Thalamocortical Mechanisms for Nostalgia-Induced Analgesia.

As a predominately positive emotion, nostalgia serves various adaptive functions, including a recently revealed analgesic effect. The current fMRI study aimed to explore the neural mechanisms underlying the nostalgia-induced analgesic effect on noxious thermal stimuli of different intensities. Human participants' (males and females) behavior results showed that the nostalgia paradigm significantly reduced participants' perception of pain, particularly at low pain intensities. fMRI analysis revealed that analgesia was related to decreased brain activity in pain-related brain regions, including the lingual and parahippocampal gyrus. Notably, anterior thalamic activation during the nostalgia stage predicted posterior parietal thalamus activation during the pain stage, suggesting that the thalamus might play a key role as a central functional linkage in the analgesic effect. Moreover, while thalamus-PAG functional connectivity was found to be related to nostalgic strength, periaqueductal gray-dorsolateral prefrontal cortex (PAG-dlPFC) functional connectivity was found to be associated with pain perception, suggesting possible analgesic modulatory pathways. These findings demonstrate the analgesic effect of nostalgia and, more importantly, shed light on its neural mechanism.SIGNIFICANCE STATEMENT Nostalgia is known to reduce individuals' perception of physical pain. The underlying brain mechanisms, however, are unclear. Our study found that the thalamus plays a key role as a functional linkage between nostalgia and pain, suggesting a possible analgesic modulatory mechanism of nostalgia. These findings have implications for the underlying brain mechanisms of psychological analgesia.