The mechanism by which HA impairs cognitive function is beginning to be clarified in animal studies. Portacaval shunts (PCS) rats have been found to develop learning im- pairment of the Y-maze task. These rats exhibit HA and neuroinflammation [36]. Treatment of PCS rats with the anti-inflammatory, ibuprofen, reduces neuroinflammation but not HA, and also restores learning ability [38]. Fur- thermore, data from a rat model of chronic HA have sug- gested that neuroinflammation mediates the deleterious ef- fects of HA on cognitive function [1]. These results suggest that HA may induce neuroinflammation-mediated cognitive impairment. In support of this pathogenic role, our study shows that HA induces neuroinflammation in the cerebel- lum, hippocampus and prefrontal cortex, and impairs learn- ing ability and spatial memory in rats. Therefore, probiotic treatment may be beneficial for HA-mediated cognitive decline in rats given because cognitive decline is improved and neuroinflammation is attenuated with this treatment.