Abstract

The complexity of the human mind and its interaction with the environment is one of the main epistemological debates throughout history. Recent ideas, framed as the 4E perspective to cognition, highlight that human experience depends causally on both cere- bral and extracranial processes, but also is embedded in a particular sociomaterial con- text and is a product of historical accumulation of trajectory changes throughout life. Accordingly, the human microbiome is one of the most intriguing actors modulating brain function and physiology. Here, we present the 4E approach to the Human Micro- biome for understanding mental processes from a broader perspective, encompassing one’s body physiology and environment throughout their lifespan, interconnected by microbiome community structure and dynamics. We review evidence supporting the approach theoretically and motivates the study of the global set of microbial ecosys- tem networks encountered by a person across their lifetime (from skin to gut to nat- ural and built environments). We furthermore trace future empirical implementation of the approach. We finally discuss novel research opportunities and clinical interven- tions aimed toward developing low-cost/high-benefit integrative and personalized bio- psycho-socio-environmental treatments for mental health and including the brain-gut- microbiome axis.