Neural oscillatory markers of respiratory sensory gating in human cortices.

Background: Human respiratory sensory gating is a neural process associated with inhibiting the cortical processing of repetitive respiratory mechanical stimuli. While this gating is typically examined in the time domain, the neural oscillatory dynamics, which could offer supplementary insights into respiratory sensory gating, remain unknown. The purpose of the present study was to investigate central neural gating of respiratory sensation using both time- and frequency-domain analyses.

Methods: A total of 37 healthy adults participated in this study. Two transient inspiratory occlusions were presented within one inspiration, while responses in the electroencephalogram (EEG) were recorded. N1 amplitudes and oscillatory activities to the first stimulus (S1) and the second stimulus (S2) were measured. The perceived level of breathlessness and level of unpleasantness elicited by the occlusions were measured after the experiment.

Results: As expected, the N1 peak amplitude to the S1 was significantly larger than to the S2. The averaged respiratory sensory gating S2/S1 ratio for the N1 peak amplitude was 0.71. For both the evoked- and induced-oscillations, time-frequency analysis showed higher theta activations in response to S1 relative to S2. A positive correlation was observed between the perceived unpleasantness and induced theta power.

Conclusions: Our results suggest that theta oscillations, evoked as well as induced, reflect the "gating" of respiratory sensation. Theta oscillation, particularly theta-induced power, may be indicative of the emotional processing of respiratory mechanosensation. The findings of this study serve as a foundation for future investigations into the underlying mechanisms of respiratory sensory gating, particularly in patient populations.