Figure 2.

(a) Differential map (PAIN–REST) for the HF-HRV/fMRI analysis of the entire (6 min) runs. Group maps are compared with graphical representations of brainstem nuclei as in the Duvernoy atlas [31] (white squares indicate the correspondence on the functional maps). A significant difference between REST and PAIN conditions was found in the pontine nuclei (Pn), the rostral ventromedial medulla (RVM) and the nucleus reticularis medullae oblongatae centralis, including the nucleus ambiguus (Rt/NAmb). (b) Normalized values of HF-HRV power (black line) and BOLD signal from Rt/NAmb (grey line) from a representative subject during a REST and a PAIN run. (c) Per cent signal change from the significant clusters showing a reduction in the negative correlation (Gi/RVM cluster) or a shift to positive correlation (Pn and Rt/NAmb clusters) during PAIN. Bar plot error bars represent s.e.m.