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.