Regional brain responses associated with drinking water during thirst and after its satiation.
The instinct of thirst was a cardinal element in the successful colonization by vertebrates of the dry land of the planet, which began in the Ordovician period about 400 million y ago. It is a commonplace experience in humans that drinking water in response to thirst following fluid loss is a pleasant experience. However, continuing to drink water once thirst has been satiated becomes unpleasant and, eventually, quite aversive. Functional MRI experiments reported here show pleasantness of drinking is associated with activation in the anterior cingulate cortex (Brodmann area 32) and the orbitofrontal cortex. The unpleasantness and aversion of overdrinking is associated with activation in the midcingulate cortex, insula, amygdala, and periaqueductal gray. Drinking activations in the putamen and cerebellum also correlated with the unpleasantness of water, and the motor cortex showed increased activation during overdrinking compared with drinking during thirst. These activations in motor regions may possibly reflect volitional effort to conduct compliant drinking in the face of regulatory mechanisms inhibiting intake. The results suggestive of a specific inhibitory system in the control of drinking are unique.
Department of Anatomy and Neuroscience, Department of Physiology, Office of the Dean, Faculty of Medicine, Dentistry, and Health Sciences, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC 3010, Australia.
Pascal
P
Saker
Michael J
MJ
Farrell
Faiz R M
FR
Adib
Gary F
GF
Egan
Michael J
MJ
McKinley
Derek A
DA
Denton
D000328:Adult; D001921:Brain / Q000502:physiology*; D060766:Drinking Water; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013894:Thirst; D055815:Young Adult
D060766:Drinking Water
fMRI; swallowing