The brain in the dish, or as the scientists prefer to call it, the ""biologically relevant neural model," is a computer chip with an array of 60 microelectrodes that measure the action potential of neurons grown on top. The microelectrode array, or MEA, records the brain cell signals so the scientists can analyze them.
"The beauty of the MEA is that it doesn't just tell you the activity of one neuron, it tells you the activity of hundreds at the same time," DeMarse said. Using MEAs is not new -- DeMarse used one in 2004 to show that brain cells could be used to control a flight simulator -- but adding adult stem cells to the mix in vitro, that is, in an experiment outside the brain, is the new part.
First, they put cells from an embryonic rat brain in the dish. Those neurons began firing and gradually started "talking" to one another. After about a month, the cells generated stable activity patterns, bursting in unison.
At that point the scientists added neural progenitors -- adult stem cells -- to the network in the dish, which hadn't been done before. The adult stem cells were harvested from rats and were tagged with green fluorescent proteins so they could be distinguished from the original cells in the dish. Neural progenitors are a promising strategy because they can only make brain cells and aren't going to turn into eyeballs or toenails, Ormerod said.