96 indicated that differential electrophysiological processes characterize learned expectation of analgesia and hyperalgesia. In sum, EEG and MEG studies provide support that learning is involved in nocebo hyperalgesia, while also highlighting the role of pain processing, at the electrophysiological level. It is worth noting that the role of regions such as the amygdala and the hippocampus, that are perhaps best summarized in the context of (affective) learning, highlight the more refined and specific aspects of learning that underlie nocebo hyperalgesia. Many of the aforementioned relevant brain areas point towards integrative learning mechanisms being involved in nocebo hyperalgesia, including, for instance, the ACC and dlPFC. While it is generally accepted that learning plays a key role in nocebo hyperalgesia 4,103,104, unravelling the more exact learning correlates that contribute to the formation of nocebo effects is imperative. The amygdala and the hippocampus have specifically been implicated in aversive learning and conditions such as phobias, where fear learning plays a crucial role 105–107. The role that the hippocampus plays in nocebo hyperalgesia 19,59 relates to previous findings that the hippocampus mediates aversive learning 108. This may in turn highlight an involvement of aversive learning processes in nocebo hyperalgesia. Moreover, within brain networks that include the ACC 18,63, expectations and pain processing may be integrated in a way that involves the evaluation of sensory information based on learned negative expectations. In collaboration with the dlPFC, brain regions such as the ACC and the somatosensory cortex integrate information 109 and are reportedly involved in expectation, anticipation, and error processing 89,110, which are also essential elements of associative learning processes. At the same time, electrophysiological findings described in this review connect nocebo hyperalgesia to long-term learning processes 5,15 as well as brain plasticity, with subcortical alpha-band oscillations engaging in rhythmic activities that have a plasticity function 111. These findings provide supporting physiological evidence of learning via association
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