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 paradigm to a bilateral application would enable its use to study the sensory integration of concomitant nociceptive stimuli and cognitive modulations during e.g. spatial attention tasks. This study demonstrates that slow sustained sinusoidal thermonociceptive stimuli, bilaterally applied using two different frequencies (i.e. f ₁ , f ₂ , 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* f ₁ ± m* f ₂ ). So far, this non-linear integration of sensory information has already been observed following visual and auditory stimuli, but not yet following thermonociceptive stimuli.