Saker Pascal, Carey Steve, Grohmann Marcus, Farrell Michael J, Ryan Philip J, Egan Gary F, McKinley Michael J, Denton Derek A
Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC 3010, Australia.
Steve Carey Hypnotherapy, Hampton, VIC 3192, Australia.
Proc Natl Acad Sci U S A. 2020 Jun 16;117(24):13750-13756. doi: 10.1073/pnas.2002825117. Epub 2020 Jun 1.
In response to dehydration, humans experience thirst. This subjective state is fundamental to survival as it motivates drinking, which subsequently corrects the fluid deficit. To elicit thirst, previous studies have manipulated blood chemistry to produce a physiological thirst stimulus. In the present study, we investigated whether a physiological stimulus is indeed required for thirst to be experienced. Functional MRI (fMRI) was used to scan fully hydrated participants while they imagined a state of intense thirst and while they imagined drinking to satiate thirst. Subjective ratings of thirst were significantly higher for imagining thirst compared with imagining drinking or baseline, revealing a successful dissociation of thirst from underlying physiology. The imagine thirst condition activated brain regions similar to those reported in previous studies of physiologically evoked thirst, including the anterior midcingulate cortex (aMCC), anterior insula, precentral gyrus, inferior frontal gyrus, middle frontal gyrus, and operculum, indicating a similar neural network underlies both imagined thirst and physiologically evoked thirst. Analogous brain regions were also activated during imagined drinking, suggesting the neural representation of thirst contains a drinking-related component. Finally, the aMCC showed an increase in functional connectivity with the insula during imagined thirst relative to imagined drinking, implying functional connectivity between these two regions is needed before thirst can be experienced. As a result of these findings, this study provides important insight into how the neural representation of subjective thirst is generated and how it subsequently motivates drinking behavior.
为应对脱水，人类会感到口渴。这种主观状态对生存至关重要，因为它促使人们饮水，进而纠正液体不足。为引发口渴，以往的研究通过操控血液化学成分来产生生理性口渴刺激。在本研究中，我们调查了口渴体验是否确实需要生理刺激。功能性磁共振成像（fMRI）用于扫描完全补水的参与者，让他们想象极度口渴的状态以及想象饮水以解渴的状态。与想象饮水或基线状态相比，想象口渴时的主观口渴评分显著更高，这表明口渴与潜在生理状态成功分离。想象口渴状态激活的脑区与先前关于生理性诱发口渴的研究报告的脑区相似，包括前扣带回中部皮质（aMCC）、前岛叶、中央前回、额下回、额中回和岛盖，这表明想象口渴和生理性诱发口渴有着相似的神经网络基础。在想象饮水过程中也激活了类似的脑区，这表明口渴的神经表征包含与饮水相关的成分。最后，相对于想象饮水，在想象口渴时aMCC与岛叶之间的功能连接增加，这意味着在体验到口渴之前，这两个区域之间需要功能连接。基于这些发现，本研究为口渴主观感受的神经表征如何产生以及随后如何激发饮水行为提供了重要见解。
