The present study investigated the effect of target stimulus probability on the P3 component of the respiratory-related evoked potential (RREP). A single respiratory stimulus paradigm was employed where normal breaths served as standard stimuli and occluded breaths presented at various probability levels served as target stimuli. EEG was recorded from 29 channels in young adults in two conditions. In Condition 1, occlusions were presented at target probabilities of 0.5, 0.33, 0.25, 0.2, 0.1, and 0.05, that is, every 2nd, 3rd, 4th, 5th, 10th, and 20th breath. Order of target probability presentation varied randomly. Condition 2 used the same target probabilities, but held breathing rate constant by using a paced respiration task. Results indicated that P3 amplitude was significantly affected by stimulus probability, such that the component showed an inverse relationship with probability. This effect was similar between conditions. However, P3 amplitude reduced and latency increased when the secondary task of paced respiration was introduced. These data suggest that models developed to describe the effect of stimulus probability on the amplitude of visual and auditory P3 components are applicable to the respiratory somatosensory modality.

The present study assessed the effects of occlusion duration and attention on components of the respiratory-related evoked potential (RREP). Twenty-nine channel evoked potential recordings were obtained from 12 young adults exposed to a pseudorandom sequence of 100-, 200-, 400-, and 800-ms inspiratory occlusions, under attend and ignore conditions. Results demonstrated that the duration of an inspiratory occlusion does not affect RREP components systematically, highlighting the importance of the onset of the occlusion in producing the cortical responses. Attention resulted in augmentation of the N1, P2, and P3 components but did not affect the early latency Nf and P1 components. P1, N1, and P3 occurred with shorter latencies in the attend condition. One subject with poor duration estimation ability displayed substantially delayed P3 latency. This result highlights the relationship between P3 and perception of respiratory somatosensory information.