Brain Activation Associated With Changes in Heart Rate, Heart Rate Variability, and Plasma Catecholamines During Rectal Distention

intermittently inflated with 0, 20, or 40 mm Hg at random for 80 seconds. H2 15 O positron emission tomography (PET) of the brain, electrocardiography, and blood sampling for catecholamines were performed. Changes in regional cerebral blood flow were interpreted using statistical parametric mapping. Results: Rectal distention with 40 mm Hg induced a significant increase in heart rate, low frequency (LF)/high frequency (HF) ratio of heart rate variability, and plasma adrenaline. Activated brain areas that were associated with increased heart rate during rectal distention were the right insula, right operculum, right dorsolateral prefrontal cortex, putamen, thalamus, periaqueductal gray, and cerebellum (p .001, uncorrected), whereas those that were associated with an increased LF/HF ratio were the bilateral insula, putamen, thalamus, midbrain, pons, and cerebellum (p .001, uncorrected). Activated brain areas that were associated with increased plasma adrenaline were the right insula, right orbitofrontal cortex, right parahippocampal gyrus, putamen, thalamus, periaqueductal gray, pons, and cerebellum (p .001, uncorrected). Conclusion: Our results suggest that the right insula and the related body mapping regions may form the functional module of sympathetic arousal in response to gut stimulation. Key words: positron emission tomography, heart rate, heart rate variability, catecholamine, visceral perception, rectal distention. PET positron emission tomography; rCBF regional cerebral blood flow; SPM statistical parametric mapping; BA Brodmann’s area; ECG electrocardiogram; HRV heart rate variability; HF high frequency component of HRV; LF low frequency component of HRV; LF/HF ratio of LF to HF; ANOVA analysis of variance; MRI magnetic resonance imaging.