Donders Centre for Brain, Cognition and Behaviour, Radboud University Nijmegen, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands.
Physiol Behav. 2012 Feb 1;105(3):607-12. doi: 10.1016/j.physbeh.2011.09.018. Epub 2011 Sep 28.
The current study reports on a number of heart rate responses observed in rats subjected to a discriminatory Pavlovian fear conditioning procedure. Rats learned that a series of six auditory pips was followed by a footshock when presented alone, but not when the pip series was preceded by a visual safety signal. Each auditory pip in the series evoked a fast transient (<1s) cardiac deceleration. This was the case on both trials followed by shock and on trials not followed by shock. The onset of the safety light evoked a similar fast deceleration. We propose that these transient decelerations are similar to the human Evoked Cardiac Response 1 (ECR1), a brief modest deceleration evoked by simple sensory stimuli that is thought to reflect an early process of stimulus registration. Immediately following these pip-evoked decelerations, modest fast accelerations were observed. These accelerations were larger when the pip series was followed by shock than when it was not followed by shock. We propose a potential linkage between these accelerations and the human acceleratory ECR2 component, which is associated with more elaborate processing following stimulus registration; something likely to take place when the pip series predicts an aversive event. Both the ECR1- and ECR2-like responses were embedded within a slow, gradual heart rate increase across the entire pip series. This tonic increase was significantly larger on trials with footshock and is therefore probably associated with anticipatory fear of the upcoming shock. An additional special type of cardiac response was found to the first pip in the series not preceded by the safety signal; here, a much larger and more sustained deceleration was apparent. This response appears relatable to the prolonged deceleration reported in humans in response to aversive picture content. We discuss the cardiac responses found in rats in the current study in the context of heart rate responses known in the human literature.
本研究报告了在接受辨别性巴甫洛夫恐惧条件反射程序的大鼠中观察到的一些心率反应。大鼠学会了当单独呈现时，一系列六个听觉音调和随后的电击，但当音调和系列之前出现视觉安全信号时则不会。该系列中的每个听觉音调都会引起快速瞬态（<1 秒）的心率减速。无论是在跟随电击的试验中还是在未跟随电击的试验中都是如此。安全灯的开启也会引起类似的快速减速。我们提出，这些短暂的减速类似于人类的诱发心脏反应 1（ECR1），这是一种由简单感觉刺激引起的短暂适度减速，被认为反映了刺激注册的早期过程。在这些音调引起的减速之后，会观察到适度的快速加速。当音调和系列跟随电击时，这些加速会更大。当音调和系列不跟随电击时，这些加速会更大。我们提出了这些加速度与人类加速度 ECR2 成分之间的潜在联系，ECR2 成分与刺激注册后的更精细的处理有关；当音调和系列预测不愉快的事件时，可能会发生这种情况。ECR1 和 ECR2 样反应都嵌入在整个音调和系列中的缓慢、逐渐的心率增加中。在有电击的试验中，这种紧张性增加明显更大，因此可能与对即将到来的电击的预期恐惧有关。还发现了与第一个音调和系列没有安全信号的音调有关的特殊类型的心脏反应；在这里，明显会出现更大且更持久的减速。这种反应似乎与人类在应对不愉快的图片内容时报告的延长减速有关。我们在人类文献中已知的心率反应背景下讨论了当前研究中大鼠的心脏反应。
