Figure 1.

Activations and deactivations for the CO₂ FM scans compared with the O₂ FM scans displayed on the average MR brain image of the nine subjects. (a) Extensive midbrain and brainstem activations (arrowed) (x = 0; z = −8), medial frontal and large posterior cingulate deactivations (x = 0), and bilateral middle frontal gyri deactivations (z = −8). (b) Hypothalamus (arrowed), brainstem, and cerebellum activations (x = 8), and highly significant bilateral amygdala activations (arrowed) (y = −12). The positive and negative Z-score color coding is shown.