Microbial modulators of the mind: probiotic interventions in hippocampal neurogenesis and cognitive flexibility

The gut-brain axis serves as a foundational communication channel between the intestinal microbiome and the brain, facilitating microbial impact on neural functions. Probiotics, defined as health-promoting live microorganisms, are being increasingly investigated for their regulatory effects on neuroplasticity and mental acuity. Recent evidence suggests that probiotics modulate hippocampal neurogenesis, a crucial process underlying learning, memory, and cognitive flexibility. Through the suppression of pro-inflammatory mechanisms, enhancement of neurotrophic factor biosynthesis, alleviation of oxidative burden, and stabilization of HPA axis function, probiotics contribute to sustaining hippocampal neural resilience and promoting synaptic adaptability. Evidence from both preclinical experiments and clinical evaluations suggests that strains like Lactobacillus rhamnosus, Bifidobacterium longum, and Lactobacillus plantarum may play a beneficial role in promoting adaptive cognitive functioning. These benefits are thought to be mediated via increased expression of brain-derived neurotrophic factor, modulation of microglial activation, and alteration of neurotransmitter metabolism including serotonin, dopamine, and GABA. This review synthesizes current findings on the molecular and cellular pathways through which probiotics support hippocampal neurogenesis and cognitive flexibility, and discusses their potential as a non-invasive, adjuvant strategy for cognitive enhancement in neurological disorders and age-related cognitive decline.