The SERNA Conceptual Standard for Gut-Brain Axis and Neuro-Behavioral Regulation: Definitions, Relationships, and Theoretical Integration (SCS-GBA)

The bidirectional communication between the gastrointestinal tract and the central nervous system—the Gut-Brain Axis (GBA)—is one of the most rapidly evolving frontiers in neuroscience and psychiatry. Despite its promise, the field is characterized by significant terminological fragmentation regarding the role of the microbiome, the vagus nerve, and the neuro-immune system. Researchers frequently conflate "microbiota composition" with "microbiome function," and the causal pathways between gut dysbiosis and behavioral dysregulation are often poorly defined. This document presents the SERNA Conceptual Standard for Gut-Brain Axis and Neuro-Behavioral Regulation (SCS53), a unified theoretical framework designed to standardize definitions and model the causal pathways of microbiota-to-brain signaling. SCS53 establishes 12 canonical terms (SCS53-T01 through T12) that strictly differentiate between vagal, endocrine, and immune-mediated signaling. The standard introduces the Microbial-Neuro-Affective (MNA) model, which incorporates 10 testable hypotheses (SCS53-H01 through H10) mapping the bi-directional relationships between the gut microbiome, intestinal permeability, and the limbic system. By resolving 8 documented field inconsistencies—such as the "Direct vs. Indirect" vagal signaling debate—SCS53 provides a rigorous foundation for cumulative science in psychobiotics and nutritional neuroscience.