Neural correlates of the emergence of consciousness of thirst.
Gary Egan, Tim Silk, Frank Zamarripa, John Williams, Paolo Federico, Ross Cunnington, Leonie Carabott, John Blair-West, Robert Shade, Michael McKinley, Michael Farrell, Jack Lancaster, Graeme Jackson, Peter Fox, Derek Denton
Proceedings of the National Academy of Sciences of the United States of America December 9, 2003 DOI: 10.1073/pnas.2136650100 (opens in new tab) via PubMed
Summary
AI-generated from the abstractThirst was induced in humans by intravenous infusion of hypertonic saline. PET imaging revealed blood flow changes in ancient brain regions similar to those seen when thirst is maximal, while fMRI additionally showed activation in the anterior wall of the third ventricle, a region central to thirst generation in animals. Strong fMRI activations also appeared in the anterior cingulate, parahippocampal gyrus, frontal gyri, insula, and cerebellum. Drinking water to satiation immediately reduced thirst and caused a sharp decline in anterior cingulate activation, but the third ventricle activation remained unchanged, consistent with the time needed for plasma sodium to change after water absorption.
Study at a glance
| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 14 |
| Population | Humans |
| Dose | 0.51 M at 13.4 ml/min |
| Key finding | fMRI revealed activation in the anterior wall of the third ventricle during induced thirst, a region not detected by PET, and drinking water to satiation caused a precipitate decline in anterior cingulate activation while third ventricle activation remained unchanged. |
Abstract
Thirst was induced by rapid i.v. infusion of hypertonic saline (0.51 M at 13.4 ml/min). Ten humans were neuroimaged by positron-emission tomography (PET) and four by functional MRI (fMRI). PET images were made 25 min after beginning infusion, when the sensation of thirst began to enter the stream of consciousness. The fMRI images were made when the maximum rate of increase of thirst occurred. The PET results showed regional cerebral blood flow changes similar to those delineated when thirst was maximal. These loci involved the phylogenetically ancient areas of the brain. fMRI showed activation in the anterior wall of the third ventricle, an area that is key in the genesis of thirst but is not an area revealed by PET imaging. Thus, this region plays as major a role in thirst for humans as for animals. Strong activations in the brain with fMRI included the anterior cingulate, parahippocampal gyrus, inferior and middle frontal gyri, insula, and cerebellum. When the subjects drank water to satiation, thirst declined immediately to baseline. A precipitate decline in intensity of activation signal occurred in the anterior cingulate area (Brodmann area 32) putatively related to consciousness of thirst. The intensity of activation in the anterior wall of the third ventricle was essentially unchanged, which is consistent with the fact that a significant time (15-20 min) would be needed before plasma Na concentration changed as a result of water absorption from the gut.