New York, Oct 2 (IANS): A team of US researchers has described how to make an inexpensive, working - but not thinking - miniature brain for drug testing, to test neural tissue transplants or to experiment with how stem cells work in the lab.

The little balls of brain will not perform any cogitation but can produce electrical signals and form their own neural connections -- synapses -- making them readily producible testbeds for neuroscience research, said the researchers from Rhode Island-based Brown University.

"We think of this as a way to have a better in vitro (lab) model that can maybe reduce animal use," said graduate student Molly Boutin.

Just a small sample of living tissue from a single rodent can make thousands of mini-brains.

The recipe involves isolating and concentrating the desired cells with some centrifuge steps and using that refined sample to seed the cell culture in medium in a spherical mold.

The mini-brains, about a third of a millimetre in diametre, are not the first or the most sophisticated working cell cultures of a central nervous system but they require fewer steps to make and they use more readily available materials.

"The materials are easy to get and the mini-brains are simple to make," added co-lead author Yu-Ting Dingle.

The spheres of brain tissue begin to form within a day after the cultures are seeded and have formed complex 3-D neural networks within two to three weeks, the paper shows.

"There are fixed costs, of course, but an approximate cost for each new mini-brain is on the order of $0.25," said study senior author Diane Hoffman-Kim, associate professor of molecular pharmacology.

She hopes the mini-brains might proliferate to many different labs, including those of researchers who have questions about neural tissue.

The paper appeared in the journal Tissue Engineering: Part C.