Andreatta Marta, Pauli Paul
Department of Psychology (Biological Psychology, Clinical Psychology, and Psychotherapy), University of Würzburg Würzburg, Germany.
Front Behav Neurosci. 2015 May 19;9:128. doi: 10.3389/fnbeh.2015.00128. eCollection 2015.
In classical conditioning, an initially neutral stimulus (conditioned stimulus, CS) becomes associated with a biologically salient event (unconditioned stimulus, US), which might be pain (aversive conditioning) or food (appetitive conditioning). After a few associations, the CS is able to initiate either defensive or consummatory responses, respectively. Contrary to aversive conditioning, appetitive conditioning is rarely investigated in humans, although its importance for normal and pathological behaviors (e.g., obesity, addiction) is undeniable. The present study intents to translate animal findings on appetitive conditioning to humans using food as an US. Thirty-three participants were investigated between 8 and 10 am without breakfast in order to assure that they felt hungry. During two acquisition phases, one geometrical shape (avCS+) predicted an aversive US (painful electric shock), another shape (appCS+) predicted an appetitive US (chocolate or salty pretzel according to the participants' preference), and a third shape (CS-) predicted neither US. In a extinction phase, these three shapes plus a novel shape (NEW) were presented again without US delivery. Valence and arousal ratings as well as startle and skin conductance (SCR) responses were collected as learning indices. We found successful aversive and appetitive conditioning. On the one hand, the avCS+ was rated as more negative and more arousing than the CS- and induced startle potentiation and enhanced SCR. On the other hand, the appCS+ was rated more positive than the CS- and induced startle attenuation and larger SCR. In summary, we successfully confirmed animal findings in (hungry) humans by demonstrating appetitive learning and normal aversive learning.
在经典条件反射中，一个最初中性的刺激（条件刺激，CS）与一个具有生物学显著性的事件（无条件刺激，US）建立联系，该事件可能是疼痛（厌恶条件反射）或食物（奖赏性条件反射）。经过几次关联后，CS能够分别引发防御性或 consummatory 反应。与厌恶条件反射相反，奖赏性条件反射在人类中很少被研究，尽管其对正常和病理行为（如肥胖、成瘾）的重要性是不可否认的。本研究旨在将关于奖赏性条件反射的动物研究结果转化到人类身上，使用食物作为无条件刺激。33名参与者在上午8点至10点之间未吃早餐的情况下接受调查，以确保他们感到饥饿。在两个习得阶段，一种几何形状（avCS+）预示着厌恶的无条件刺激（痛苦的电击），另一种形状（appCS+）预示着奖赏性无条件刺激（根据参与者的偏好为巧克力或咸脆饼干），第三种形状（CS-）则不预示任何无条件刺激。在消退阶段，这三种形状加上一种新形状（NEW）再次呈现，且不给予无条件刺激。收集效价和唤醒评分以及惊吓和皮肤电导（SCR）反应作为学习指标。我们发现了成功的厌恶和奖赏性条件反射。一方面，avCS+的评分比CS-更负面、更具唤醒性，并引发惊吓增强和SCR增强。另一方面，appCS+的评分比CS-更积极，并引发惊吓减弱和更大的SCR。总之，我们通过证明奖赏性学习和正常的厌恶学习，成功地在（饥饿的）人类中证实了动物研究结果。
