The cardiac defense response (CDR) to intense auditory stimulation is characterized by two acceleration-deceleration heart rate (HR) components. This study investigated contributions of sympathetic cardiac control to habituation and recovery of the CDR. Fifty-six healthy subjects were presented with noise stimuli eliciting the CDR. Three stimuli were presented with short and long (2.5 min and 12.5 min) inter-trial intervals (ITIs). The pre-ejection period was recorded as an index of sympathetic cardiac control, in addition to HR. Repeated stimulation at short ITI was associated with marked habituation of the HR and sympathetic responses; both responses exhibited a degree of recovery with long ITI. Regarding the time course, the first acceleration-deceleration was accompanied by a decline and subsequent increase in sympathetic cardiac control. During the second acceleration-deceleration, the parameters exhibited parallel courses. These results suggest that the sympathetic contribution to the habituation and recovery is limited to the second HR component.

中文翻译：

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对心脏防御反应的习惯和恢复的同情贡献

对强烈听觉刺激的心脏防御反应 (CDR) 的特点是两个加速-减速心率 (HR) 分量。本研究调查了交感神经心脏控制对 CDR 的适应和恢复的贡献。向 56 名健康受试者提供引起 CDR 的噪声刺激。三个刺激以短和长（2.5 分钟和 12.5 分钟）的试验间间隔 (ITI) 呈现。除 HR 外，射血前期还被记录为交感神经心脏控制的指标。短时间 ITI 的重复刺激与 HR 和交感神经反应的显着习惯有关；两种反应都表现出一定程度的恢复，并且 ITI 时间较长。关于时间过程，第一次加速-减速伴随着交感神经心脏控制的下降和随后的增加。在第二次加减速过程中，参数表现出平行轨迹。这些结果表明，对习惯化和恢复的同情贡献仅限于第二个 HR 组件。