In conclusion, the data from our study suggest that administration of probiotic L. helveticus strain NS8 is a poten- tial therapeutic approach for HA-mediated cognitive decline and anxiety-like behavior. The effect of probiotic treatment on improving behaviors may be attributed to its immuno- modulatory properties of attenuating neuroinflammation and reducing 5-HT metabolism. We therefore provide strong evidence supporting the possible use of probiotic treatment for neurological disorders in addition to its use in the gastrointestinal tract. A better understanding of the be- havioral effect of probiotics would require further investiga- tions of their immunomodulatory activity.