Background & Aims

The population coding account of pain proposes that a distributed network of neural activity across both nociceptive and non-nociceptive domains drives our experience of thermosensation and pain1,2. Recent pioneering work in mice shows that distinct neuronal population codes for cold and warm thermal perception exist in the posterior insula cortex3 (pIC). In this study we used functional magnetic resonance imaging (fMRI) to model the pattern of response associated with innocuous and noxious thermal stimuli, to determine whether similar population receptive fields (PRFs) for temperature and pain exist in the human brain.

Methods

Individual detection and pain thresholds for each participant (N = 38) were used to generate two temperature continua (warm and cold) which each consisted of seven perceptually distinct temperatures of increasing thermal intensity. At least two temperatures on each continuum were above the individual’s pain thresholds. In the MRI scanner, temperatures were presented on the right volar forearm of each participant, with a ramp rate of 40º/sec and a peak stimulus duration of 2.5 secs. After stimulation, participants were required to indicate whether the stimulus caused burning (yes or no), was warm or cold and to rate the overall intensity of the stimulus on a VAS from 0 – 100.

Results

Group-level analyses reveal clusters of activity within the left somatosensory cortex, insula and thalamus in response to both innocuous and noxious stimuli. Next, we will extract thermosensory neuronal pRFs by modelling the shape of the BOLD response along each temperature continuum in each participant4. This allows us to determine how the pattern of response in brain regions such as the pIC or thalamus changes with stimulus intensity, temperature, nociception or pain.

Conclusions

This study is poised to offer novel insights into the neural coding of temperature, nociception and pain, potentially reshaping our understanding of thermosensation in humans. The use of pRF mapping allows for individual characterisation of stimulus response, providing a deeper understanding of the subjective experiences of temperature and pain.

References

1.Coghill, R. C. The Distributed Nociceptive System: A Framework for Understanding Pain. Trends Neurosci. 43, 780–794 (2020).
2.Fardo, F., Beck, B., Allen, M. & Finnerup, N. B. Beyond labeled lines: A population coding account of the thermal grill illusion. Neurosci. Biobehav. Rev. 108, 472–479 (2020).
3.Vestergaard, M., Carta, M., Güney, G. & Poulet, J. F. A. The cellular coding of temperature in the mammalian cortex. Nature 614, 725–731 (2023).
4.de Haas, B. et al. Perception and Processing of Faces in the Human Brain Is Tuned to Typical Feature Locations. J. Neurosci. 36, 9289–9302 (2016).

Presenting Author

Alexandra G. Mitchell

Poster Authors

Alexandra Mitchell

PhD

Aarhus University

Lead Author

E-mail

Benjamin De Haas

PhD

Justus Liebig University Giessen

Lead Author

E-mail

Camila Sardeto Deolindo

PhD

Aarhus University

Lead Author

E-mail

Arthur Courtin

Aarhus University

Lead Author

E-mail

Camilla Eva Krænge

MSc

Aarhus University

Lead Author

E-mail

Maëlle Debock

MSc

University of Montpellier

Lead Author

E-mail

Micah G. Allen

Ph.d.

Center of Functionally Integrative Neuroscience, Department of Clinical Medicine, Aarhus University

Lead Author

E-mail

Francesca Fardo

Aarhus University

Lead Author

E-mail

Topics

  • Pain Imaging