Ben-Jacob and his fellow boffins apparently mounted their artificially-cultured brain tissue on "a polymer panel studded with electrodes." (Won't be long before they start using full-size brains in jars of bubbling transparent fluid, we reckon.) The scientists then injected the hapless culture with "picrotoxin, a cocktail of gamma-aminobutyric acid (GABA)."
Apparently, "the cells on the electrode array came from the cortex, the outermost layer of the brain known for its role in memory formation," though it wasn't clear whose cortex or how they got the slime out of the donor's head.
The injection of picrotoxic gamma acid enabled the neurons, essentially, to start behaving persistently in an organised way - or to put it another way, BROUGHT A DEAD BRAIN TO LIFE.