August 2023
Volume 23, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2023
The visual representation of pain facial expressions: a high-definition transcranial direct current stimulation study
Author Affiliations & Notes
  • Marie-Claude Desjardins
    University of Québec in Outaouais
  • Daphnée Sénécal
    University of Québec in Outaouais
  • Sara Tremblay
    University of Québec in Outaouais
    Neuromodulation Research Clinic, Royal's Institute of Mental Health Research
    Department of Cellular and Molecular Medicine, University of Ottawa
  • Daniel Fiset
    University of Québec in Outaouais
  • Francis Gingras
    University of Québec in Outaouais
  • Caroline Blais
    University of Québec in Outaouais
  • Footnotes
    Acknowledgements  This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada (RGPIN-2019-06201) and the Canadian Research Chair in cognitive and social vision (# 950-232282).
Journal of Vision August 2023, Vol.23, 5324. doi:
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      Marie-Claude Desjardins, Daphnée Sénécal, Sara Tremblay, Daniel Fiset, Francis Gingras, Caroline Blais; The visual representation of pain facial expressions: a high-definition transcranial direct current stimulation study. Journal of Vision 2023;23(9):5324.

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      © ARVO (1962-2015); The Authors (2016-present)

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As pain and empathy neural signatures share a great deal of resemblance, this social competence has often been linked to the adequacy of pain estimation, a highly adaptive yet frequently inaccurate perceptual skill. It was recently suggested that the neurostimulation of the right inferior frontal gyrus (rIFG), a key region of this network, could temporarily alter empathic abilities. Nonetheless, the impact of these neural processes on pain perception in faces, namely the estimation bias and the ability to detect the expression’s fine variations (called sensitivity) remains unclear. We applied high-definition transcranial direct current stimulation over the rIFG of 22 participants but previous results of empathy diminution, as measured by the Multifaceted Empathy Test, were not replicated in the present study [𝘍(2, 42)=.57, 𝘱=.57]. Visual representations (VRs) of pain facial expressions were extracted using the data-driven method Reverse correlation. Pixel-by-pixel analyses were conducted: a repeated measure ANOVA showed no effect of stimulation conditions [𝘱’s≥.24] but a one-sample t-test confirmed the presence of facial features typically associated with pain percept in our participants’ VR [𝘛𝘤𝘳𝘪𝘵=2.3, 𝘬=461, 𝘱<.05]. These classification images were then submitted to the OpenFace algorithm which revealed classical pain signals were almost systematically activated (AU4, AU7, AU9 & AU10). Noticeably, these VRs were still rated as primarily expressing disgust, sadness, and anger by an independent group (𝘕=30). Additionally, our sample exhibited a clear underestimation tendency [𝜇=-1.54], a suboptimal sensitivity level [𝜇=-.40], and these two parameters were not correlated [𝘳=-.26, 𝘱=.24], thus replicating previous work. The degree of variability revealed in the visual representations, as well as the ambiguity they seem to generate, may reflect some overlap in emotional representations. It would be interesting to explore the variability in those overlaps and assess how it may influence individuals’ ability to estimate pain.


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