Human Cells Make Mice Smarter – Scientific American

these human astrocytes accomplished calcium signaling at least three times faster than the mouse astrocytes did. The enhanced mice masterfully memorized new objects, swiftly learned to link certain sounds or situations to an unpleasant foot shock, and displayed un-usually savvy maze navigationsigns of mental acuity that surpassed skills exhibited by either typical mice or mice transplanted with glial progenitor cells from their own species.”
https://www.scientificamerican.com/article.cfm?id=human-cells-make-mice-smarter