20,21 Indeed, the cerebral blood flow rates and velocities are increased during the withdrawal state, mainly in high users20,26 and go back to baseline values after about 2 h.26 Therefore the widespread lack of significance in the perfusion values recorded in the present study with and without caffeine may partly reflect the withdrawal state induced by the overnight Inhibitors,research,lifescience,medical caffeine deprivation imposed on the subjects. On the other hand, the discrete changes recorded in some brain areas after caffeine indicate the specific changes

due to the methylxanthine. In the present study, on a background of widespread statistically nonsignificant perfusion decrease, discrete increases Inhibitors,research,lifescience,medical in perfusion corresponding to specific neuronal activation could be identified. Brain activation was mostly seen in the LC group. In this group, significant activation was recorded in regions known to mediate anxiety like the inferior frontal gyrus-anterior Fostamatinib nmr insular cortex, the uncus, the lingual gyrus, and the cerebellum.27,28 Simultaneously, many other regions involved in the regulation of anxiety levels, such as the amygdala, cingulate and orbitofrontal

cortex, thalamus, and striatum, were not activated by caffeine. The inferior frontal gyrus-anterior insular Inhibitors,research,lifescience,medical cortex seems to play a role in anticipating aversive stimuli and in anxiety and emotion regulation.29 Its activation Inhibitors,research,lifescience,medical was observed in different anticipatory anxiety induction protocols,30-32 and was totally different from the claustrum-posterior insular cortex activation observed in pharmacologically induced panic attacks

with cardiovascular and visceral symptomatology32-34 Caffeine is known to be anxiogenic, at low doses in a subset of individuals and at quite large doses in most of the population.35 The activation recorded only in a limited Inhibitors,research,lifescience,medical number of areas may reflect the fact that the subjects did not report increased anxiety after ingestion of the caffeinated drink. They could also imply that caffeine may specifically act at some given steps of the anxiety process, for example, at the anterior insular cortex for integration of internal state, parietal cortex for spatially specific associations, but does not reach, at through this dose, the sensory-motor integration in thalamus and the initiation of action – since there is no defensive action required – depending on the anterior cingulate cortex.28,36 Brain activation was observed in the internal parietal cortex of LC subjects and in the hypothalamus of HC subjects. These activations relate to changes in vigilance and attention. The parietal cortex is critical for attention and spatial updating. It is involved in visual representations of space in an eye-centered coordinate frame, and in providing a signal for directing the eyes towards these objects.28,37 The hypothalamus mediates many vegetative functions as well as attention and vigilance.