Influence of anterior midcingulate cortex on drinking behavior during thirst and following satiation.
In humans, activity in the anterior midcingulate cortex (aMCC) is associated with both subjective thirst and swallowing. This region is therefore likely to play a prominent role in the regulation of drinking in response to dehydration. Using functional MRI, we investigated this possibility during a period of "drinking behavior" represented by a conjunction of preswallow and swallowing events. These events were examined in the context of a thirsty condition and an "oversated" condition, the latter induced by compliant ingestion of excess fluid. Brain regions associated with swallowing showed increased activity for drinking behavior in the thirsty condition relative to the oversated condition. These regions included the cingulate cortex, premotor areas, primary sensorimotor cortices, the parietal operculum, and the supplementary motor area. Psychophysical interaction analyses revealed increased functional connectivity between the same regions and the aMCC during drinking behavior in the thirsty condition. Functional connectivity during drinking behavior was also greater for the thirsty condition relative to the oversated condition between the aMCC and two subcortical regions, the cerebellum and the rostroventral medulla, the latter containing nuclei responsible for the swallowing reflex. Finally, during drinking behavior in the oversated condition, ratings of swallowing effort showed a negative association with functional connectivity between the aMCC and two cortical regions, the sensorimotor cortex and the supramarginal gyrus. The results of this study provide evidence that the aMCC helps facilitate swallowing during a state of thirst and is therefore likely to contribute to the regulation of drinking after dehydration.
Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC 3010, Australia. Monash Biomedical Imaging, Monash University, VIC 3800, Australia; michael.j.farrell@monash.edu ddenton@unimelb.edu.au. Monash Biomedicine Discovery Institute, Monash University, VIC 3800, Australia. Department of Medical Imaging and Radiation Sciences, Monash University, VIC 3800, Australia. Monash Biomedical Imaging, Monash University, VIC 3800, Australia. Australian Research Council Centre of Excellence for Integrative Brain Function, Monash University, VIC 3800, Australia. Monash Institute of Clinical and Cognitive Neurosciences, Monash University, VIC 3800, Australia. Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC 3010, Australia. Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia. Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC 3010, Australia; michael.j.farrell@monash.edu ddenton@unimelb.edu.au. Office of the Dean, Faculty of Medicine, Dentistry & Health Sciences, University of Melbourne, Parkville, VIC 3010, Australia. Baker International Diabetes Institute Heart and Diabetes Institute, Melbourne, VIC 3004, Australia.
