Tiny replicas of the human brain have been created by John Hopkins researchers to study the neurological diseases and conduct experimental drug testing, replacing the many animals currently being used for neurological scientific research.
The miniature brains are about the size of a common housefly, which contains neurons and cells of a human brain and even shows evidence of electrical activity that can be measured.
A scientist at Johns Hopkins in the US says they can be mass-produced in labs to allow new drugs to be tested for safety and effectiveness without the need for animals which often do not mirror how human cells work.
"While rodent models have been useful, we are not 150-pound rats. And even though we are not balls of cells either, you can often get much better information from these balls of cells than from rodents. We believe that the future of brain research will include less reliance on animals, more reliance on human, cell-based models."
Dr Hartung said the brains had even started to produce 'a primitive type of thinking.' "Obviously, there's no input or output," he added. "It is meaningless electrical activity but the neurons are trying to communicate with each other."
The miniature brains are made from skin cells of adults which have been reprogrammed back to a stem-cell-like state, then grown into brain cells, which then transform into mini-brains within eight weeks.
The research team also said that the cells from people with certain genetic traits could also be grown to provide a model for diseases like Alzheimer's, Parkinson's or multiple sclerosis.
"It also has the beauty that we can do this from essentially anybody," added Dr Hartung.
"We have been doing this from five different donors so far, among them also people with genetic diseases. So we can test for the first time the combination of genetic traits together with the effect of substances, because many diseases are not explained by genes along."
"We have been doing work on Parkinson's as an example, which we're publishing because we can really replicate some of the hallmarks of Parkinson's in human brain model."
The electrophysiological activity of the brain was recorded with electrodes. The researchers placed a miniature brain on an array of electrodes and listened to the spontaneous electrical communication of the neurons as test drugs were added.
The research was presented at the annual Advancement for American Science Annual Conference (AAAS) in Washington.