264 contributions to learned nocebo effects. As discussed below, our findings add some level of detail to the existing literature, by focusing in on specific cognitive and emotional mechanisms, beyond the usual focus on the broader concept of associative learning. To understand some of the features of nocebo hyperalgesia that the current behavioral and neuroimaging literature does not tackle, we designed and carried out a series of experimental studies on learned nocebo effects. Chapter 4 indicates that, when replicating a clinically relevant context on ambiguous and inconsistent learning, nocebo effects can still be induced. In the continuous reinforcement group of this study we used a typical nocebo paradigm, comparable to many previous studies 109–11120–24. But using a second group, we also set out to reproduce results from a prior study 24 that utilized partially reinforced learning. Our objective was achieved; we showed that next to a typical nocebo paradigm (that is shown to dependably induce a nocebo effect in chapter 2), a more ambiguous and ecologically valid learning method is still able to induce a hyperalgesic effect, at least to some extent. Not only is this realistic type of learning sufficient to alter the experience of pain, but ambiguity may add strength to learning so that nocebo effects can withstand attenuation over time. This was an important building block in our understanding of pain chronification from the lens of nocebo hyperalgesia. Our chapter 4 results were in line with some initial studies that have indicated that nocebo effects may rely upon especially durable learned associations that resist attenuation 23–25. When attempting to attenuate the induced effects, we observed that continuously reinforced, reliable nocebo associations were easier to reverse, whereas ambiguous, partially reinforced learning led to significant resistance to attenuation. We confirmed that ambiguous and variable learning can lead to hyperalgesic effects, and additionally showed that these variable associations persist over time, even after active countering of such a negative association. It appears that negative
RkJQdWJsaXNoZXIy MTk4NDMw