Figure 2.

Group averaged responses during Valsalva and breath hold challenges. (A–G) Responses when the breath hold duration is always 20 seconds, but intrathoracic pressure is changing. The vertical dashed lines show the onset and offset of the hold, and the inset shows the signals after the breath hold after the exhalation response is subtracted from the other responses. The inset boxes are proportionally scaled from the larger figures. (H–N) Responses when intrathoracic pressure is always 30 mm Hg, but the breath hold duration is changing. The black dashed line is the onset of the breath hold, and the colored dashed lines mark the end of each breath hold duration. In all regions of interest, the magnetic resonance imaging (MRI) responses decreased below baseline (the valley) during the hold, and increased to a peak after the end of the hold. The magnitude of the responses scaled with thoracic pressure. CSF, cerebrospinal fluid.