Abstract
The thermal grill illusion (TGI) is a paradoxical perception of burning heat and pain resulting from the simultaneous application of interlaced warm and cold stimuli to the skin. The TGI is considered a type of chronic centralized pain and has been used to apply nociceptive stimuli without inflicting harm to human participants in the study of pain mechanisms. In addition, the TGI is an interesting phenomenon for researchers, and various topics related to the TGI have been investigated in several studies, which we will review here. According to previous studies, the TGI is generated by supraspinal interactions. To evoke the TGI, cold and warm cutaneous stimuli should be applied within the same dermatome or across dermatomes corresponding to adjacent spinal segments, and a significant difference between cold and warm temperatures is necessary. In addition, due the presence of chronic pain, genetic factors, and sexual differences, the intensity of the TGI can differ. In addition, cold noxious stimulation, topical capsaicin, analgesics, self-touch, and the presence of psychological diseases can decrease the intensity of the TGI. Because the TGI corresponds to chronic centralized pain, we believe that the findings of previous studies can be applied to future studies to identify chronic pain mechanisms and clinical practice for pain management.
Highlights
The thermal grill illusion (TGI) is a paradoxical perception of burning heat and pain resulting from the simultaneous application of interlaced warm and cold stimuli to the skin
The TGI is considered a type of chronic centralized pain
We reviewed mechanisms and phenomena related to the TGI
Summary
The thermal grill illusion (TGI), first introduced in 1896, is the perception of burning heat and pain that arises from the simultaneous cutaneous application of a grill with interlaced warm (38–42 ◦ C) and cool (18–22 ◦ C) bars [1,2,3]. The TGI has been used to apply nociceptive stimuli without inflicting harm to human participants in studies investigating pain mechanisms [5,6]. A review of these previous studies would be meaningful because the findings of previous studies could be used to investigate the characteristics or mechanisms of chronic pain in future studies and applied to real clinical practice for managing chronic pain.
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