Brainstem functional connectivity integrates microbiome-gut-brain signals in healthy older adults: a cross-sectional evaluation and a randomised controlled probiotic trial

In healthy adults aged 60–80, resting brainstem functional connectivity links age, stress, mood, and cognition to specific brainstem–cortex pathways, and probiotic intake alters locus coeruleus connectivity.

• Why it matters: The gut-brain axis is widely studied, but how autonomic and brainstem networks participate in human gut-brain signalling during healthy ageing is unclear.
• What they did: The study measured brainstem-optimised resting-state fMRI connectivity before and after a six-week randomized, double-blinded, placebo-controlled trial of Lacticaseibacillus rhamnosus HN001 in non-encapsulated and microencapsulated forms.
• The result: Baseline age, stress, mood, and cognitive status correlated with connectivity patterns (all p<0.0063), and probiotic intervention showed time*group effects for locus coeruleus and ventral tegmental area, with within-group changes for non-encapsulated but no between-group differences (all p<0.0056).

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