Beyond the 'second brain': the gut microbiota as a constitutive co-constructor of embodied cognitive network.
Frontiers in neuroscience January 1, 2026 Yue Gou, Xuemei Liu, Wenjie Zhu et al. 1 citation
Cognition, emotion, and behavior arise from ongoing bidirectional communication between a host and its symbiotic gut microbes, not from brain-isolated processes alone. The gut microbiota acts as an embedded signaling system, producing cognitively active metabolites like short-chain fatty acids and neuroactive substances that shape interoceptive states and neural function through neural, immune, and metabolic pathways. Evidence from germ-free animal models, fecal microbiota transplantation, human multi-omics, and clinical interventions indicates that microbiota-derived processes are constitutively relevant to embodied cognitive architectures organized by interoceptive prediction, affective appraisal, and vagal-metabolic signaling. This framework moves beyond a linear gut-brain axis to a multispecies model, offering a biological foundation for the mind and enabling precision mental health interventions like psychobiotics.