true temporal contingency of the stimuli - led to a significant increase in pain ratings. In contrast, the latency of the pain stimulus had no influence on pain ratings. A time-frequency analysis of the EEG data revealed that pain timing during pain application is encoded in a cluster in the theta band (4-8Hz) and in a cluster in the alpha-to-beta band (8-30Hz) - the greater the latency, the stronger the desynchronization in both clusters. Immediately after the cue, the timing expectation is represented in the alpha-to-beta band (8-30Hz). Expectation errors were encoded in a synchronization of theta (4-8Hz) and gamma band (>30Hz) activity.

In this study, we were able to show that late expectations regarding the latency of a pain stimulus are already sufficient to increase the intensity of the pain stimulus. This is in contradiction to ideas that the latency to the stimulus leads to an increase in the pain stimulus. Furthermore, in this study we were able to show that predictive timing components were represented in the EEG and that typical pain signals are modulated by them.

EEG ²

Perception: Pain and Visceral ¹

Perception: Tactile/Somatosensory

Electroencephaolography (EEG)

Pain

Somatosensory