Figure 1.

(a) Burn intensity ratings: average perceived intensity of burning sensation (y axis) after delivery of capsaicin and tasteless rinses (x axis) in subjects included in fMRI analysis (n = 16). Burning sensation returns to zero by the fifth rinse for all subjects. Error bars represent 1 standard deviation. (b) Depiction of taste events: Cue = subject hears cue that liquid will be delivered. T = delivery of one of the 3 tastes over 3 s. Taste event = 18-s event of interest. Swal = time during which the tone plays signaling subject to swallow; R = delivery of the tasteless solution over 3 s. Rinse event = 18-s event modeled as tasteless baseline for fMRI analysis. (c) Signal change in response to capsaicin stimulation: Pilot data showing raw evoked response in percent signal change to a capsaicin event in the postcentral gyrus (y axis) in one subject plotted as a function of time (x axis, in seconds). Maximal hemodynamic response to capsaicin occurs 4 s after the swallow and resolves 13 s later. (d) Capsaicin event: Cap = capsaicin delivery over 3 s; For fMRI analysis, the capsaicin event is modeled as the event of interest, the tasteless5 as the baseline and the cue, swallow, and tasteless1–4 as events of no interest.