Microbial neuroscience: The gut microbiota as a cognitive layer.

Cognition is traditionally viewed as a brain-centred process, with gut microbes treated primarily as modulators of physiology and behaviour. Recent advances in microbiome research suggest that microbial communities can exhibit history-dependent functional states, adapt their outputs, and dynamically interact with neural systems. This opinion article proposes a distributed model of cognition in which the gut microbiota acts as an intermediate information-processing layer that may influence cognitive states through memory-like persistence and closed-loop feedback with the brain. By integrating concepts from systems neuroscience, microbiology, and cognitive theory, this framework reframes the microbiota as a potential functional contributor to cognition and outlines experimental approaches for testing causal microbiota-gut-brain interactions in behaviour and decision-making.