Figure 1.

Experimental protocol for fMRI studies. Top schematic, An example of the four functional runs that were performed for each subject, consisting of three presentations of each condition. A classic 2 × 2 factorial design (no cough/cough and no capsaicin/capsaicin) was used to assess brain BOLD responses for saline challenge, voluntary cough, capsaicin-evoked cough, suppression of evoked cough, and the interaction between capsaicin challenge and coughing. Bottom schematic, An expanded view of one challenge. A brief visual cue was used to prepare (P) for challenge and to instruct subjects how to respond (i.e., “cough” or “don't cough”), followed by a “Go Cue” during which capsaicin or saline was blindly presented. Challenges were timed so that the nebulized gas reached the subject precisely at the onset of a single maximal inspiratory effort and was then replaced by medical air immediately at the peak of inspiration. Subjects performed the required task and then breathed normally (Rest) until the next preparatory cue. Rest periods were variable in duration between 18 and 36 s.