Fig. 3.

Signal analysis in the brainstem.A, Activation map in the brainstem. Shown is the activation map within the brainstem after the 46°C stimulus. The area indicated in red (2) is the activated zone, and the panels above (1), below (3), and opposite (4) the area activated (2) are also shown.B, Signal validation. The gray region in all the time course graphs indicates the 46°C stimulus duration. The panels show time courses of signal change within a three-voxel region, which matches the thermal stimulus temporally. The time courses for activity within brainstem regions of equal volume superior (1), inferior (2), and contralateral (3) to the activated zone (4) are shown. Percent signal change is shown in arbitrary units (a.u.). C, Fourier analysis. Shown is Fourier analysis for the thermal signal itself (TSA; top panel) and for the adjacent and contralateral signal changes shown in A for brainstem sites 1–4. The Fourier analyses indicate that other frequency changes are present, which may be respiratory or cardiac. Note, however, that contributions to the signal are present but not significant in the voxels above and below the activation.