Background & Aims
Intracerebral electroencephalography recordings from the posterior insula have shown that ongoing neural oscillations in the theta and alpha frequency bands are selectively modulated by sustained periodic nociceptive stimuli (Liberati et al. 2019). These findings suggest a relationship between nociception and ongoing oscillations in the posterior insula, but it remains unclear whether these modulations play a significant role in the perception of pain. If this is the case, cognitive processes known to affect pain perception (such as attention (Torta et al. 2017)) should also affect these ongoing oscillations. To investigate this link, we assessed the effect of an arithmetic distraction task on both perceived pain intensity and the modulation of ongoing oscillations in the insula measured using iEEG.
Methods
7 patients (34 ± 8 years old, 2 female) who had depth electrodes implanted in the anterior (n=28) or posterior (n=16) insula as part of their pre-surgical evaluation for refractory epilepsy were recruited. Slow periodic sustained thermonociceptive and non-nociceptive vibrotactile stimuli were applied in separate trials at a frequency of 0.2 Hz, allowing us to “frequency-tag” the neural responses related to the stimuli (Leu et al., 2023 ; Liberati et al., 2019). The arithmetic task consisted of continuously subtracting 7 from a 3-digit starting number throughout the stimulation. After each stimulus, the patients provided a rating of perceived stimulus intensity on a numerical rating scale. The modulation of ongoing oscillations was assessed in the theta (4-8 Hz) and alpha (8-12 Hz) frequency bands. Linear mixed models assessed the impact of condition, modality, and electrode location on perceived stimulus intensity and modulation of ongoing oscillations for each frequency band.
Results
During the arithmetic task, perceived stimulation intensity was significantly decreased in both modalities (thermonociceptive: p=0.013, vibrotactile: p=0.00 02). Following thermonociceptive stimuli, the modulation of ongoing oscillations was significantly larger in the posterior than in the anterior insula during baseline condition in the theta (p<0.0001) and alpha (p<0.0001) frequency band. This difference was not present during the distraction task. Following vibrotactile stimuli, the posterior insula always exhibited a larger modulation than the anterior insula (theta: p=0.001, alpha: p=0.007). Additionally, the arithmetic task led to a significant reduction in the modulation at the frequency of stimulation for thermonociceptive stimuli in the theta (p=0.004) and alpha (p=0.008) frequency band. No differences between the conditions were found in the vibrotactile modality.
Conclusions
The concomitant decrease in amplitude and intensity perception during thermonociceptive stimulation and the lack of such a relationship during vibrotactile stimulation might reflect the preferential modulation of thermonociceptive stimuli within the posterior insula and illustrates its potential functional relationship with pain perception.
References
Leu, C., Courtin, A., Cussac, C., & Liberati, G. (2023). The role of ongoing oscillation in pain perception: Absence of modulation by a concomitant arithmetic task. Cortex, 168, 114-129. https://doi.org/https://doi.org/10.1016/j.cortex.2023.08.005
Liberati, G., Algoet, M., Santos, S. F., Ribeiro-Vaz, J. G., Raftopoulos, C., & Mouraux, A. (2019). Tonic thermonociceptive stimulation selectively modulates ongoing neural oscillations in the human posterior insula: Evidence from intracerebral EEG. NeuroImage, 188, 70-83. https://doi.org/https://doi.org/10.1016/j.neuroimage.2018.11.059
Torta, D. M., Legrain, V., Mouraux, A., & Valentini, E. (2017). Attention to pain! A neurocognitive perspective on attentional modulation of pain in neuroimaging studies. Cortex, 89, 120-134. https://doi.org/https://doi.org/10.1016/j.cortex.2017.01.010
Presenting Author
Chiara Leu
Poster Authors
Topics
- Assessment and Diagnosis