Background & Aims

Habituation and sensitization to pain are response decrements or increments, respectively, resulting from repeated painful stimulation [1]. These effects have been shown using self-report rating scales, EEG and fMRI [2]. So far, research using pain ratings and skin conductance responses in this field have mostly emphasized group effects, without acknowledging individual differences. In addition, the reliability of these individual patterns over several sessions is unclear. Individual variability is important to be able to further investigate the potential of habituation measures as a treatment target for chronic pain [3]. In this context, test re-test reliability of these paradigms using repeated painful stimulation is crucial. Together, we aim to investigate individual differences in habituation and sensitization to pain measured with the use of pain intensity ratings and skin conductance responses and their test re-test reliability over two sessions.

Methods

Healthy participants (n=54) received painful stimulation during two sessions, separated by four weeks. In each session, they received three runs of 25 painful electrical stimuli on the left middle finger. After each stimulus, participants rated their pain on a numeric rating scale. Skin conductance was acquired at the palm of their hands. Electrical stimuli had a duration of 10 ms and were individually calibrated to 50% above participants’ reported pain threshold. The 75 stimuli were all of the same intensity with an interstimulus interval of 18-24s. For skin conductance data, peak amplitudes were extracted using Ledalab [4]. Data was analyzed in R. Individual linear regression models were fitted to the behavioral pain ratings and skin conductance amplitudes (within and across runs) to define habituation (slope < 0), no change (slope not significantly different from 0) and sensitization (slope > 0). Test re-test reliability was calculated using the intra-class coefficient (ICC).

Results

Participants showed large individual differences in pain ratings across stimulation runs for
both sessions, reflecting either habituation, no change or sensitization. Test re-test reliability was poor for across-run (0.31) and moderate for within-run habituation and sensitization (0.51). Correlations between individual ratings across sessions were highest for sensitizers. Skin conductance responses habituated across runs for all participants but not between sessions. Individual peak amplitudes showed poor reliability across sessions. Non-response trials significantly increased within a session. Overall, pain ratings and skin conductance amplitudes showed a moderate correlation (r = 0.27).

Conclusions

This study demonstrated that repeated painful stimulation resulted in different subgroups of participants showing habituation, no change or sensitization for pain intensity ratings. Skin conductance responses habituated for all participants within a session and were moderately correlated to pain ratings. These measures therefore likely reflect different aspects of habituation and sensitization processes. Test re-test reliability was poor to moderate for pain ratings and poor for skin conductance responses. Interestingly, participants that sensitized showed more stable patterns across time, which could potentially indicate a maladaptive process. Follow-up research will explore interventions aimed at these patterns.

References

1. Rankin, C. H., Abrams, T., Barry, R. J., Bhatnagar, S., Clayton, D. F., Colombo, J., … & Thompson, R. F. (2009). Habituation revisited: an updated and revised description of the behavioral characteristics of habituation. Neurobiology of learning and memory, 92(2), 135-138.

2. van der Miesen, M. M., Joosten, E. A., Kaas, A. L., Linden, D. E., Peters, J. C., & Vossen, C. J. (2023). Habituation to pain: self-report, electroencephalography, and functional magnetic resonance imaging in healthy individuals. A scoping review and future recommendations. Pain, 10-1097.

3. van der Miesen, M. M., Vossen, C. J., & Joosten, E. A. (2023). Habituation to Pain in Patients with Chronic Pain: Clinical Implications and Future Directions. Journal of Clinical Medicine, 12(13), 4305.

4. Benedek, M., & Kaernbach, C. (2010). A continuous measure of phasic electrodermal activity. Journal of neuroscience methods, 190(1), 80-91.

Presenting Author

Maite van der Miesen

Poster Authors

Maite van der Miesen

MSc

Maastricht University

Lead Author

David Linden

Lead Author

Carine Vossen

Lead Author

Judith Eck

Lead Author

Bert Joosten

Lead Author

Judith Peters

Lead Author

Topics

  • Assessment and Diagnosis