A type of stem cell key to higher thinking in humans has been discovered by scientists.
Researchers have identified a family of stem cells that may give birth to neurons responsible for abstract thought and creativity.
The cells were found in embryonic mice, where they formed the upper layers of the brain's cerebral cortex.
In humans, the same brain region permits abstract thinking, planning for the future and solving problems.
Previously it was believed that all cortical neurons - upper and lower layers - arose from the same stem cells, called radial glial cells (RGCs).
The new study shows that the upper layer neurons develop from a distinct population of diverse stem cells.
"Advanced functions like consciousness, thought and creativity require quite a lot of different neuronal cell types and a central question has been how all this diversity is produced in the cortex," the Daily Mail quoted Dr Santos Franco, a member of the US team from the Scripps Research Institute in La Jolla, California, as saying.
"Our study shows this diversity already exists in the progenitor cells," he said.
In mammals, the cerebral cortex is built in onion-like layers of differing thickness.
The thinner inside layers host neurons that connect to the brain stem and spinal cord to regulate essential functions such as breathing and movement.
The larger upper layers, close to the brain's outer surface, has neurons that integrate information from the senses and connect across the two halves of the brain.
Higher thinking functions are placed in the upper layers, which in evolutionary terms are the "newest" parts of the brain.
Growing stem cells in the laboratory could pave the way to better treatments for brain disorders such as schizophrenia and autism.
The new research was recently published in the journal Science.