Frequency-Tagging Captures Distinct Neural Responses Elicited by Bilateral Periodic Thermonociceptive Stimulation

Sustained periodic stimuli are known to elicit a periodic neural response (i.e., steady-state evoked potential) in the EEG frequency spectrum. These responses can easily be traced at their frequency of stimulation and corresponding harmonics using a frequency-tagging approach. To date, sustained periodic thermonociceptive stimuli have only been used on one extremity (e.g., right volar forearm) at a time. Extending this procedure to sustained stimulation applied concomitantly to distinct limbs would allow us to study the mechanisms of integration or competition between sensory signals from these different body locations. This study demonstrates that slow, sustained, sinusoidal thermonociceptive stimuli, bilaterally applied using two different stimulation frequencies (i.e., f₁, f₂, one on each forearm), elicit two distinct neural periodic responses at the respective frequency of stimulation and their harmonics. Additionally, we showed preliminary evidence for an interaction between the neural populations involved in the response to these stimuli, marked by neural activity at intermodulation frequencies (n* f₁ ± m* f₂). While encouraging, further studies designed specifically to tease out these intermodulation responses are needed to corroborate our findings.