An almost complete version of a tiny human brain has been grown in a US lab in a move that could bring major strides to the treatment of neurological diseases, a scientist says.

Rene Anand, a professor at Ohio State University, has grown in a dish a brain equal in maturity to that of a five-week-old fetus, his university reported.

"It not only looks like the developing brain, its diverse cell types express nearly all genes like a brain," Anand said.

Around the size of a pea, the brain in a lab dish includes multiple cell types, all major regions of the brain and a spinal cord, but lacks a vascular system, the university said.

It was grown from human skin cells and is claimed to be the most complete brain of its type grown yet.

Anand presented his research at a military health event in Florida on Tuesday.

Major scientific advances are usually published in peer-reviewed journals, where the claims are assessed independently before they are made public.

Anand and a colleague have co-founded an Ohio start-up company to commercialize the brain growth system, according to the university.

Anand expects the grown brain will allow easier and more ethical testing of drugs' effects on the mind, as scientists seek cures for brain disease and nervous system disorders, the school said.

"The power of this brain model bodes very well for human health because it gives us better and more relevant options to test and develop therapeutics other than rodents," Anand said in a university report on his research.

It could also be a boon for general neuroscience research as the brain allows a hands-on approach to genome studies rather than computer models currently used.

"Mathematical correlations and statistical methods are insufficient to in themselves identify causation. You need an experimental system –- you need a human brain," he said.