Hydrogen was found to improve cognitive function in aged mice after surgery. The researchers divided the mice into three groups: one had surgery, one had surgery and received hydrogen-enriched saline, and one had a sham operation. They tested the mice's memory and took blood and brain samples to measure certain proteins. The mice that received hydrogen performed better in memory tests, had lower levels of certain proteins in their blood, and had lower levels of these proteins in their brains compared to the other groups. This suggests that hydrogen may help protect cognitive function in older mice after surgery.