Neural correlates of the emergence of consciousness of thirst

Abstract

Thirst was induced by rapid i.v. infusion of hypertonic saline (0.51 M at 13.4 ml͞min). 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.

Cerebellar Vermis Involvement in Cocaine-Related Behaviors

“…Vermis activation also occurs in response to nondrug rewards or their anticipation (Rogers et al, 1999;Kunig et al, 2000;Martin-Solch et al, 2001;Knutson et al, 2003), painful or aversive stimuli or their anticipation (Paradiso et al, 1999;Casey et al, 2000;Becerra et al, 2001), and interoceptive stimuli triggered by vegetative regulatory functions including thirst (Egan et al, 2003), hunger (Tataranni et al, 1999), and respiratory stress (Evans et al, 2002). Together, those findings are consistent with the suggestion that the cerebellum and the vermis process multimodal sensory inputs to influence cortical excitability and enhance motor sequence learning and execution (Molinari et al, 2002).…”

Unique, common, and interacting cortical correlates of thirst and pain

“…In addition to the cingulate and insula, the maximum thirst contrast identified activity in the frontal, temporal, and occipital cortices. We have previously reported frontal and temporal activity for moderate thirst, whereas activity in the cuneus was confined to the experience of mild thirst (1,11). The extensive activity in the medial frontal gyrus and paracentral lobule is a novel finding for the maximum thirst contrast, although this area was beyond the field of view in the earlier report (1).…”

“…A statistical parametric map of the pain response was generated by contrasting noxious pressure (scans 2, 4, 9, and 10) with no pressure (scans 1, 3, 8, and 11). A maximum thirst statistical parametric map was generated by contrasting the baseline (scans 1-4) with maximum thirst (scans [8][9][10][11]. Interactions between pain and maximum thirst were tested by contrasting concurrent pain and thirst (scans 9 and 10) with maximum thirst (scans 8 and 11) and pain (scans 2 and 4) in isolation.…”

“…Studies of thirst-related brain activity have identified a network including the hypothalamus, thalamus, insula, parahippocampus, somatosensory cortex, anterior cingulate, posterior cingulate, and cerebellum (1,(10)(11)(12). A metaanalysis of pain imaging studies revealed a consistent network incorporating activity in the diencephalon and posterior parietal, insula, and limbic cortices and cerebellum (13).…”

Effect of aging on regional cerebral blood flow responses associated with osmotic thirst and its satiation by water drinking: A PET study

“…that enhance activation of the neural systems that are the neural correlates of the subjective state termed thirst. The rise in osmolality and advent of thirst is associated with activations in the hypothalamus, thalamus, limbic cortex, somatosensory cortex, insula, and cerebellum (12)(13)(14). Of the regions so activated, the cingulate cortex appears to be particularly important, being rapidly responsive to satiation of thirst as indicated by neuroimaging changes.…”