BRADYCARDIA AND TACHYCARDIA FOLLOWING ELECTRICAL STIMULATION OF THE AMYGDALOID REGION IN MONKEY

Abstract

Electrical stimulation in the amygdaloid region of chronically prepared squirrel monkeys may result in either bradycardia or tachycardia which occur independently of changes in b. p. [blood pressure], respiration or movement. Bradycardia appears after a long latency, persists after the stimulus, is often associated with cardiac arrythmias, is mostly elicited from within the amygdala and its appearance is favored by low stimulus frequencies or an associated afterdischarge. Tachycardia has a brief latency, terminates with the stimulus, is elicited from white matter, and is not influenced by stimulus frequency or afterdischarges. It appears that heart rate as a single parameter of cardiovascular function is independently represented in the amygdaloid region and that the descending pathways for bradycardia and tachycardia differ. The former is probably polysynaptic descending along the "secondary projection" path of Gloor. The latter is relatively paucisynaptic and may be mediated along a temporo-hypothalamic or temporo-tegmental pathway.