The human gastrointestinal tract (GIT) is inhabited by a wide cluster of microorganisms that play protective, structural, and metabolic functions for the intestinal mucosa. Gut microbiota is involved in the barrier functions and in the maintenance of its homeostasis. It provides nutrients, participates in the signaling network, regulates the epithelial development, and affects the immune system. Considering the microbiota ability to respond to homeostatic and physiological changes, some researchers proposed that it can be seen as an endocrine organ. Evidence suggests that different factors can determine changes in the gut microbiota. These changes can be both quantitative and qualitative resulting in variations of the composition and metabolic activity of the gut microbiota which, in turn, can affect health and different disease processes. Recent studies suggest that exercise can enhance the number of beneficial microbial species, enrich the microflora diversity, and improve the development of commensal bacteria. All these effects are beneficial for the host, improving its health status. In this paper, we intend to shed some light over the recent knowledge of the role played by exercise as an environmental factor in determining changes in microbial composition and how these effects could provide benefits to health and disease prevention.

The basal forebrain cholinergic system is considered as a major component of attentive mediator system. It could be activated by different ingoing inputs, and among them the hypothalamus represents an important source of projections and the orexin neurons, whose cell bodies are present in the lateral hypothalamus, highly contribute to these projections. Recently, the orexin-producing neurons have been considered to act in the basal forebrain promoting arousal and attention. Aim of the present review is trying to explain the putative effects of orexin-producing neurons and their projection to the basal forebrain in order to support the hypothesis that orexin system may contribute to attentional processing toward increased cell activity and cortical acetylcholine (Ach) release. Collectively, the available data seem to support this hypothesis: orexins excite cholinergic neurons increasing acetylcholine release in cerebral cortex contributing to cerebral cortical activation and prefrontal cortex associated with executive system. We have reviewed evidence suggesting that the BF may be a key target through which orexin neurons promote attention.