P3-specific amplitude reductions to respiratory and auditory stimuli in subjects with asthma.

The respiratory-related evoked potential (RREP) is the electroencephalographic response to brief inspiratory occlusion. The P3 component of the response reflects the active cognitive processing of stimulus information. This study investigated the RREP in 16 subjects with asthma and 16 control subjects. In addition, auditory-evoked potentials were recorded using an oddball paradigm in both groups and were compared with the RREP results. Perceptual sensitivity was assessed using a load magnitude estimation task, whereby subjects estimated the magnitude of four added resistive loads using a modified Borg scale. For RREP assessment, inspiratory occlusions were presented for 200 milliseconds. For auditory-evoked potential assessment, 1,000- and 2,000-Hz pure tones were presented at 60 dB for 100 milliseconds, with the 2,000-Hz tone presented with 20% probability and identified as a target stimulus. Scalp electroencephalographic activity was measured from 29 channels. Resistive load intensity was linearly related to magnitude estimation in both subjects with asthma (r2 = 0.96) and control (r2 = 0.99) subjects. Results showed that both the respiratory and auditory P3 components were markedly reduced in the group with asthma compared with the control group. Other components were similar between the groups. These results suggest an intrinsic reduction in P3 amplitude for patients with asthma, which may relate to differences in processing perceptual information.