The process using embryonic stem cells, which can change into various other types of cells, was successfully carried out by Yoshiki Sasai and Mototsugu Eiraku, of the Riken Center for Developmental Biology in Kobe.

The cortex remained undeveloped, equivalent to that of a fetus, but it's the first time that researchers have ever created brain tissue involving different cell types, rather than single brain cells.

Researchers hope that the process will shed light on the how illnesses like Alzheimer's disease work and how they can be cured, as well as leading to treatments to lessen the aftereffects of strokes.

Findings from the research were published in the online edition of the U.S. journal "Cell Stem Cell" on Thursday.

The researchers placed about 3,000 embryonic stem cells in a culture solution, and had the cells gather together naturally to form a solid, and, after 46 days, a sphere of tissue measuring two millimeters in diameter, with a hollow at its center, was formed.

The self-organized tissue uses four types of neurons in four layers, and is identical to the cerebral cortex of a fetus seven to eight weeks after conception. The researchers confirmed that the neurons formed a network, and the cells were able to activate simultaneously.

An adult cerebral cortex has six layers. Accordingly, the stage of development of the cortex in the experiment could be presumed to be at about "40 or 50 percent," Sasai said.