The study:
Probiotic Bifidobacterium longum BB68S Improves Cognitive Functions in Healthy Older Adults: A Randomized, Double-Blind, Placebo-Controlled Trial
“After BB68S intervention, the relative abundances of Solobacterium and Oribacterium decreased significantly (Figure 5C).”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9824790/
What probiotics have it (from Amazon and elsewhere):
Life Extension Bifido GI Balance - Probiotics Bifidobacterium Longum BB536 (2 Billion CFU) Supplement – Support Healthy Gut & Digestive Health – Gluten-Free, Vegetarian – 60 Capsules
Supersmart - Bifidobacterium Longum (BB536) 6 Billion CFU per Day - Probiotics & Prebiotics Supplement
Vitamatic Bifidobacterium Longum Probiotic Powder - Digestive Health Support - 100 Gram (3.5 OZ) - 100 Servings (100 Billion a scoop)
I apologize. I was looking for the specific study strain, but the search engine brought up a slightly different substrain.
To be fair, both likely work similarly, but, technically, it is a close relative to the one listed in the study I put in post #11.