New York:A team of researchers has developed the first scalable method to identify different subtypes of neurons in the human brain. The research lays the groundwork for "mapping" the gene activity in the human brain and could help provide a better understanding of brain functions and disorders, including Alzheimer's, Parkinson's, schizophrenia and depression. By isolating and analysing individual human brain cells, researchers identified 16 neuronal subtypes in the cerebral cortex -- the brain's outer layer of neural tissue responsible for cognitive functions including memory, attention and decision making. "We are providing a unified framework to look at and compare individual neurons, which can help us find out how many unique types of neurons exist," said Kun Zhang, bioengineering professor at University of California-San Diego. Researchers can use these different neuronal subtypes to build what Zhang calls a "reference map" of the human brain -- a foundation to understand the differences between a healthy brain and a diseased brain. "In the future, patients with brain disorders or abnormalities could be diagnosed and treated based on how they differ from the reference map. This is analogous to what's being done with the reference human genome map," Zhang noted. The team, led by University of California-San Diego, The Scripps Research Institute (TSRI) and US-based life science research company Illumina, published their findings in the journal Science.