Increased activity of the temporal insula in subjects with bradycardia

Though it has been postulated that cortical brain regions participate in th e regulation of heart rate, their involvement is poorly understood. Using P ET and [18] FDG (to measure regional brain glucose metabolism, which serves as an index of brain function) we compared the regional brain metabolic ac tivity between healthy subjects with bradycardia (<60 beats per minute) wit h those with normal heart rates in the 75-100 beats per minute range. Stati stical Parametric Mapping (SPM) analyses revealed significant differences b etween the groups predominantly localized to the temporal insula, This find ing was corroborated by a separate analysis that measured the metabolic act ivity for each subject in preselected regions located in the temporal insul a. Subjects with bradycardia had significantly higher metabolic activity in the right (p < 0.0001) and in the left temporal insula (p < 0.015) than th ose with normal heart rates. Moreover, resting heart rates were negatively correlated with metabolism in the right (r = -0.77, p < 0.0001) and in the left temporal insula (r = -0,44, p < 0,05). These results corroborate the i mportance of the temporal insula in the regulation of resting heart rate in humans. The temporal insula is interconnected with limbic brain region and autonomic centers and suggests that this may be a mechanism by which emoti onal responses regulate heart rate. (C) 2000 Elsevier Science Inc. All righ ts reserved.